Truck escape ramp study: final report

              Truck Escape Ramp Study i
TABLE OF CONTENTS
1. INTRODUCTION……………………………………………………………….. 1-1
1.1 Study Process………………………………………………………………………………… 1-1
2. EVALUATION OF CONDITIONS AT EXISTING TRUCK ESCAPE
RAMP (TER) SITES………………………………………………………….….
2-1
2.1 Existing, Planned and Potential Truck Escape Ramp Locations………………………….…. 2-1
2.2 As-Built Plans…………………………………………………………………………….….. 2-1
2.3 Photo Log Review……………………………………………………………………………. 2-36
2.4 Existing Truck Escape Ramp Data…………………………………………………………… 2-36
2.5 Crash Data……………………………………………………………………………………. 2-37
2.6 Conclusions……………………………………………………………………………….….. 2-37
3. DOCUMENTING THE STATE OF THE PRACTICE…………………….… 3-1
3.1 Research Process……………………………………………………………………………... 3-1
3.2 Current Practices and Standards……………………………………………………….…….. 3-1
3.2.1 Internet Research…………………………………………………………………………. 3-1
3.2.2 Federal Agencies…………………………………………………………………………. 3-2
3.2.3 Arizona Department of Transportation………………………………………………….. 3-8
3.2.4 Other State Agencies…………………………��……………………………………….. 3-29
3.2.5 Professional Society and Organization Publications…………………………………….. 3-43
3.2.6 Conclusions………………………………………………………………………………. 3-52
3.3 Conclusions………………………………………………………………………………..…. 3-53
4. EVALUATION OF CONDITIONS AT POTENTIAL TRUCK ESCAPE
RAMP (TER) LOCATIONS………………………………………………….…
4-1
4.1 Evaluation Criteria…………………………………………………………………………… 4-1
4.2 Evaluation of Potential Project Locations…………………………………………………… 4-2
4.2.1 Potential Project Location 1 – US Route 60 (MP 280): Salt River Canyon……………... 4-2
4.2.2 Potential Project Location 2 – State Route 87 SB (MP 215): Sunflower to Four- Peaks... 4-3
4.2.3 Potential Project Location 3 – State Route 87 NB (MP 230): Slate Creek……………… 4-6
4.2.4 Potential Project Location 4 – State Route 260 WB (MP 232): Verde Valley…………... 4-9
4.2.5 Potential Project Location 5 – US Route 191 SB (MP 166): Horseshoe Curve…………. 4-10
4.2.6 Potential Project Location 6 – US Route 191 NB (MP 153): Three Way……………….. 4-11
4.2.7 Potential Project Location 7 – US Route 191 NB at Smelter Hill……………………….. 4-12
4.2.8 Potential Project Location 8 – State Route 78 SB (MP 153)…………………………….. 4-12
4.2.9 Potential Project Location 9 – State Route 80 leaving Bisbee…………………………… 4-13
4.2.10 Potential Project Location 10 – State Route 83 NB (MP 42)……………………………. 4-13
4.2.11 Potential Project Location 11 – Interstate Route 8 EB (MP 20): Telegraph Pass……….. 4-15
4.2.12 Planned Project Location 1 – US Route 60 WB (MP 280)………………………………. 4-16
4.2.13 Planned Project Location 2 – State Route 68 WB (MP 5.75)……………………………. 4-16
4.3 Conclusions…………………………………………………………………………………... 4-18
Truck Escape Ramp Study ii
5. POTENTIAL TRUCK ESCAPE RAMP (TER) LOCATIONS………………. 5-1
5.1 Introduction…………………………………………………………………………………... 5-1
5.2 ADOT Criteria………………………………………………………………………………... 5-1
5.3 Crash Data Review…………………………………………………………………………… 5-2
5.4 Location Determination………………………………………………………………………. 5-6
6. SUMMARY AND RECOMMENDATIONS………………………………….. 6-1
6.1 Existing Truck Escape Ramp (TER) Sites…………………………………………………… 6-1
6.2 State of the Practice…………………………………………………………………………... 6-1
6.3 Potential Truck Escape Ramp (TER) Locations……………………………………………... 6-1
Truck Escape Ramp Study iii
LIST OF TABLES
Table No. Table Page
2.1.1 Existing, Planned and Potential TERs……………………………………………….. 2-2
2.2.1 Interstate Route 17 SB TER…………………………………………………………. 2-3
2.2.2 Interstate Route 17 NB TER………………………………………………………… 2-7
2.2.3 US Route 89 WB TER………………………………………………………………. 2-13
2.2.4 State Route 68 WB TER…………………………………………………………….. 2-17
2.2.5 State Route 68 WB TER…………………………………………………………….. 2-20
2.2.6 State Route 77 SB TER……………………………………………………………… 2-24
2.2.7 State Route 77 SB TER……………………………………………………………… 2-28
2.2.8 US Route 60 WB TER………………………………………………………………. 2-32
2.3.1 ADOT Photo Log Inventory………………………………………………………… 2-36
3.2.1 Rolling Resistance Based on Material Type………………………………………… 3-6
3.2.2 Materials Specification (ADOT)…………………………………………………….. 3-18
3.2.3 State Agency Comparison of Published Criteria…………………………………….. 3-42
3.2.4 Determination of Need and Location Scenarios…………………………………….. 3-45
4.1.1 Potentially Needed and Planned TERs………………………………………………. 4-1
4.2.1 US Route 60 WB Location…………………………………………………………... 4-2
4.2.2 State Route 87 SB Location…………………………………………………………. 4-4
4.2.3 State Route 87 NB Location……………………………………………���…………. 4-6
4.2.4 State Route 260 WB Location……………………………………………………….. 4-9
4.2.5 US Route 191 SB Location………………………………………………………….. 4-10
4.2.6 US Route 191 NB Location…………………………………………………………. 4-11
4.2.7 State Route 78 SB Location…………………………………………………………. 4-13
4.2.8 State Route 83 NB Location………………………………………………………… 4-14
4.2.9 Interstate Route 8 EB Location……………………………………………………… 4-15
4.2.10 State Route 68 WB Location………………………………………………………… 4-17
4.3.1 Summary of Potentially Needed TER Locations……………………………………. 4-19
5.3.1 Segments to be Studied Further……………………………………………………... 5-5
5.4.1 Locations for Further Evaluation……………………���……………………………. 5-8
Truck Escape Ramp Study iv
LIST OF FIGURES
Figure No. Figure Page
2.2.1 Interstate Route 17 SB TER – Typical Section……………………………………… 2-4
2.2.2 Interstate Route 17 SB TER – Plan (1 of 1)…………………………………………. 2-5
2.2.3 Interstate Route 17 SB TER – Profile (1 of 1)………………………………………. 2-6
2.2.4 Interstate Route 17 NB TER – Typical Section……………………………………... 2-8
2.2.5 Interstate Route 17 NB TER – Plan (1 of 2)………………………………………… 2-9
2.2.6 Interstate Route 17 NB TER – Plan (2 of 2)………………………………………… 2-10
2.2.7 Interstate Route 17 NB TER – Profile (1 of 2)……………………………………… 2-11
2.2.8 Interstate Route 17 NB TER – Profile (2 of 2)……………………………………… 2-12
2.2.9 US Route 89 WB TER – Typical Section……………………………���…………… 2-14
2.2.10 US Route 89 WB TER – Plan and Profile (1 of 2)………………………………….. 2-15
2.2.11 US Route 89 WB TER – Plan and Profile (2 of 2)………………………………….. 2-16
2.2.12 State Route 68 WB TER – Typical Section…………………………………………. 2-18
2.2.13 State Route 68 WB TER – Plan and Profile (1 of 1)………………………………… 2-19
2.2.14 State Route 68 WB TER – Typical Section…………………………………………. 2-21
2.2.15 State Route 68 WB TER – Plan and Profile (1 of 2)………………………………… 2-22
2.2.16 State Route 68 WB TER – Plan and Profile (2 of 2)………………………………… 2-23
2.2.17 State Route 77 SB TER – Typical Section…………………………………………... 2-25
2.2.18 State Route 77 SB TER – Plan and Profile (1 of 2)…………………………………. 2-26
2.2.19 State Route 77 SB TER – Plan and Profile (2 of 2)…��……………………………. 2-27
2.2.20 State Route 77 SB TER – Typical Section………………………………………….. 2-29
2.2.21 State Route 77 SB TER – Plan and Profile (1 of 2)…………………………………. 2-30
2.2.22 State Route 77 SB TER – Plan and Profile (2 of 2)…………………………………. 2-31
2.2.23 US Route 60 WB TER – Typical Section…………………………………………… 2-33
2.2.24 US Route 60 WB TER – Plan and Profile (1 of 2)………………………………….. 2-34
2.2.25 US Route 60 WB TER – Plan and Profile (2 of 2)………………………………….. 2-35
3.2.1 Dragnet Arresting Barriers (John Thomas, Inc.)…………………………………….. 3-2
3.2.2 W7-1 Sign Series (MUTCD)………………………………………………………… 3-3
3.2.3 W7-2 and W7-3 Sign Series (MUTCD)……………………………………………... 3-3
3.2.4 W7-4 Sign Series (MUTCD)……………………���………………………………… 3-4
3.2.5 Plan and Profile (AASHTO Figure 3-72)…………………………………………… 3-7
3.2.6 Determination of Need (ADOT Figure 209.4A)…………………………………….. 3-8
3.2.7 Plan and Typical Section (ADOT Figure 208.4B)…………………………………... 3-9
3.2.8 Relationship between Percent and Miles of Downgrade (ADOT)………………….. 3-15
3.2.9 Desired Alignment for Truck Escape Ramp (ADOT)………………………………. 3-16
3.2.10 Wrecker Anchor Detail (ADOT)……………………………………………………. 3-17
3.2.11 Standard Drawing 4-M-1.25 (ADOT)……………………………………………….. 3-20
3.2.12 Standard Drawing 4-S-1.16 (ADOT)………………………………………………... 3-20
3.2.13 Standard Drawing 4-S-1.06 (ADOT)………………………………………………... 3-21
3.2.14 US Route 60 CLOSE Report Plan and Profile (ADOT)…………………………….. 3-26
3.2.15 US Route 60 Project Assessment (PA) Typical Section (ADOT).………………….. 3-27
Truck Escape Ramp Study v
3.2.16 US Route 60 Project Assessment (PA) Plan and Profile (ADOT)…………………... 3-28
3.2.17 Guidelines for TER Need on New Highways (Caltrans)……………………………. 3-31
3.2.18 Typical Runaway Truck Ramp Signing and Marking (Caltrans)…………………… 3-32
3.2.19 Montana Route 287 Truck Escape Ramp Typical Section (MDT)………………….. 3-34
3.2.20 Montana Route 287 Truck Escape Ramp Plan and Profile (MDT)…………………. 3-34
3.2.21 Interstate Route 90 Truck Escape Ramp Typical Section (MDT)…………………... 3-35
3.2.22 Interstate Route 90 Truck Escape Ramp Plan and Profile 1 (MDT)………………… 3-35
3.2.23 Interstate Route 90 Truck Escape Ramp Plan and Profile 2 (MDT)………………… 3-36
3.2.24 State Route 163 Truck Escape Ramp Typical Section (NDOT)…………………….. 3-37
3.2.25 State Route 163 Truck Escape Ramp Plan (NDOT)………………………………… 3-37
3.2.26 State Route 163 Truck Escape Ramp Profile (NDOT)……………………………… 3-38
3.2.27 Escape Ramp Layout (SDDOT Figure 6-19)………………………………………... 3-39
3.2.28 Typical Emergency Escape Ramp Plan and Profile (WSDOT Figure 1010-8)……... 3-41
3.2.29 State Route 28 Truck Escape Ramp Plan and Profile (NYDOT)…………………… 3-48
5.2.1 Determination of Need (ADOT Figure 209.4A)…………………………………….. 5-2
5.3.1 Segment to be Studied Further………………………………………………………. 5-4
5.4.1 Areas to be Evaluated Further……………………………………………………….. 5-7
Truck Escape Ramp Study 1-1
Chapter 1
Introduction
1.1 Study Process
In recent years, several requests have originated from Arizona Department of Transportation
(ADOT) District offices regarding the installation of truck escape ramps (TERs) along specific
routes within their districts. At the time, the ADOT Highway Construction program did not
include specific projects for the construction of TERs. In response to these requests, ADOT
Management decided to collect grade data, horizontal curve data, general site data, traffic data
and accident data at existing, planned and potential TER sites. The data was to be compiled into
a report format that presented the conditions at existing TER locations as well as those at planned
and potential locations. In addition, a review of existing ADOT policy, as well as that of other
mountainous states, was to be undertaken to confirm the current state of the practice.
Through every step of the process, ADOT personnel were involved in the decision-making
process and format the report was to take. The Priority Programming Manager of the
Transportation Planning Division served as the ADOT project manager, with assistance and
input provided by the State Traffic Engineer and State Roadway Engineer.
The following chapters lay out an analysis of existing locations within Arizona and the relevant
data that was collected, present a review of current policy within Arizona and throughout the
country, and investigate potential locations for future TER sites based on requests from various
District Engineers and Geographic Information Systems (GIS) analysis. The information
presented in this report is intended to assist ADOT in the implementation of additional TERs in
future highway construction programs, with the possibility of using Hazard Elimination and
Safety (HES) funding when and where appropriate.
Truck Escape Ramp Study 2-1
Chapter 2
Evaluation of Conditions at Existing
Truck Escape Ramp (TER) Sites
2.1 Existing, Planned and Potential Truck Escape Ramp Locations
The purpose of the data gathering process was to better understand existing conditions, current
policies, procedures and design criteria used within Arizona for their truck escape ramps (TERs).
This knowledge will be a major part of the Arizona Department of Transportation’s (ADOT)
efforts to provide effective TER facilities in the future.
Data collection included; 1) identifying where ADOT currently has TERs, 2) finding out if there
are locations where it may be beneficial to provide a future TER (falling in two categories, a)
may be beneficial and b) are currently in the planning process), 3) collecting as-built plans for
those areas where there are existing TERs to quantify the design layout, 4) reviewing the photo
log of the existing TERs to verify that they have been maintained as originally built, and 5)
collecting crash data for those areas where there are existing TERs to evaluate if there is an
accident history.
The data presented below was obtained from five primary resources, as indicated below:
• ADOT District Engineers and/or their designee’s,
• As-Built Plans,
• ADOT Photo Log,
• ADOT Existing TER Data, and
• Crash Data.
In total, nine District Engineers representing all the ADOT Construction Districts and Reed
Henry, manager of the Traffic HES Section, were contacted. Each representative was asked to
provide information about existing TERs, where TERs may be needed in the future, and
locations where there were TERs being planned. Table 2.1.1 illustrates our findings.
2.2 As-Built Plans
The available as-built plans were collected for the existing TERs. Plans were also collected for
the length of the downgrade associated with the TER. Table 2.1.1 summarizes the existing,
planned and potential TERs within the State. Detailed information pertaining to each individual
TER is supplied in Table 2.2.1 through Table 2.2.8 and Figure 2.2.1 through Figure 2.2.25.
Truck Escape Ramp Study 2-2
Table 2.1.1
Existing, Planned and Potential TERs
District Existing TERs Potentially Needed TERs Planned TERs
Flagstaff I-17 SB, MP 300.37
US 89 SB, MP 524.26
None
Globe US 60 WB, MP 228.11
SR 77 SB, MP 154.2
SR 77 SB, MP 155.7
US 60 MP 280 (Salt River
Canyon)
US 60 WB, MP 280+
Holbrook None None None
Kingman SR 68 WB, MP 1.29 None SR 68 WB, moved to MP
5.75
Phoenix None SR 87 Sunflower to 4-Peaks None
Prescott I-17 NB, MP 283.07
SR 87 NB into Slate Creek
SR 260 WB into Verde Valley
None
Safford SR 80 EB, into Bisbee2 US 191 SB at Horseshoe Curve
US 191 NB to Three Way
US 191 NB at Smelter Hill
SR 78 SB MP 153
SR 80 leaving Bisbee
None
Tucson None SR 83 NB, MP 42 None
Yuma None I-8 EB, MP 20 (Telegraph Pass) None
TOTAL 8 11 2
1 Indicates TERs not found at ADOT Engineering Records, but on record with Traffic HES Section.
2 Indicates TERs not found at ADOT Engineering Records. May have been built by a mining company.
Truck Escape Ramp Study 2-3
Table 2.2.1
Interstate Route 17 SB TER
Interstate Route 17 SB TER, I-17 MP 300.37
Variable Description
Mainline Station, Begin TER 5268+50.00
Type of TER Descending Grade Arrester Bed
Exits Right side of roadway, on tangent
Length 2844 feet total length
740 feet exit ramp terminal
1884 feet of arrester bed
220 feet of secondary retarder and slopes
Width Arrester bed varies from 40 feet at point of entry to 26 over
roughly 400 feet.
Anchors Each side of ramp @ 300 foot intervals
Service Road 12 foot wide, paved, between TER and roadway
Grade of TER -2.000%
Aggregate (if any) Unspecified
Depth of Aggregate Tapers from 6” at entry to 24” in 400’, maintains 24” for 900’,
tapers from 24” to 36” in 200’, maintains 36” for final 380 feet.
Aggregate Liner 4” CTB
“Last Chance” device 35’W x 29’D x 8’H aggregate mound (1 ½:1 slopes)
Entering Horizontal Curve Data
(Tangent sections not shown)
Sta. 5550+00.00 – Sta. 5443+51.93 on Tangent (28,200’ prior)
Sta. 5437+23.46, R = 11,459.16’Lt, L = 629.10’ (16,900’ prior)
Sta. 5402+88.97, R+o = 2,867.12’Rt, L = 1,429.30’ (13,400’ prior)
Sta. 5387+46.82, R+o = 2867.12’Lt, L = 1181.67’ (11,900’ prior)
Sta. 5371+82.44, R+o = 5729.89’Lt, L = 862.92’ (10,300’ prior)
Sta. 5353+10.50, R+o = 2867.12’Rt, L = 1086.97’ (8,500’ prior)
Sta. 5330+99.67, R+o = 2867.12’Lt, L = 1102.22’ (6,200’ prior)
Sta. 5320+46.87, R+o = 4584.23’Rt, L = 843.33’ (5,200’ prior)
Sta. 5311+25.20, R+o = 2296.37’Lt, L = 1000’ (4,300’ prior)
Sta. 5296+60.60, R+o = 3820.70’Lt, L = 826.11’ (2,800’ prior)
Sta. 5283+46.66, R+o = 2296.37’Rt, L = 1628.00’ (1,500’ prior)
Sta. 5268+50.00 – Truck Escape Ramp
Sta. 5262+55.59, R+o = 2867.12’Lt, 1045.42’ (600’ after)
Sta. 5225+76.43, R+o = 2549.79’Lt, 2706.54’ (4,300’ after)
Entering Vertical Geometry Sta. 5545+50, -3.400% (27,700’ prior)
Sta. 5521+00, -4.222% (25,300’ prior)
Sta. 5502+00, -1.7815% (23,400’ prior)
Sta. 5469+50, -6.00% (20,100’ prior)
Sta. 5449+50, -4.2387% (18,100’ prior)
Sta. 5441+00, -5.6363% (17,300’ prior)
Sta. 5430+00, -2.6925% (16,200’ prior)
Sta. 5396+50, -4.00% (12,700’ prior)
Sta. 5375+00, -5.6700% (10,700’ prior)
Sta. 5366+00, -3.3043% (9,800’ prior)
Sta. 5324+00, -4.0997% (5,500’ prior)
Sta. 5292+00, -6.00% (2,400’ prior)
Sta. 5268+50 – Truck Escape Ramp
Sta. 5225+00, -5.011% (4,400’ after)
Sta. 5215+00, -4.2126% (5,400’ after)
Sta. 5192+00, -1.5882% (7,700’
Truck Escape Ramp Study 2-4
Length of Mountain Grade Above Greater than 27,700’ (5.25 mi)
Length of Mountain Grade Below Greater than 7,650’ (1.45 mi)
Average Percent Grade of Mountain Above -4.64% over 27,700’
Annual Average Daily Traffic (AADT) 25,294 (Year 2000)
Percent Trucks 17.8% (Year 2000)
Average Number of Accidents per Year 15.8 Total, 1.2 Tractor-Trailer
TER Usage Data Collected Between 10/22/1988 through 06/02/2000
Total Number of Uses 44
Total Number of Warranted Uses1 34
Conditions at Bottom of Grade System Interchange (SR 179 (Sedona))
1Warranted uses include brake failure, overheating and/or smoking brakes, failure to downshift properly and loss of air pressure in braking
mechanism.
Figure 2.2.1
Interstate Route 17 SB TER – Typical Section
Truck Escape Ramp Study 2-5
Figure 2.2.2
Interstate Route 17 SB TER – Plan (1 of 1)
Truck Escape Ramp Study 2-6
Figure 2.2.3
Interstate Route 17 SB TER – Profile (1 of 1)
Truck Escape Ramp Study 2-7
Table 2.2.2
Interstate Route 17 NB TER
Interstate Route 17 NB TER, I-17 MP 283.07
Variable Description
Mainline Station, begin TER 4290+00.00
Type of TER Ascending Grade Arrester bed
Exits Left side of roadway
Length 2560 feet total length
1460 feet exit ramp terminal
1100 feet of arrester bed including secondary retarder
Width Arrester bed varies from 40 feet at point of entry to 26 over
roughly 400 feet.
Anchors Each side of ramp @ 300 foot intervals
Service Road 12 foot wide, paved, between TER and roadway
Grade of TER +2.000%
Aggregate (if any) Pea gravel
Depth of Aggregate Tapers from 6” at entry to 24” in 550’, maintains 24” for final
550 feet.
Aggregate Liner Subgrade
“Last Chance” device 26’W x 39.5’D x 5’H aggregate mound (varying slopes)
Entering Horizontal Curve Data
(Tangent sections not shown.)
Sta. 4130+81.49, R+o = 2812.17’Rt, L = 3780.28’ (15,900’ prior)
Sta. 4162+73.25, R+o = 2292.97’Lt, L = 1293.24’ (12,700’ prior)
Sta. 4182+13.00, R+o = 1640.14’Rt, L = 1845.24’ (10,800’ prior)
Sta. 4211+72.76, R+o = 1640.14’Lt, L = 2107.62’ (7,800’ prior)
Sta. 4225+83.57, R = 4583.66’Rt, L = 547.78’ (6,400’ prior)
Sta. 4235+96.39, R+o = 1640.14’Lt, L = 1103.61’ (5,400’ prior)
Sta. 4252+97.27, R+o = 1640.14’Rt, L = 1328.57’ (3,700’ prior)
Sta. 4278+36.73, R = 4583.66’Lt, L = 1632.00’ (1,200’ prior)
Sta. 4290+00.00 – Truck Escape Ramp
Sta. 4297+40.06, R+o = 1640.14’Rt, L = 1739.52’ (700’ after)
Sta. 4313+04.90, R = 1640.14’Lt, L = 1303.16’ (2,300’ after)
Sta. 4354+32.29, R = 2865.37’Lt, L = 4014.76’ (6,400’ after)
Entering Vertical Geometry Sta. 4165+00, -2.8043% (12,500’ prior)
Sta. 4184+00, -5.9062% (10,600’ prior)
Sta. 4200+00, -6.0000% (9,000’ prior)
Sta. 4227+00, -5.8000% (6,300’ prior)
Sta. 4247+00, -6.4200% (4,300’ prior)
Sta. 4252+00, -5.6000% (3,800�� prior)
Sta. 4260+00, -5.8000% (3,000’ prior)
Sta. 4290+00 – Truck Escape Ramp
Sta. 4300+00, -4.6000% (1,000’ after)
Sta. 4360+00, -5.2024% (7,000’ after)
Sta. 4394+00, -0.9366% (10,400’ after)
Length of Mountain Grade Above 12,500’ (2.37 mi)
Length of Mountain Grade Below 10,400’ (1.97 mi)
Average Percent Grade of Mountain Above -5.44% over 12,500’
Annual Average Daily Traffic (AADT) 20,180 (Year 2000)
Percent Trucks 21.7% (Year 2000)
Truck Escape Ramp Study 2-8
Average Number of Accidents per Year 11.8 Total, 0.8 Tractor-Trailer
TER Usage Data Collected Between 03/16/1986 through 02/25/2001
Total Number of Uses 51
Total Number of Warranted Uses1 19
Conditions at Bottom of Grade System Interchange
1 Warranted uses include brake failure, overheating and/or smoking brakes, failure to downshift properly and loss of air pressure in braking
mechanism.
Figure 2.2.4
Interstate Route 17 NB TER – Typical Section
Truck Escape Ramp Study 2-9
Figure 2.2.5
Interstate Route 17 NB TER – Plan (1 of 2)
Truck Escape Ramp Study 2-10
Figure 2.2.6
Interstate Route 17 NB TER – Plan (2 of 2)
Truck Escape Ramp Study 2-11
Figure 2.2.7
Interstate Route 17 NB TER – Profile (1 of 2)
Truck Escape Ramp Study 2-12
Figure 2.2.8
Interstate Route 17 NB TER – Profile (2 of 2)
Truck Escape Ramp Study 2-13
Table 2.2.3
US Route 89 WB TER
U.S. Route 89 WB TER, SR 89 MP 524.26
Variable Description
Mainline Station begin TER 178+21.38
Type of TER Descending Grade Arrester Bed
Exits Right side of roadway
Length 1965 feet total length
660 feet exit ramp terminal
1230 feet of arrester bed
75 feet of secondary retarder and slopes
Width Arrester bed varies from 40 feet at point of entry to 26 over
roughly 400 feet.
Anchors Each side of ramp @ 300 foot intervals
Service Road 12 foot wide, paved, outside TER away from roadway
Grade of TER Varies from –3.64% to –3.44% to –1.61% to –3.35%.
Aggregate (if any) Pea gravel
Depth of Aggregate Tapers from 12” at entry to 24” in 400’, maintains 24” for final
830 feet.
Aggregate Liner Compacted subgrade
“Last Chance” device 26’W x 17’D x 5’H aggregate mound (1 ½:1 slopes)
Entering Horizontal Curve Data
(Tangent sections not shown)
Sta. 377+19.40, R+o = 998.66’Rt, L = 1783.00’ (19,900’ prior)
Sta. 360+33.6, R+o = 957.44’Lt, L = 1218.5’ (18,200’ prior)
Sta. 342+43.80, R+o = 957.44’Lt, L = 768.8’ (16,400’ prior)
Sta. 333+77.5, R+o = 955.56’Lt, L = 782.7’ (15,600’ prior)
Sta. 327+37.3, R+o = 1146.28’Rt, L = 400.0’ (14,900’ prior)
Sta. 322+22.5, R+o = 2864.79’Lt, L = 385.0’ (14,400’ prior)
Sta. 314+69.4, R+o = 956.34’Lt, L = 523.1’ (13,600’ prior)
Sta. 307+24.5, R+o = 956.34’Rt, L = 906.4’ (12,900’ prior)
Sta. 297+11.1, R+o = 1147.37’Lt, L = 911.0’ (11,900’ prior)
Sta. 290+01.9, R+o = 1147.37’Rt, L = 420.00’ (11,200’ prior)
Sta. 280+37.8, R+o = 1433.14’Rt, L = 878.34’ (10,200’ prior)
Sta. 269+15.8, R+o = 955.56’Lt, L = 868.1’ (9,100’ prior)
Sta. 261+15.3, R+o = 955.56’Rt, L = 626.7’ (8,300’ prior)
Sta. 252+87.5, R+o = 955.56’Lt, L = 1060.7’ (7,500’ prior)
Sta. 237+41.0, R+o = 957.44’Rt, L = 1610.4’ (5,900’ prior)
Sta. 218+70.3, R+o = 1433.74’Rt, L = 948.3’ (4,000’ prior)
Sta. 209+39.8, R+o = 1433.14’Rt, L = 854.6’ (3,100’ prior)
Sta. 178+21.38 – Truck Escape Ramp
Sta. 205+05.4 – Sta. 158+55.7 on Tangent
Entering Vertical Geometry
Sta. 381+00, -6.00% (20,300’ prior)
Sta. 365+50, -2.00% (18,700’ prior)
Sta. 353+00, -6.00% (17,500’ prior)
Sta. 329+00, -4.00% (15,100’ prior)
Sta. 318+00, -4.80% (14,000’ prior)
Sta. 305+00, -6.00% (12,700’ prior)
Sta. 274+00, -3.70% (9,600’ prior)
Sta. 255+00, -6.00% (7,700’ prior)
Sta. 222+00, -1.40% (4,400’ prior)
Sta. 210+00, -5.00% (3,200’ prior)
Sta. 185+00, -3.80% (700’ prior)
Sta. 178+21.38 – Truck Escape Ramp
Sta. 170+00, -2.60% (800’ after)
Truck Escape Ramp Study 2-14
Length of Mountain Grade Above 20,300’ (3.84 mi)
Length of Mountain Grade Below Greater than 800’ (0.15 mi)
Average Percent Grade of Mountain Above -4.85% over 20,300’ (3.84 mi)
Annual Average Daily Traffic (AADT) 3,304 (Year 2000)
Percent Trucks 15.1% (Year 2000)
Average Number of Accidents per Year 9.6 Total, 0.8 Tractor-Trailer
TER Usage Data Collected Between
Total Number of Uses
Total Number of Warranted Uses1
NO DATA ON RECORD.
Conditions at Bottom of Grade Intersection with US Route 89A
1 Warranted uses include brake failure, overheating and/or smoking brakes, failure to downshift properly and loss of air pressure in braking
mechanism.
Figure 2.2.9
US Route 89 WB TER – Typical Section
Truck Escape Ramp Study 2-15
Figure 2.2.10
US Route 89 WB TER – Plan and Profile (1 of 2)
Truck Escape Ramp Study 2-16
Figure 2.2.11
US Route 89 WB TER – Plan and Profile (2 of 2)
Truck Escape Ramp Study 2-17
Table 2.2.4
State Route 68 WB TER
State Route 68 WB TER, SR 68 MP 1.29
Variable Description
Mainline Station begin TER 92+50.00 (From DCR)
Type of TER Descending Grade Arrester Bed
Exits Right side of roadway
Length 2500 feet total length
973 feet exit ramp terminal
1327 feet of arrester bed including secondary retarder
200 feet service road return
Width Arrester bed varies from 40 feet at point of entry to 26 over
roughly 400 feet.
Anchors Each side of ramp @ 200 foot intervals
Service Road 12 foot wide, paved, outside TER away from roadway
Grade of TER -4.1189%
Aggregate (if any) Yes, unspecified
Depth of Aggregate Tapers from 6” at entry to 48” in 150’, maintains 48” for final
1177 feet.
Aggregate Liner Asphalt concrete and engineering fabric
“Last Chance” device 26’W x 17’D x 5’H aggregate mound (1 ½:1 slopes)
Entering Horizontal Curve Data
(Tangent sections not shown.)
Sta. 656+17.56, R = 3819.72’Rt, L = 768.88’ (56400’ prior)
Sta. 641+21.10, R = 5729.58’Lt, L = 600.48’ (54900’ prior)
Sta. 626+86.91, R = 5729.58’Lt, L = 756.27’ (53400’ prior)
Sta. 610+88.47, R = 2864.79’Rt, L = 596.40’ (51800’ prior)
Sta. 599+48.71, R+o = 1208.22’Lt, L = 1074.40’ (50700’ prior)
Sta. 554+65.15, R = 11459.16’Rt, L = 859.58’ (46200’ prior)
Sta. 533+41.92, R+o = 1433.37’Rt, L = 3303.77’ (44100’ prior)
Sta. 501+03.03, R+o = 1911.82’Lt, L = 738.07’ (40900’ prior)
Sta. 473+19.62, R+o = 1209.76’Lt, L = 1555.96’ (38100’ prior)
Sta. 444+18.32, R = 2864.79’Rt, L = 879.67’ (35200’ prior)
Sta. 423+83.92, R = 2864.79’Lt, L = 1167.13’ (33100’ prior)
Sta. 365+92.73, R = 2546.48’Rt, L = 1583.54’ (27300’ prior)
Sta. 253+11.72, R = 7639.44’Lt, L = 1158.42’ (16100’ prior)
Sta. 236+41.45, R+o = 1910.73’Rt, L = 1277.77’ (14400’ prior)
Sta. 201+26.24, R = 11459.16’Lt, L = 724.11’ (10900’ prior)
Sta. 171+00.54, R = 2864.79’Lt, L = 1028.75’ (7900’ prior)
Sta. 151+37.23, R = 11459.16’Lt, L = 918.54’ (5900’ prior)
Sta. 102+85.77, R = 2864.79’Rt, L = 760.98’ (1000’ prior)
Sta. 92+50.00 – Truck Escape Ramp
Sta. 73+52.18, R+o = 1910.73’Rt, L = 824.65’ (1900’ after)
Entering Vertical Geometry Sta. 650+40, -6.0000% (55800’ prior)
Station Equation: 576+28.18Bk = 592+92.71Ahd (48400’ prior)
Sta. 560+00, -4.7039% (46800’ prior)
Sta. 540+00, -5.9524% (44800’ prior)
Sta. 519+00, -5.5526% (42700’ prior)
Sta. 500+00, -4.8306% (40800’ prior)
Sta. 466+00, -5.0600% (37400’ prior)
Sta. 445+00, -3.6326% (35300’ prior)
Sta. 427+50, -5.1693% (33500’ prior)
Sta. 395+00, -5.9732% (30300’ prior)
Sta. 355+00, -4.9291% (26300’ prior)
Sta. 284+50, -2.7778% (19200’ prior)
Sta. 275+50, -4.4000% (18300’ prior)
Truck Escape Ramp Study 2-18
Sta. 255+50, -3.0000% (16300’ prior)
Sta. 244+50, -6.0000% (15200’ prior)
Sta. 226+50, -4.3947% (13400’ prior)
Sta. 207+50, -5.0491% (11500’ prior)
Sta. 180+00, -5.5361% (8800’ prior)
Sta. 162+00, -5.0762% (6800’ prior)
Sta. 151+50, -4.5826% (5900’ prior)
Sta. 140+00, -4.8850% (4800’ prior)
Sta. 120+00, -3.7075% (2800’ prior)
Sta. 112+00, -5.0876% (2000’ prior)
Sta. 92+50 – Truck Escape Ramp
Sta. 87+00, -3.7713% (600’ after)
Length of Mountain Grade Above 55,790 feet (10.57 mi)
Length of Mountain Grade Below Greater than 600’ (0.11 mi)
Average Percent Grade of Mountain Above -5.11% over 55,790’ (10.57 mi)
Annual Average Daily Traffic (AADT) 8,201 (Year 2000)
Percent Trucks 4.5% (Year 2000)
Average Number of Accidents per Year 8.1 Total, 0.5 Tractor-Trailer
TER Usage Data Collected Between 07/27/1986 through 05/01/1996
Total Number of Uses 25
Total Number of Warranted Uses1 22
Conditions at Bottom of Grade Intersection
1 Warranted uses include brake failure, overheating and/or smoking brakes, failure to downshift properly and loss of air pressure in braking
mechanism.
Figure 2.2.12
State Route 68 WB TER – Typical Section
Truck Escape Ramp Study 2-19
Figure 2.2.13
State Route 68 WB TER – Plan and Profile (1 of 1)
Truck Escape Ramp Study 2-20
Table 2.2.5
State Route 68 WB TER
State Route 68 TER, SR 68 MP 5.75 (New Design/Build)
Variable Description
Mainline Station begin TER 303+67.55
Type of TER Descending Grade Arrester Bed
Exits Right side of roadway
Length 2495 feet total length
900 feet exit ramp terminal
1285 feet of arrester bed including secondary retarder
310 feet service road return
Width Arrester bed width of 34 feet throughout.
Anchors Each side of ramp @ 150 foot intervals
Service Road 13.5 foot wide (including anchors), paved, between TER and
roadway
Grade of TER Varies from -4.4492% to –2.3283%
Aggregate (if any) Unspecified, reused from original TER
Depth of Aggregate Tapers from 6” at entry to 36” in 150’, maintains 36” for final
1111 feet.
Aggregate Liner 3” asphalt concrete lining
“Last Chance” device 34’W x 17’D x 5’H aggregate mound (1 ½:1 slopes)
Entering Horizontal Curve Data
(Tangent sections not shown.)
Sta. 656+17.56, R = 3819.72’Rt, L = 768.88’ (35300’ prior)
Sta. 641+21.10, R = 5729.58’Lt, L = 600.48’ (33800’ prior)
Sta. 626+86.91, R = 5729.58’Lt, L = 756.27’ (32300’ prior)
Sta. 610+88.47, R = 2864.79’Rt, L = 596.40’ (30700’ prior)
Sta. 599+48.71, R+o = 1208.22’Lt, L = 1074.40’ (29600’ prior)
Sta. 554+65.15, R = 11459.16’Rt, L = 859.58’ (25100’ prior)
Sta. 533+41.92, R+o = 1433.37’Rt, L = 3303.77’ (23000’ prior)
Sta. 501+03.03, R+o = 1911.82’Lt, L = 738.07’ (19700’ prior)
Sta. 473+19.62, R+o = 1209.76’Lt, L = 1555.96’ (17000’ prior)
Sta. 444+18.32, R = 2864.79’Rt, L = 879.67’ (14100’ prior)
Sta. 423+83.92, R = 2864.79’Lt, L = 1167.13’ (12000’ prior)
Sta. 365+92.73, R = 2546.48’Rt, L = 1583.54’ (6200’ prior)
Sta. 303+67.55 – Truck Escape Ramp
Sta. 253+11.72, R = 7639.44’Lt, L = 1158.42’ (5100’ after)
Sta. 236+41.45, R+o = 1910.73’Rt, L = 1277.77’ (6700’ after)
Sta. 201+26.24, R = 11459.16’Lt, L = 724.11’ (10200’ after)
Sta. 171+00.54, R = 2864.79’Lt, L = 1028.75’ (13300’ after)
Sta. 151+37.23, R = 11459.16’Lt, L = 918.54’ (15200’ after)
Sta. 102+85.77, R = 2864.79’Rt, L = 760.98’ (20100’ after)
Sta. 73+52.18, R+o = 1910.73’Rt, L = 824.65’ (23000’ after)
Entering Vertical Geometry Sta. 650+40, -6.0000% (34700’ prior)
Station Equation: 576+28.18Bk = 592+92.71Ahd (27300’ prior)
Sta. 560+00, -4.7039% (25600’ prior)
Sta. 540+00, -5.9524% (23600’ prior)
Sta. 519+00, -5.5526% (21500’ prior)
Sta. 500+00, -4.8306% (19600’ prior)
Sta. 466+00, -5.0600% (16200’ prior)
Sta. 445+00, -3.6326% (14100’ prior)
Sta. 427+50, -5.1693% (12400’ prior)
Sta. 395+00, -5.9732% (9100’ prior)
Sta. 355+00, -4.9291% (5100’ prior)
Sta. 303+67 – Truck Escape Ramp
Sta. 284+50, -2.7778% (1900’ after)
Truck Escape Ramp Study 2-21
Sta. 275+50, -4.4000% (2800’ after)
Sta. 255+50, -3.0000% (4800’ after)
Sta. 244+50, -6.0000% (5900’ after)
Sta. 226+50, -4.3947% (7700’ after)
Sta. 207+50, -5.0491% (9600’ after)
Sta. 180+00, -5.5361% (12400’ after)
Sta. 162+00, -5.0762% (14400’ after)
Sta. 151+50, -4.5826% (15200’ after)
Sta. 140+00, -4.8850% (16400’ after)
Sta. 120+00, -3.7075% (18400’ after)
Sta. 112+00, -5.0876% (19200’ after)
Sta. 87+00, -3.7713% (21700’ after)
Length of Mountain Grade Above 34,700 feet (6.57 mi)
Length of Mountain Grade Below Greater than 21,700 feet (4.11 mi)
Average Percent Grade of Mountain Above -5.34% over 34,700’ (6.57 mi)
Annual Average Daily Traffic (AADT) 8,201 (Year 2000)
Percent Trucks 4.5% (Year 2000)
Average Number of Accidents per Year 8.1 Total, 0.5 Tractor-Trailer
TER Usage Data Collected Between
Total Number of Uses
Total Number of Warranted Uses1
NEW LOCATION, NO DATA ON RECORD.
Conditions at Bottom of Grade Intersection
1 Warranted uses include brake failure, overheating and/or smoking brakes, failure to downshift properly and loss of air pressure in braking
mechanism.
Figure 2.2.14
State Route 68 WB TER – Typical Section
Truck Escape Ramp Study 2-22
Figure 2.2.15
State Route 68 WB TER – Plan and Profile (1 of 2)
Truck Escape Ramp Study 2-23
Figure 2.2.16
State Route 68 WB TER – Plan and Profile (2 of 2)
Truck Escape Ramp Study 2-24
Table 2.2.6
State Route 77 SB TER
State Route 77 SB TER, SR 77 MP 154.2
Variable Description
Mainline Station begin TER 3197+47.05
Type of TER Descending Grade Arrester Bed
Exits Right side of roadway
Length 2704 feet total length
1700 feet exit ramp terminal
1004 feet of arrester bed including secondary retarder
Width Arrester bed width of 34 feet throughout.
Anchors Service road side of ramp @ 150 foot intervals
Service Road 13.5 foot wide (including anchors), paved, between TER and
roadway
Grade of TER Varies from –7.9500% to –1.2500%
Aggregate (if any) Unspecified
Depth of Aggregate Tapers from 6” at entry to 36” in 150’, maintains 36” for final
854 feet.
Aggregate Liner 4” CTB
“Last Chance” device 26’W x 20’D x 5’H aggregate mound (1 ½:1 slopes)
Entering Horizontal Curve Data
(Tangent sections not shown.)
Sta. 3422+27.48, R = 954.93’Lt, L = 791.53’ (22,500’ prior)
Sta. 3409+55.14, R = 2291.83’Lt, L = 780.00’ (21,200‘ prior)
Sta. 3397+79.93, R = 716.20’Rt, L = 943.09’ (20,000‘ prior)
Sta. 3388+49.77, R = 716.20’Lt, L = 807.85’ (19,100‘ prior)
Sta. 3379+91.88, R = 1432.40’Rt, L = 707.92’ (18,200‘ prior)
Sta. 3369+66.09, R = 2289.83’Lt, L = 1243.67’ (17,200‘ prior)
Sta. 3356+52.15, R = 1432.40’Lt, L = 700.21’ (15,900‘ prior)
Sta. 3348+23.73, R = 954.93’Rt, L = 934.17’ (15,100‘ prior)
Sta. 3337+60.11, R = 1432.40’Lt, L = 1093.27’ (14,000‘ prior)
Sta. 3329+30.84, R = 954.93’Rt, L = 525.40’ (13,200‘ prior)
Sta. 3320+37.13, R = 716.20’Rt, L = 971.18’ (12,300‘ prior)
Sta. 3310+61.13, R = 954.93’Lt, L = 940.83’ (11,300‘ prior)
Sta. 3284+75.37, R = 954.93’Lt, L = 906.62’ (8,700‘ prior)
Sta. 3265+58.40, R = 2291.83’Rt, L = 550.00’ (6,800‘ prior)
Sta. 3256+82.58, R = 954.93’Lt, L = 997.78’ (5,900‘ prior)
Sta. 3245+72.13, R = 2291.83’Rt, L = 452.78’ (4,800‘ prior)
Sta. 3236+77.57, R = 954.93’Lt, L = 755.00’ (3,900‘ prior)
Sta. 3227+32.76, R = 954.93’Rt, L = 1034.63’ (3,000‘ prior)
Sta. 3206+28.54, R = 1909.86’Lt, L = 600.86’ (900‘ prior)
Sta. 3197+47.05 – Truck Escape Ramp
Sta. 3195+58.54, R = 1432.40’Rt, L = 1336.81’ (200‘ after)
Sta. 3178+34.92, R = 1637.02’Lt, L = 2013.01’ (1,900‘ after)
Sta. 3143+06.54, R = 2864.79’Lt, L = 1401.94’ (5,400‘ after)
Sta. 3038+04.88, R = 5729.58’Rt, L = 2275.28’ (15,900‘ after)
Entering Vertical Geometry Sta. 3423+00, -5.0000% (22,600‘ prior)
Sta. 3410+50, -0.3510% (21,300‘ prior)
Sta. 3400+50, -7.9850% (20,300‘ prior)
Sta. 3381+50, -3.4290% (18,400‘ prior)
Sta. 3373+50, -7.1000% (17,600‘ prior)
Sta. 3340+00, -4.0000% (14,300‘ prior)
Sta. 3333+50, +1.1667% (13,600‘ prior)
Sta. 3321+50, -8.0000% (12,400‘ prior)
Sta. 3309+50, +1.5440% (11,200‘ prior)
Sta. 3300+50, -6.6000% (10,300’ prior)
Truck Escape Ramp Study 2-25
Sta. 3264+00, -8.0000% (6,700‘ prior)
Sta. 3233+00, -5.8571% (3,600‘ prior)
Sta. 3226+00, -6.0000% (2,900‘ prior)
Sta. 3208+00, -8.0000% (1,100‘ prior)
Sta. 3197+47.05 – Truck Escape Ramp
Sta. 3175+00, -6.0000% (2,200‘ after)
Sta. 3154+50, -1.5135% (4,300’ after)
Sta. 3136+00, +2.5000% (6,100‘ after)
Sta. 3130+00, +0.7222% (6,700‘ after)
Sta. 3112+00, -3.3889% (8,500‘ after)
Sta. 3094+50, +0.8400% (10,300‘ after)
Sta. 3082+00, -2.8333% (11,500‘ after)
Sta. 3065+00, -3.8462% (13,200‘ after)
Sta. 3052+00, -7.0000% (14,500‘ after)
Sta. 3043+00, -2.5000% (15,400‘ after)
Sta. 3035+00, -3.6153% (16,200‘ after)
Sta. 3022+00, -3.0714%, (17,500‘ after)
Length of Mountain Grade Above Greater than 22,600’ (4.28 mi)
Length of Mountain Grade Below Greater than 17,500’ (3.31 mi)
Average Percent Grade of Mountain Above -5.9638% over 22,600’ (4.28 mi)
Annual Average Daily Traffic (AADT) 1,609 (Year 2000)
Percent Trucks 10.1% (Year 2000)
Average Number of Accidents per Year 8.6 Total, 0.9 Tractor-Trailer
TER Usage Data Collected Between 03/09/1991 through 12/20/2000
Total Number of Uses 10
Total Number of Warranted Uses1 7
Conditions at Bottom of Grade Unknown
1 Warranted uses include brake failure, overheating and/or smoking brakes, failure to downshift properly and loss of air pressure in braking
mechanism.
Figure 2.2.17
State Route 77 SB TER – Typical Section
Truck Escape Ramp Study 2-26
Figure 2.2.18
State Route 77 SB TER – Plan and Profile (1 of 2)
Truck Escape Ramp Study 2-27
Figure 2.2.19
State Route 77 SB TER – Plan and Profile (2 of 2)
Truck Escape Ramp Study 2-28
Table 2.2.7
State Route 77 SB TER
State Route 77 SB TER, SR 77 MP 155.7
Variable Description
Mainline Station begin TER 3274+21.72
Type of TER Descending/Ascending Grade Arrester Bed
Exits Right side of roadway
Length 2760 feet total length
1690 feet exit ramp terminal
1070 feet of arrester bed including secondary retarder
Width Arrester bed width of 48 feet throughout.
Anchors Each side of ramp @ 150 foot intervals
Service Road 13.5 foot wide (not including anchors), paved, between TER
and roadway
Grade of TER Varies from –7.77% to +2.000%
Aggregate (if any) Unspecified
Depth of Aggregate Tapers from 6” at entry to 48” in 150’, maintains 48” for final
850 feet.
Aggregate Liner 4” CTB
“Last Chance” device 35’W x 29’D x 8’H aggregate mound (1 ½:1 slopes)
Entering Horizontal Curve Data
(Tangent sections not shown.)
Sta. 3422+27.48, R = 954.93’Lt, L = 791.53’ (14,800’ prior)
Sta. 3409+55.14, R = 2291.83’Lt, L = 780.00’ (13,500‘ prior)
Sta. 3397+79.93, R = 716.20’Rt, L = 943.09’ (12,400‘ prior)
Sta. 3388+49.77, R = 716.20’Lt, L = 807.85’ (11,400‘ prior)
Sta. 3379+91.88, R = 1432.40’Rt, L = 707.92’ (10,600‘ prior)
Sta. 3369+66.09, R = 2289.83’Lt, L = 1243.67’ (9,500‘ prior)
Sta. 3356+52.15, R = 1432.40’Lt, L = 700.21’ (8,200‘ prior)
Sta. 3348+23.73, R = 954.93’Rt, L = 934.17’ (7,400‘ prior)
Sta. 3337+60.11, R = 1432.40’Lt, L = 1093.27’ (6,300‘ prior)
Sta. 3329+30.84, R = 954.93’Rt, L = 525.40’ (5,500‘ prior)
Sta. 3320+37.13, R = 716.20’Rt, L = 971.18’ (4,600‘ prior)
Sta. 3310+61.13, R = 954.93’Lt, L = 940.83’ (3,600‘ prior)
Sta. 3284+75.37, R = 954.93’Lt, L = 906.62’ (1,100‘ prior)
Sta. 3274+21.72 – Truck Escape Ramp
Sta. 3265+58.40, R = 2291.83’Rt, L = 550.00’ (900‘ after)
Sta. 3256+82.58, R = 954.93’Lt, L = 997.78’ (1,700‘ after)
Sta. 3245+72.13, R = 2291.83’Rt, L = 452.78’ (2,800‘ after)
Sta. 3236+77.57, R = 954.93’Lt, L = 755.00’ (3,700‘ after)
Sta. 3227+32.76, R = 954.93’Rt, L = 1034.63’ (4,700‘ after)
Sta. 3206+28.54, R = 1909.86’Lt, L = 600.86’ (6,800‘ after)
Sta. 3195+58.54, R = 1432.40’Rt, L = 1336.81’ (7,900‘ after)
Sta. 3178+34.92, R = 1637.02’Lt, L = 2013.01’ (9,600‘ after)
Sta. 3143+06.54, R = 2864.79’Lt, L = 1401.94’ (13,100‘ after)
Sta. 3038+04.88, R = 5729.58’Rt, L = 2275.28’ (23,600‘ after)
Entering Vertical Geometry Sta. 3423+00, -5.0000% (14,900’ prior)
Sta. 3410+50, -0.3510% (13,600‘ prior)
Sta. 3400+50, -7.9850% (12,600‘ prior)
Sta. 3381+50, -3.4290% (10,700‘ prior)
Sta. 3373+50, -7.1000% (9,900‘ prior)
Sta. 3340+00, -4.0000% (6,600‘ prior)
Sta. 3333+50, +1.1667% (5,900‘ prior)
Sta. 3321+50, -8.0000% (4,700‘ prior)
Sta. 3309+50, +1.5440% (3,500‘ prior)
Sta. 3300+50, -6.6000% (2,600’ prior)
Truck Escape Ramp Study 2-29
Sta. 3274+21.72 – Truck Escape Ramp
Sta. 3264+00, -8.0000% (1,000‘ after)
Sta. 3233+00, -5.8571% (4,100‘ after)
Sta. 3226+00, -6.0000% (4,800‘ after)
Sta. 3208+00, -8.0000% (6,600‘ after)
Sta. 3175+00, -6.0000% (9,900‘ after)
Sta. 3154+50, -1.5135% (12,000’ after)
Sta. 3136+00, +2.5000% (13,800‘ after)
Sta. 3130+00, +0.7222% (14,400‘ after)
Sta. 3112+00, -3.3889% (16,200‘ after)
Sta. 3094+50, +0.8400% (18,000‘ after)
Sta. 3082+00, -2.8333% (19,200‘ after)
Sta. 3065+00, -3.8462% (20,900‘ after)
Sta. 3052+00, -7.0000% (22,200‘ after)
Sta. 3043+00, -2.5000% (23,100‘ after)
Sta. 3035+00, -3.6153% (23,900‘ after)
Sta. 3022+00, -3.0714%, (25,200‘ after)
Length of Mountain Grade Above Greater than 14,900’ (2.82 mi)
Length of Mountain Grade Below Greater than 25,200’ (4.77 mi)
Average Percent Grade of Mountain Above -5.1447% over 14,900’ (2.82 mi)
Annual Average Daily Traffic (AADT) 1,609 (Year 2000)
Percent Trucks 10.1% (Year 2000)
Average Number of Accidents per Year 8.6 Total, 0.9 Tractor-Trailer
TER Usage Data Collected Between 01/19/1990 through 08/04/1993
Total Number of Uses 26
Total Number of Warranted Uses1 11
Conditions at Bottom of Grade Unknown
1 Warranted uses include brake failure, overheating and/or smoking brakes, failure to downshift properly and loss of air pressure in braking
mechanism.
Figure 2.2.20
State Route 77 SB TER – Typical Section
Truck Escape Ramp Study 2-30
Figure 2.2.21
State Route 77 SB TER – Plan and Profile (1 of 2)
Truck Escape Ramp Study 2-31
Figure 2.2.22
State Route 77 SB TER – Plan and Profile (2 of 2)
Truck Escape Ramp Study 2-32
Table 2.2.8
US Route 60 WB TER
US Route 60 WB TER, US 60 MP 228
Variable Description
Mainline Station begin TER 97+31.82
Type of TER Descending/Ascending Grade Arrester Bed
Exits Right side of roadway
Length 1670 feet total length
680 feet exit ramp terminal
990 feet of arrester bed including secondary retarder
Width Arrester bed width of 48 feet throughout
Anchors Each side of ramp @ 150 foot intervals
Service Road 13.5 foot wide (not including anchors), paved, outside TER
and roadway
Grade of TER Varies from –5.707% to +2.000%
Aggregate (if any) Unspecified
Depth of Aggregate Tapers from 6” at entry to 48” in 150’, maintains 48” for final
840 feet.
Aggregate Liner 4” CTB
“Last Chance” device 48’W x 20’D x 6’H aggregate mound (1 ½:1 slopes)
Entering Horizontal Curve Data
(Tangent sections not shown.)
Not Available
Entering Vertical Geometry Not Available
Length of Mountain Grade Above Not Available
Length of Mountain Grade Below Not Available
Average Percent Grade of Mountain Above Not Available
Annual Average Daily Traffic (AADT) 6500 (Year 2000)
Percent Trucks 5.7% (Year 2000, 19.0% Year 1996)
Average Number of Accidents per Year 37.4 Total, 3.6 Tractor-Trailer
TER Usage Data Collected Between 03/04/1990 through 06/01/2001
Total Number of Uses 50
Total Number of Warranted Uses1 23
Conditions at Bottom of Grade Not Available
1 Warranted uses include brake failure, overheating and/or smoking brakes, failure to downshift properly and loss of air pressure in braking
mechanism.
Truck Escape Ramp Study 2-33
Figure 2.2.23
US Route 60 WB TER – Typical Section
Truck Escape Ramp Study 2-34
Figure 2.2.24
US Route 60 WB TER – Plan and Profile (1 of 2)
Truck Escape Ramp Study 2-35
Figure 2.2.25
US Route 60 WB TER – Plan and Profile (2 of 2)
Truck Escape Ramp Study 2-36
2.3 Photo Log Review
Photo logs supplying coverage of the areas in which truck escape ramps (TERs) currently exist
were reviewed at the Transportation Planning Division (TPD), Data Section. The ADOT Photo
Log provided information about advance signage, current TER conditions, and roadway
conditions in advance and after TERs as well as concurrence with as-built plans.
The following ADOT Photo Logs were reviewed:
Table 2.3.1
ADOT Photo Log Inventory
Truck Escape Ramp Location Photo Log #
Interstate Route 17 SB TER D_99611
Interstate Route 17 NB TER D_99907
US Route 89 WB TER D_99605
State Route 68 EB TER (Both) D_99703
State Route 77 SB TER (Both) D_99401
US Route 60 WB TER D_99403
2.4 Existing Truck Escape Ramp Data
Data on existing TERs was requested from the Intermodal Transportation Division (ITD), Traffic
HES Section. The Traffic HES Section maintains a record system, which contains data on
existing roadways, including TERs, within Arizona. Information including TER usage forms,
previous studies and policies are contained in this record system.
The Truck Escape Ramp Usage forms, typically completed by Department of Public Safety
(DPS) officers, identify information pertaining to the event. They typically include the date,
time, weather condition, type of vehicle, vehicle and cargo weight, speed of entry, length of
penetration into ramp, depth of penetration into gravel, condition of gravel bed, method of
removal and reason for ramp use. While some forms were not completely filled out, most
provided enough information to be useful for this study. The consistency with which these
reports were completed is questionable. For example, US Route 60 had 26 reported usages
(warranted and non-warranted) in 1990 compared with only 2 in 1992. It is probable that only a
portion of the actual usages become logged on the TER Usage forms, which somewhat
diminishes the reliability of the data.
The record system also contained Design Concept Reports and Project Assessment reports that
were completed for existing and previously proposed TERs within the State. The reports were
useful in determining what factors were considered in the determination of need and location, as
well as what design parameters were used.
Truck Escape Ramp Study 2-37
Additionally, ADOT prepared several technical reports for TERs in the 1980’s and 1990’s. The
reports focused on highway downgrades and truck escape ramp policies.
The record system also contained information about the US Route 60 TER, including as-built
plans, which were not on record with the ADOT Engineering Records. The plans were used to
partially complete the tables in Section 2.2 and to provide additional information about this
specific TER.
A majority of the information contained in the record, including previous policy and
recommendations, was used to develop and support recommendations presented in Chapter 3,
Documenting the State of the Practice.
2.5 Crash Data
Crash data supplying coverage of the areas in which TERs currently exist have been requested
from the Intermodal Transportation Division (ITD), Traffic Records Section (Jim Williams –
primary contact). In total, seven (7) locations were requested, representing the TERs tabulated in
Section 2.2 (US 60 WB MP 228.1 was not included).
Crash data was requested for the entire mountain downgrade on which the TER exists. If the
length of the downgrade was not known, the crash data was requested 4.0 miles prior and 4.0
miles after the location of the TER.
The crash was analyzed to determine if the existing TERs are reducing runaway truck accidents,
to assess whether the TERs are located in the appropriate spot, and what the relationship is
between percent grade, horizontal alignment and truck crashes.
2.6 Conclusions
Since the initial construction of truck escape ramps (TERs) began in Arizona in September 1982,
the Arizona Department of Transportation (ADOT) has eight TERs throughout the State, as
shown above in Table 2.1.1. While the specifics of each TER vary depending on the specific
site and terrain, several variables are constant throughout. Every TER constructed by ADOT is
of the arrester bed design, with a majority being on descending grade (non-gravity).
Additionally, every TER is equipped with wrecker anchors and a service road for removal and
maintenance purposes, along with a “Last Chance” device in the form of an aggregate mound.
An additional TER located along eastbound SR 80 has also been identified, although there are no
records relating it to an ADOT sponsored project. It is believed that a mining company in the
area constructed this TER.
A review of the information above found that almost all TERs were constructed on the lower half
of the downgrade. Slopes on downgrades with TERs ranged from –4.6% to –6.0%, sometimes
lengths exceeding 10½ miles. A comprehensive evaluation of TERs in Arizona, published
source in 1991 by ADOT reached the following conclusions:
Truck Escape Ramp Study 2-38
“All six (SR 77 SB MP 154.2 was not yet constructed) truck escape ramps in
Arizona have proven to be effective in stopping out-of-control vehicles. There
have been 70 reported uses of the ramps, which resulted in only three minor
injuries, not considering the Bullhead City ramp prior to modification. The 70
uses of the ramps probably prevented 70 accidents, which could have resulted in
costly property damage, serious injuries, and/or fatalities.”
“Truck escape ramps have proven to be useful countermeasures for reducing the
severity of runaway truck accidents in Arizona.”
A review of the as-built plans shows that design standards for the arrester bed are inconsistent.
For example, some widths are as great as 48 feet; others taper to as little as 26 feet. Additionally,
some have aggregate depths of 48 inches, while others only 24 inches. For this reason, the
development of better TER standards including the determination of need, site location and
design parameters may be beneficial. The primary goal of the TER’s on Arizona State highways
is that they provide an important function for out-of-control runaway vehicles at locations to
reduce the loss of life and property damage.
Truck Escape Ramp Study 3-1
Chapter 3
Documenting the State of the Practice
3.1 Research Process
The primary intent of this chapter is to research policies and procedures that have already been
established through Federal agencies, State agencies and technical societies and publications
with regard to truck escape ramps (TERs). Once this information is known, it will better allow
the Arizona Department of Transportation (ADOT) to understand the criteria for the evaluation
of need, location and design of TERs used throughout the country.
The research process was broken up into four separate areas of concentration; Internet material,
Federal agencies, State agencies and professional societies and publications. While it is
understood and widely accepted that there exist no clear standards for the location and design of
TERs, a review of current practice will allow for a more uniform set of guidelines for use within
the State.
Through the process, ADOT plans to compile the various criteria used to determine the need for
and location of TERs. Federal agencies will likely provide the best data for basic design, while
State agencies in mountainous regions will likely best provide information for the determination
of location. Society publications will provide technical analysis to support the design and
determination of location from the agencies above. Primary contacts were made with State
Departments of Transportation (DOTs) including Nevada (NDOT), Colorado (CDOT) and
California (Caltrans), and Federal agencies including the Federal Highway Administration
(FHWA).
3.2 Current Practices and Standards
3.2.1 Internet Research
For the purposes of this study, the internet was primarily used as a tool to find what information
is available on the subject matter, who has been producing work relevant to this project and
where it can be located. The internet provided key insights into which State DOTs had
guidelines on TERs, which society publications would best be searched for information and what
venders across the world were touting as the latest state-of-the-art technology.
As a means for providing guidance on which states have guidelines on TERs, the Internet proved
an excellent source, both in providing literature links as well as contacts, described in detail
under Section 3.2.4.
Several websites were found that linked the web search to various trucking related sites. It is
interesting to note that few of these sites provided any information regarding runaway trucks,
TERs, or the proper technique for downhill braking. In fact, the sites that did mention downhill
braking techniques refer to the old theory that has been rescinded, namely continuous application
of the brakes as opposed to intermittent application as the preferred method. Today there is
Truck Escape Ramp Study 3-2
almost unanimous agreement that the proper way to brake on a downgrade is to intermittently
apply all service brakes, reducing speed by 5 mph during each application. Virtually every
website that did mention runaway trucks stated brake failure as the primary cause.
Many vender websites are currently promoting vehicle-arresting barriers or dragnets in
combination with TERs as either a mechanism for additional safety or for use in situations were
topography does not permit the full design length to be achieved (See Figure 3.2.1). The
benefits to these systems include shorter distances than conventional gravel arrester bed ramps,
no susceptibility to weather and minimal maintenance. One website noted that by using a series
of nets, the dragnet system can withstand impacts of an 80,000 pound tractor-trailer at speeds up
to 80 mph with minimal damage to the vehicle and a reduction in the possibility of load shift and
jack knifing.
Figure 3.2.1
Dragnet Arresting Barriers (John Thomas, Inc.)
3.2.2 Federal Agencies
The two primary Federal agencies researched were the US Department of Transportation,
Federal Highway Administration (FHWA) and the American Association of State Highway
Transportation Officials (AASHTO).
Federal Highway Administration (FHWA)
The primary research reference published by FHWA is the Manual of Uniform Traffic Control
Devices (MUTCD). While the MUTCD does not provide guidance on the need, location and
design of TERs, it does provide guidance relative to signage for downgrades as well as TERs.
Specifically, the MUTCD states that Hill (W7-1) (See Figure 3.2.2) and Grade (W7-3) (See
Figure 3.2.3) signs should be used in advance of downgrades with the following conditions:
• 5% grade and more than 3,000 feet long
• 6% grade and more than 2,000 feet long
• 7% grade and more than 1,000 feet long
• 8% grade and more than 750 feet long
• 9% grade and more than 500 feet long
Truck Escape Ramp Study 3-3
The MUTCD also recommends installation of these signs on steeper grades or where accident
history or field observations indicate a need.
Figure 3.2.2
W7-1 Sign Series (MUTCD)
To compliment the Hill and Grade signage above, the MUTCD also recommends supplemental
plaques (W7-2 series) for emphasis or where special roadway characteristics exist. Where
appropriate, mileage plaques (W7-3a or W7-3b) should be used at intervals of one mile, to
provide additional information to vehicle operators (See Figure 3.2.3).
Where TERs exist or are being constructed, the MUTCD recommends the installation of W7-4
and W7-4a signage in advance of the ramp (See Figure 3.2.4). It notes that TERs are desirable
for the safe deceleration and stopping of runaway vehicles on long downgrades, where
installation of such ramps is practical. It further goes on to say that truck turnouts at the summit
of the grade and special trucker information signs may be helpful in situations were TERs or
steep downgrades are present.
Figure 3.2.3
W7-2 and W7-3 Sign Series (MUTCD)
W7-1
30”x30”
W7-1b
30”x30”
W7-3b
24”x18”
W7-3a
24”x18”
W7-3
24”x18”
W7-2b
24”x18”
Truck Escape Ramp Study 3-4
Figure 3.2.4
W7-4 Sign Series (MUTCD)
American Association of State Highway Transportation Officials (AASHTO)
The primary research reference published by AASHTO is A Policy on Geometric Design of
Highways and Streets (Green Book). The Green Book provides general information on TERs as
well as TER types and design considerations. The Green Book does state that specific guidelines
for the design of TERs are lacking at this time.
The Green Book states that where long downgrades exist or where topographic and location
controls require steep downgrades on new alignments, the installation of TERs at an appropriate
location is recommended to slow and stop an out-of-control vehicle away from mainline traffic.
An out-of-control vehicle is generally the result of loss of brakes either through overheating or
mechanical failure, or failure to downshift at the appropriate time.
There are three primary resistance forces that act on every vehicle to affect its speed: engine,
braking and tractive forces. For the purposes of TER design, engine and braking forces can be
ignored, as TERs should be designed for a worse case scenario where the vehicle is in neutral
and the braking system has failed. There are four subcategories under tractive resistance forces:
inertial, aerodynamic (air), rolling and gradient. Inertial and negative gradient resistance forces
act to maintain motion of the vehicle, while rolling, positive gradient and aerodynamic (air)
resistance forces act to retard the vehicles motion. The two main forces that TERs attempt to
control are rolling and gradient.
The Green Book recognizes three broad categories in which it classifies TERs: gravity, sandpile
and arrester bed. The Green Book notes that the gravity TER has no means of preventing the
runaway vehicle from rolling down the ramp and re-entering the mainline traffic. For this
reason, gravity ramps are the least desirable escape ramp. The remaining two categories are
further broken down into four basic types of TERs, which are currently in use: sandpile,
descending grade, horizontal grade and ascending grade.
Sandpile Composed of loose, dry sand, these ramps are usually less than 400 feet in
length. The influence of gravity is dependent on the grade of the sandpile
and the increase in rolling resistance is supplied by the loose sand.
W7-4
78”x48”
W7-4a
78”x60”
Truck Escape Ramp Study 3-5
Descending Grade These ramps can be rather lengthy, as the gravitational effect is not acting
to reduce the speed of the vehicle. The force of gravity acts in the
direction of the vehicle and the increase in rolling resistance is supplied by
an arresting bed composed of loose material.
Horizontal Grade These ramps can also be rather lengthy, for the same reason as the
descending grade. The force of gravity is zero and, similar to the
descending grade, arrestor beds are used.
Ascending Grade Use both the arresting bed and the effect of gravity, which in general
reduces the ramp length necessary to stop the vehicle. The loose material
acts to increase the rolling resistance while the force of gravity on the
upgrade acts opposite to the vehicle movement.
The Green Book goes into considerable detail with regard to design considerations. It notes that
the speed of out-of-control vehicles rarely exceeds 80 to 90 mph, which in turn should be the
minimum entering design speed for TERs. The ramp should be designed to safely stop the
largest vehicle that is expected to use the facility, which would generally be a WB-40 or WB-50.
Furthermore, the selection of the TER is usually based on accident experience, with the highest
attainable speed at that particular location being used as the minimum design speed for the ramp.
The Green Book states the following considerations for the design and construction of an
effective TER:
1. To safely stop an out-of-control vehicle, the length of the ramp must be sufficient to
dissipate the kinetic energy of the vehicle.
2. The width of the ramp should be sufficient to accommodate more than one vehicle. The
minimum width is 26 feet, with a desirable width between 30 to 40 feet.
3. The surface material used in the arrester bed should be clean, not easily compacted, and
have a high coefficient of rolling resistance. Aggregate should be rounded, single sized
and as free from fines as possible. A positive means of draining the arrester bed should
also be provided. Pea gravel is representative of the material used most frequently.
4. Arrester beds should be constructed with a minimum aggregate depth of 36 inches, with
42 inches recommended. To assist in decelerating the vehicle smoothly, the depth of the
bed should taper from three inches at the point of entry to full depth in the initial 100 to
200 feet.
5. The entrance to the TER must be designed so that a vehicle traveling at high speeds can
enter the ramp safely.
6. Signage of the ramp must be provided in advance with sufficient sight distance to allow
the driver of an out-of-control vehicle time to react. Illumination of the approach and
ramp is desirable.
AASHTO goes on to note that a surfaced service road, located adjacent to the ramp should be
provided to allow access for the wrecker and maintenance vehicles. The width of this lane should
be a minimum of 10 feet, with wrecker anchors spaced at 300-foot intervals.
The TER should exit to the right of the mainline, with an alignment tangent to the mainline or of
very flat curvature. TERs should be provided wherever a need is determined, but unnecessary
Truck Escape Ramp Study 3-6
ramps should be avoided, meaning if a TER is provided prior to a sharp horizontal curve, another
TER is not needed after the curve.
The Green Book states that the principal determinations as to the need for a TER should be the
safety of the other traffic on the roadway, the operator of the out-of-control vehicle, and the
residents along and at the bottom of the grade. To determine the distance required to bring an
out-of-control vehicle to a stop with consideration given to the rolling resistance and gradient
resistance, the following equation is recommended:
L = V2 / [30(R ± G)]
where: L = distance to stop (length of arrester bed), feet
V = entering velocity, mph
G = percent grade divided by 100; and
R = rolling resistance expressed as equivalent percent gradient divided
by 100 (See Table 3.2.1).
Table 3.2.1
Rolling Resistance Based on Material Type
Surfacing Material Rolling Resistance
(lb/1000ob GVW)
Equivalent Grade
(percent)1
Portland cement concrete 10 1.0
Asphalt concrete 12 1.2
Gravel, compacted 15 1.5
Earth, sandy, loose 37 3.7
Crushed aggregate, loose 50 5.0
Gravel, loose 100 10.0
Sand 150 15.0
Pea gravel 250 25.0
1Rolling Resistance expressed as equivalent gradient.
After each use, aggregate arrester beds should be smoothed and the aggregate loosened as
necessary. Additionally, the bedding material should be cleaned of contaminants and loosened
periodically to retain the retarding characteristics of the bedding material.
Where a full-length ramp is to be provided with full deceleration capability for the design speed,
a “last chance” device should be considered when the consequences of leaving the end of the
ramp are serious. Mounds of bedding material two to five feet high, with 1.5H:1V sideslopes,
have been used in several instances.
The Green Book provides the following figure (See Figure 3.2.5) as reference for a typical TER.
Truck Escape Ramp Study 3-7
Figure 3.2.5
Plan and Profile (AASHTO Figure 3-72)
Summary
Rather than providing specific guidelines for truck escape ramp (TER) need, location and design,
Federal agencies have published recommendations, and in some cases minimums to be
considered in TER development. Federal agencies recognize that on long downgrades, TERs
may be needed where out-of-control vehicles (primarily caused by brake failure associated with
overheating, mechanical failure or failure to downshift) could affect the safety of the general
public.
The agencies recognize four types of TERs: sandpile, descending grade, horizontal grade and
ascending grade, stating that which ever ramp is chosen, it should be sufficient in design to
accommodate a WB-40 to WB-50 vehicle traveling at speeds of up to 90 mph.
The agencies note that the length of the ramp should be calculated taking into account velocity,
percent grade and rolling resistance. A width of 26 feet is set as a minimum, with 30 to 40 feet
being desirable. If an arrester bed is used, the material should be clean, not easily compacted,
rounded and of one size with a high coefficient of friction. Pea gravel is sited as the most
commonly used material. The aggregate depth should be a minimum of 36 inches, tapering from
3 inches at entry to maximum depth within 100 to 200 feet. Signage is referred to in detail as a
necessary means of early warning to allow proper use of the TER.
Surfaced service roads are recommended adjacent to the TER for use by wreckers and
maintenance vehicles. The minimum width should be 10 feet, with anchors spaced at 150 to
300-foot intervals. After each use the aggregate should be smoothed and loosened. “Last
chance” devices should be considered in locations where the design length is not met or the
consequences of leaving the ramp are serious.
Truck Escape Ramp Study 3-8
3.2.3 Arizona Department of Transportation
While the Arizona Department of Transportation’s (ADOT’s) Roadway Design Guidelines
(1996) does not contain specific information on the determination of need, location and design
standards for truck escape ramps (TERs), it does provide minimal guidance.
The guidelines indicate that there are two primary types of TERs: gravel arrester bed and gravity
ramps. The guidelines also note that the gravity ramp is preferred over the arrester bed ramp due
to its construction and maintenance costs, citing that Arizona does not have an ample supply of
rounded gravel necessary for arrester bed construction.
ADOT states that the primary indicator of a runaway truck problem is a history of runaway truck
accidents along sustained downgrades, usually near a horizontal curve. Hot and/or smoking
brakes should be used as a secondary indicator. The graph below (See Figure 3.2.6) should be
used to assess the need for a TER.
Figure 3.2.6
Determination of Need (ADOT Figure 209.4A)
The Roadway Design Guidelines state that experience has shown that ramps located three to four
miles from the summit of the downgrade will intercept up to 80 percent of the runaway vehicles.
The guidelines offer little with respect to design standards, but does specify that the ramp should
not be located on a curve, should be equipped with wrecker anchors spaced at intervals of 150
feet and the aggregate in the arrester bed should taper from an initial depth of six inches to a final
depth of 48 inches within the first 150 feet. Additionally, the guidelines state that both arrester
beds and gravity ramps should have service roads along the entire length of the ramp (See
Figure 3.2.7).
Truck Escape Ramp Study 3-9
The length of the escape ramp will vary depending on the specifics of the site, but should be
calculated using the following equation:
L = V2 / (30 (R ± G))
where: L = arrester bed length, feet
V = entering speed in mph, typically 90 mph
R = coefficient of rolling resistance (0.25 for pea gravel)
G = algebraic grade in percent
Figure 3.2.7
Plan and Typical Section (ADOT Figure 208.4B)
ADOT notes that brake check areas should be provided both as interim solutions while TER
construction is being considered as well as after construction, to provide information pertinent to
the downgrade, horizontal alignment and location of the TER.
Aside from the ADOT Roadway Design Guidelines, ADOT has also authored a number of
technical reports, which chronicle the development of TER standards in Arizona and provide
Truck Escape Ramp Study 3-10
more specific guidelines and policies regarding TER need, location and design. The following
provides a summary of these reports:
Emergency Truck Escape Ramp on US 60 East of Superior, January 1980
This technical report presents the proposal, including preliminary geometrics and signing, for a
truck escape ramp (TER) on US 60 east of Superior and immediately west of the Queen Creek
Tunnel. The proposal notes that due to topography, the TER was designed as a gravel arrester
bed.
The location of the TER was determined by analyzing topographical features, existing roadway
alignment and historical accident experience. The TER was placed in advance of geometrically
restrictive areas further downgrade. The TER also takes advantage of a short tangent section of
roadway.
The TER was designed with an entering design speed of 80 mph capable of accommodating a
WB-50 vehicle. The TER has a zero percent grade and an arrester bed length of 950 feet, with
an additional 350 feet on the exit ramp terminal. The report discusses the minimum sight
distance required for the design speed and percent grade of the downgrade, indicating that cut
sections will be required to achieve minimum sight distances.
The arrester bed material was designed for ¼ to ⅜ inch diameter pea gravel. Other materials,
including blow sand, cinders and fly ash were considered for the arrester bed material, but were
found to create excessive internal friction and thus would not be suitable arrester materials. The
report notes that the arrester bed will need to be re-leveled and loosened after each use and that
the gravel be loosened periodically to maintain design drainage and energy absorption
characteristics. It states that the pea gravel may need to be cleaned or replaced over time.
For additional safety, the report calls for a sand berm at the end of the ramp for vehicles that may
have overrun the ramp. Additionally, due to the large, steep fill sections, tri-beam guardrail
should be installed on both sides of the TER to prevent vehicles from sliding down the fill
slopes.
The report utilizes a different means of calculating the required length of the arrester bed, taking
into account the aspects of physical mechanics. The end result is similar to that of the equation
specified in the Roadway Design Guidelines.
Final Design Concept Report, Bitter Springs Jct. US 89 & US 89A, Emergency Truck Escape
Ramp, February 1982
The Final Design Concept Report (DCR) for the US 89A TER was prepared primarily due to
accident history and the potential for runaway vehicles to not be able to stop, as required at the
time, at the intersection of US 89 and US 89A. At the time of this report, US 89 created a Tee-intersection
with US 89A, at which, US 89 was required to stop. (Since then, the intersection has
been reconfigured, allowing US 89 the through movement and requiring southbound US 89A to
stop.) Over a 3½-year period, 51 accidents were reported. One of these 51, and six others that
were not reported, involved truck combinations that failed to stop at the intersection.
Truck Escape Ramp Study 3-11
The TER was designed to accommodate a design speed of 85 mph and is located on a tangent
section. The length of the TER is to be approximately 1700 feet (total length). A service road
was constructed away from the through roadway for wreckers to assist embedded trucks. The
end of the TER reconnected with the mainline movement of US 89A. Wrecker anchors were
planned on both sides of the ramp every 300 feet. Advance signing will notify truckers and other
roadway traffic of the approaching TER.
Design Concept Report, I-17 NB Truck Escape Ramp, December 1984
The Final Design Concept Report (DCR) for the I-17 northbound TER considered providing a
truck escape ramp near milepost 283 to increase the efficiency and safety of the existing
highway. Located along the rim of Copper Canyon, the DCR called for a TER to be constructed
in the median of the interstate.
The TER design consisted of an aggregate depth of 24 inches. Pea gravel was used as the
arresting material. A paved service road was used adjacent to the TER to allow wreckers and
maintenance vehicles easy access. Wrecker anchors were spaced along the service road at 300-
foot intervals. Prior to the downgrade, a brake check area some 250 feet long and 45 feet wide
was constructed at the summit (MP 280.4). Signing was provided for both the brake check area
and TER.
Aside from accident history, three other factors were considered when determining the proper
location of the TER, including calculations of the physics of runaway vehicles, interview with
the Department of Public Safety (DPS) and interview with truck drivers at the site.
Calculations involving the physics of runaway vehicles yielded speed-distance diagrams from
which the overturning and sliding velocities of an 80,000-pound truck were calculated.
Interviews with truck drivers at the existing brake check area indicated that a TER on the left
side of the mainline is acceptable so long as high traffic volumes do not exist.
The TER consists of both descending and ascending grades, ranging from –4.58% to +2.00%. A
gravel attenuator berm is provided at the end of the arrester bed, composed of pea gravel. The
width of the arrester bed tapers from 40 feet at the point of entry to 26 feet in the first 400 feet.
Truck Emergency Escape Ramps, August 1985
Prior to the development of this policy report, two accidents occurred on Arizona highways that
involved runaway trucks. The two accidents resulted in a total of 10 fatalities, prompting more
detailed investigations into truck escape ramps (TERs). This policy report includes discussion
of what TERs are, where they should be located, studies that have been previously completed
and where TERs exist or are planned.
The policy report describes TERs as areas to the side of a highway that provide a means to slow
and stop an out-of-control vehicle. There are four types of TERs considered in this report,
including sandpile, ascending grade, horizontal grade and descending grade. The main forces
that act to slow the out-of-control vehicle are gravity (sandpile and ascending grade) and rolling
resistance (all four).
Truck Escape Ramp Study 3-12
The policy report notes that there are no nationally adopted guidelines for the development of
TERs, and that States are largely on their own to develop standards specific to their geography.
The following thirteen guidelines were developed for TERs in Arizona:
1. Establish a brake check area immediately preceding the crest of the downgrade.
2. Locate the ramp in an area where a runaway truck can exit the roadway on a tangent and
desirably provide a positive grade for the escape ramp.
3. If a location cannot be found with a positive grade, the negative grade should be
decreased as much as possible.
4. Access to the ramp must be well marked in accordance with the MUTCD and should be
designed for an entrance speed of 90 mph.
5. Pave the throat of the ramp plus sufficient distance to allow all wheels to leave the
mainline roadway pavement prior to entering the arrester bed.
6. The arrester bed should be constructed with only round gravel ¼ inch to ⅜ inch in
diameter.
7. Adequate drainage must be provided to prevent ponding of water and minimize freezing
during periods of cold weather.
8. To insure that a vehicle utilizing the ramp will not be stopped abruptly, the depth of the
arrester bed should vary from 12 inches to 30 inches in the first 400 feet.
9. A barrier with a sand barrel energy attenuator should be placed at the end of the ramp.
10. The ramp should be 40 feet wide at the entrance point and narrow to 20 feet in the first
500 feet.
11. A service road should be constructed adjacent to the arrester bed and should be surfaced
so that wreckers and maintenance vehicles may use it without becoming stuck. Wrecker
anchors should be installed adjacent to the service road at a spacing of 300 feet.
12. The edge of the arrester bed shall be delineated with red delineators.
13. The following assumptions shall be used in determining the length of the ramp:
a. Gross axle weight = 32,000 pounds
b. Entrance speed = 90 mph
c. Final speed = 0 mph
d. Coefficient of rolling resistance = 0.25
e. Grade = actual grade of ramp
The policy report states that ADOT follows AASHTO’s recommendation that the need for a
truck escape ramp (TER) is typically determined by analysis of accident data. Additionally, the
report notes that most of the accidents involving runaway vehicles occur on grades exceeding
five percent over a distance exceeding two miles.
The policy report noted that at the time of publication, there were only three truck escape ramps
(TERs) in the state, with an additional one under construction. Additionally, there are over 100
locations that have grade warning signs and 16 locations where there are pullout areas for brake
checks.
The report concludes that ADOT has done a good job of analyzing accident data and installing
TERs, grade warning signs and brake check areas where needed. It recommends that the study
be updated to reflect current accident data. An inventory of locations where grades are five
Truck Escape Ramp Study 3-13
percent of more for a distance greater than two miles should also be included. If locations exist
with high accident rates in these areas, TER evaluations should be considered.
Assessment of Heavy Vehicle Accidents on Highway Downgrades, October 1985
This report notes that on long steep downgrades, the possibility of runaway trucks due to brake
failure, driver error, mechanical failure or some combination of the above, it a problem on
Arizona highways. The report notes that in the absence of national standards for TERs, the
thirteen design guidelines presented in Truck Emergency Escape Ramps, August 1985 (above)
should be used.
This report goes further than the previous in laying out a manner by which to determine whether
or not a truck escape ramp (TER) is economically warranted. The methodology presented in this
report utilizes a net present worth approach. The present worth of benefits assigns a dollar
amount to the reduction in accident rates attributed to the TER. The present worth of the costs
consists of construction costs plus periodic maintenance costs. Calculations resulting in the net
present worth being greater than zero are considered economically desirable, with the larger the
number representing the more desirable the improvement. The following steps should be taken:
1. Collect geometric design, environmental and accident data.
2. Identify feasible escape facility design types.
3. Calculate preliminary construction and maintenance costs for each feasible design type
identified in Step #2.
4. Calculate present worth of costs for each escape ramp type identified in Step #2.
5. Calculate present worth of accident costs (benefits) for each downgrade over the life of
the proposed improvement.
6. Compare the present worth of costs (PWC) with the present worth of benefits (PWB). If
PWC is greater than PWB, go to Step #11. If PWC is not greater than PWB then the
downgrade should receive further evaluation.
7. Identify and select potential ramp locations using either (or both) method: accident
diagram plotted for the downgrade, cumulative degree of curvature plot for the
downgrade.
8. Select escape ramp design type for each potential ramp location and calculate present
worth of costs for each ramp location.
9. Calculate reduction in vehicle accident rate and present worth of accident costs (benefits)
for each potential site.
10. Compare present worth of costs to benefits. If the net present benefit is positive the site
is selected and recommended for construction of an escape ramp. If more than one site is
positive, select the site with the greatest net present worth. If the net present benefits are
negative than go to Step #11.
11. Check for special conditions such as land use development. If still not warranted, then
examine alternative measures such as improved warning signs, brake check areas or
alternative truck routing.
The report notes that ADOT has limited experience with costs associated with TERs. Generally
speaking, descending grade ramps will have the highest costs, some as high as $1.3M compared
to the $0.8M for an ascending grade TER. Typical construction materials for TERs are as
follows:
Truck Escape Ramp Study 3-14
• Bituminous or Portland cement concrete pavement transition from through lanes to
escape ramp
• Aggregate base course for transition pavement
• Shoulders for transition roadway
• Aggregate for escape ramp service road
• Pea gravel for arrester bed
• Wrecker anchors
• Reinforced concrete pipe for drainage
• Drainage inlets
• Fencing
• Clearing and grubbing of site
• Unclassified excavation
• Guardrail
• Signing
The report notes that after a period of time, the pea gravel arrester bed may become
contaminated. At some point, it may become necessary to completely replace or clean the pea
gravel.
Truck Escape Ramp Policy, January 1987
The Truck Escape Ramp Policy, written by the ADOT Traffic Engineering Section, provides the
most complete policy within the State on the implementation and design of truck escape ramps
(TERs) to date. The policy report not only discusses the determination of need and location, but
also the design standards that should be used for the different types of truck escape ramps
(TERs).
Three types of TERs are recognized by this report: gravity ramps, sand piles and gravel arrester
beds. The report notes that based on previous national empirical studies and the ADOT
experience with three gravel arrester bed TERs, ADOT has established the gravel arrester bed as
its standards design for TERs. This is primarily because gravel arrester beds are the most
flexible of the various types of TERs, they are free of topographical limitations, they offer larger
drag forces than sandpiles and function effectively over a wide range of speeds.
The study notes that the primary indicator of need is the number of accidents that occur in
conjunction with long sustained downgrades, usually near a horizontal curve. A secondary
indicator of the need for a TER is the number of vehicles with hot and/or smoking brakes.
Additionally, information regarding the need for a TER can also be pursued from professional
truck drivers, wrecker operators, Department of Public Safety (DPS) Officers and by inspection
of accident records.
When new facilities are in question, and there is no previous data to analyze, the graph below
can be used (See Figure 3.2.8). Developed by Caltrans, the graph plots the relationship between
percent downgrade and length of downgrade. If the new roadway combination yields a point to
the right of the curve, further consideration should be given to a TER during initial design. The
curve assumes that vehicles arrive at the summit with brakes at normal operating temperatures.
If it is likely that vehicles will arrive at the summit with hot brakes, the curve should be adjusted
Truck Escape Ramp Study 3-15
to the left accordingly. Additional factors to consider are the volume and nature of the truck
traffic.
Figure 3.2.8
Relationship between Percent and Miles of Downgrade (ADOT)
Once the need for the TER has been determined, the next step is to determine the proper
location. The location of TERs is largely controlled by topography. Typically, an escape ramp
should only be considered on the lower half of a downgrade, and if at all possible, should be
located on a tangent and not on a curve. TERs should normally be located on the right side of
the roadway, although left side exits are permitted on divided highways.
In general, the approach to the ramp should be as simple as possible. The approach to the gravel
arrester bed should be squared off so that all wheels on an axle enter the arrester bed at the same
time. Whenever possible, sag and crest curves on the approach should be avoided, as this may
lead to driver confusion. If possible, an auxiliary lane should be provided. When considered, the
auxiliary lane should be a minimum of 1,000 feet long (See Figure 3.2.9).
Truck Escape Ramp Study 3-16
Figure 3.2.9
Desired Alignment for Truck Escape Ramp (ADOT)
The TER alignment should be on one continuous tangent. If an auxiliary lane is not used, the
departure angle between the through movement and the TER should be as flat as possible, and
capable of safely accommodating a vehicle traveling at the design speed (90 mph).
The policy notes that the arrester bed width of 26 feet generally will provide adequate
maneuvering room. It also notes that this width will theoretically accommodate a second vehicle
prior to the first being removed. A paved service road, normally on the same side of the TER as
the highway, should be constructed with a minimum width of 13.5 feet. Whenever possible, it is
desirable to have the service road return to the through movement. Along the edge of the service
road and arrester bed, wrecker anchors should be spaced at 150-foot intervals along both sides of
the arrester bed (See Figure 3.2.10). Additionally, anchors should also be placed in advance of
the gravel bed approximately 150 feet.
Truck Escape Ramp Study 3-17
Figure 3.2.10
Wrecker Anchor Detail (ADOT)
The primary theory behind the gravel arrester bed is that the vehicle will sink into the gravel,
slowly bringing the out-of-control vehicle to a safe stop. To do this, the material must have a
low bearing capacity and not be easily compacted; characteristics usually found in single-sized,
well-rounded stream gravel. The aggregate used in the arrester bed shall be in compliance with
ADOT Materials Specifications as shown in Table 3.2.2 below.
Fine materials are sited as one of the principal contaminants of arrester beds. Contamination can
come from four main sources; existing ground, surface, vehicles and the gravel itself. Paving the
bottom and sides of the arrester bed basin can control ground contamination. Contamination
brought by the surface can be minimized by an adequate drainage system, providing good
roadway drainage as well as arrester bed drainage. Contamination caused by vehicles entering
the arrester bed is difficult to control, as they are usually unpreventable. And using high quality
gravel can minimize contamination from the aggregate itself.
To minimize the need to remove and replace or wash the gravel, the policy states that it is
desirable that the arrested bed be of sufficient depth to allow normal contamination, but still
maintain the ability to retard and stop an out-of-control vehicle. Arrester beds shall gradually
increase from an initial depth of six inches to a maximum depth of 48 inches in the first 150 feet.
The surface of the arrester bed aggregate should be as smooth as possible with no humps or
hollows (See Table 3.2.2).
Truck Escape Ramp Study 3-18
Table 3.2.2
Materials Specification (ADOT)
Specification for Arrester Bed Aggregate
Description: The work shall include furnishing and placing arrester bed aggregate.
Materials: Aggregate for the arrester bed and secondary retarder material shall be
clean, uncrushed, inert stone or gravel composed of naturally rounded
screened particles free from lumps or balls of clay, calcareous or clay
coating, caliche, synthetic materials, organic matter or other deleterious
substances.
The arrester bed and secondary retarder aggregate shall conform to the following
requirements:
The gravel shall be washed.
Gradation – (ARIZ. 201b, Section 12(3))
Sieve Size 1 Percent Passing
1 inch 100
½ inch 0 – 5.0
No. 200 0 – 2.0
Abrasion – (AASHTO T 96) 500 Rev., Maximum 35%
Bulk Specific Gravity – (ARIZ 211b) Range 2.30 to 2.85
Water Absorption – (ARIZ 211b) 4% Maximum
Fractured Faces – (ARIZ 212) 10% Maximum
Flakiness Index (ARIZ 233b*) 7% Maximum
*ARIZ 233b shall be modified as follows:
1. Paragraph 2 (c) add 1” sieve.
2. Table I: is revised to read:
Table I
Sieve Size
Passing Retained Weight, G
1 inch ¾ inch 1,200
¾ inch ½ inch 1,000
½ inch ⅜ inch 700
⅜ inch ¼ inch 300
¼ inch No. 4 200
No. 4 No. 8 100
3. Table II: is revised to read:
Table II
Size of Material
Passing Retained Slot Width, G
1 inch ¾ inch 0.525
¾ inch ½ inch 0.375
½ inch ⅜ inch 0.263
⅜ inch ¼ inch 0.184
¼ inch No. 4 0.131
No. 4 No. 8 0.084
Truck Escape Ramp Study 3-19
The contractor is advised that special processing methods, including the use of slotted
screens, may be necessary during production of this material in order to meet the
gradation and flakiness index requirements. Potential sources should be thoroughly
examined to assure that materials meet all requirements. No changes to these
requirements will be authorized.
The policy states that roadway runoff should be channeled away from the arrester bed and not
allowed to flow into the aggregate. It notes that water that does enter the arrester bed needs to be
drained as quickly as possible. French drains, perforated pipes, slotted drains and sloping of the
prepared base are typical methods used to properly drain arrester beds.
The specific length of the truck escape ramp (TER) will vary depending on the TER type,
material used, entering speed, etc. In terms of length, the ideal TER would be on an ascending or
positive grade. The more positive the grade, the shorter the ramp needs to be since additional
gravitational forces would be working in the ramps favor. Since many parameters are unknown,
the following equation is used to provide for a conservative ramp length:
L = V2 / [30 (R ± G)]
where: L = Distance to stop in feet (arrester bed length)
V = Entering speed in miles per hour
G = actual percent grade divided by 100
R = 0.25 assumed drag coefficient of friction
A 90 mph entry speed is the minimum that shall be used for design.
The policy identifies several aspects of traffic control as being key components of TER design.
The policy states that the edge of the arrester bed shall be delineated with red delineators, spaced
at 50-foot intervals, as shown in ADOT Standard Drawing 4-M-1.25 (See Figure 3.2.11). It also
notes that while advance signing is usually site specific, the typical advance signing is presented
in ADOT Standard Drawing 4-S-1.16 (See Figure 3.2.12) and is essential in notifying the driver
of an out-of-control vehicle about the TER ahead. Similarly, striping is usually site specific, but
typical pavement markings for TERs are included in ADOT Standard Drawing 4-M-1.25.
After each use, the policy notes that the arrester bed should be smoothed. It is essential that the
arrester bed be maintained as soon as possible following the extraction of a vehicle to provide
optimum conditions for the next use. Desirably this would happen within 24 hours. The gravel
will need to be loosened from time to time to maintain the optimum properties for which it was
selected. Ideally the equipment being used to maintain the TER would perform all or most of the
work from the service road, and not in the gravel itself.
The final point made by the policy is that a brake check area should be provided prior to the
summit of a downgrade on which there is a TER. The safety pullout should be designed and
signed in accordance with ADOT Standard Drawing 4-S-1.06 (See Figure 3.2.13).
Truck Escape Ramp Study 3-20
Figure 3.2.11
Standard Drawing 4-M-1.25 (ADOT)
Figure 3.2.12
Standard Drawing 4-S-1.16 (ADOT)
Truck Escape Ramp Study 3-21
Figure 3.2.13
Standard Drawing 4-S-1.06 (ADOT)
Truck Escape Ramps in Arizona – A Comprehensive Evaluation, December 1991
The Comprehensive Evaluation prepared by ADOT in 1991 summarizes the characteristics of the
six existing (1991) truck escape ramps (TERs) and evaluates the ramps’ abilities to reduce the
number of accidents associated with defective or overheated brakes. The study notes that out-of-control
vehicles are typically the result of a driver losing control of their vehicle due to a loss of
brakes either through brake overheating, mechanical failure, or failure to downshift at the
appropriate time.
The report notes three types of truck escape ramps (TERs); gravity ramps, sand and gravel
arrester beds, and a combination of both. The six TERs constructed between 1982 and 1990 by
the Arizona Department of Transportation include I-17 NB (MP 283), I-17 SB (MP 300), US 60
WB (MP 228), SR 68 WB (MP 1), SR 77 SB (MP 155) and US 89 SB (MP 524). These TERs
were considered in this evaluation.
The evaluation found that three of the TERs in Arizona are of the arrester bed type, and the other
three are a combination of arrester bed and gravity. Additionally, of the 70 reported uses of the
TERs, only three minor injuries were reported. A majority of the uses of the TERs have been by
tractor-trailers. Other occurrences have included tanker trucks, smaller commercial vehicles, a
motor home and passenger cars pulling trailers; all of which were out-of-control. The ramps
were effective in bringing these vehicles to a safe stop.
Furthermore, four of the downgrades have shown a reduction in the number of accidents
involving out-of-control vehicles after completion of the TERs. The signing for all six TERs
Truck Escape Ramp Study 3-22
either meets or exceeds the minimum presented in the MUTCD, Section 2C-26 and in the ADOT
Truck Escape Ramp Policy (1987).
The evaluation concluded by stating that the truck escape ramps (TERs) have proven to be a
useful countermeasure for reducing the severity of runaway truck accidents in Arizona.
Value Engineering Study, SR 177 Truck Escape Ramp, April 1994
In July 1993, a field review meeting was convened with the goal of developing a Project
Assessment (PA) with feasibility and cost estimates for a truck escape ramp (TER) along State
Route 177 near Ray Summit. A five-year accident history ending in December 1992 showed a
total of 30 accidents occurred, 19 of which were “run off road”. The more severe accidents
occurred to the south of Ray Summit near milepost 159.6. The downgrade to the south of Ray
Summit is at 10% for over one mile, culminating in a pair of severe reverse curves.
Three possible ramp locations were discussed. All three would require deep fills and steep side
slopes, with one of the alternatives requiring the purchase of a residence.
The meeting concluded with a request for sketches and preliminary cost estimates for the three
alternative locations discussed. It was also agreed that Ray Mine Complex, ASARCO would be
contacted for their input of the need for and preferred location of an escape ramp.
In August 1993, a follow-up memorandum was transmitted to individuals who attended the July
1993 field review meeting to provide additional information as concluded prior. The memo
identified borrow as the most significant expense for each of the alternatives considered.
The alternatives included:
Alternative 1 - Arrester bed with a length of 900 feet on level grade and
total length of 1100 feet. Requires approximately 949,000 cubic
yards of fill, with an approximate cost of $3,406,600.
Alternative 2 - Arrester bed with a length of 1200 feet on –5% grade and a
total length of 2000 feet. Requires approximately 1,131,600 cubic
yards of fill, with an approximate cost of $4,178,800.
Alternative 3 - Total length of 1300 feet with compound grade beginning
with –10% which decreases to –5% in 150 feet. Requires
approximately 411,400 cubic yards of fill with an approximate cost
of $2,545,900.
Alternatives 1 and 2 both depart just prior to the first curve, while Alternative 3 departs from the
tangent section between the first and second curve.
ASARCO – Ray Mine Complex was contacted regarding the need for and location of TERs
along SR 177. They did feel there was a need for a southbound ramp, and felt it would best be
located between the two curves near milepost 159.6 (similar to Alternative 3). They noted that
hauling firms typically have high turnover rates, and it is not unusual to have drivers who are
unfamiliar with the roadway. They also noted that most drivers would attempt to successfully
negotiate the first curve.
Truck Escape Ramp Study 3-23
In September 1993, traffic accidents were analyzed in detail for the 10-year period between
January 1982 and July 1993. Five accidents were reported on the four-mile grade from Ray
Summit, which involved southbound vehicles with defective brakes. The analysis concluded that
based on traffic accident data only, a truck escape ramp may be most beneficial to southbound
vehicles just prior to the second curve.
Later in September 1993, following the traffic accident analysis, another memorandum was
distributed providing a recommendation for which alternative to pursue. The memo noted that
the segment of SR 177 between milepost 161 and milepost 159 is perceived by ADOT engineers
as a high hazard area requiring remedial action, for which a Project Assessment was initiated to
develop a truck escape ramp (TER).
In total, three alternatives were considered at a field review, with the critical issue being whether
the TER should be before or after the first curve. To determine this point, the traffic accident
analysis was reviewed. Four of the five accidents involved trucks traveling at high speed and/or
without the use of their brakes. All four of these trucks were able to negotiate the first curve.
The range of vehicle speeds along the downgrade varied depending on start conditions and the
effect of the braking mechanisms, ranging from 20 mph for a truck with fully functioning brakes
to 95 mph for trucks with no retarding forces. Analysis indicates that trucks losing their brakes
half way down the downgrade would be entering the first curve at speeds around 65 mph.
Based on the accident analysis and the speed calculations, it was recommended that Alternative
3, between the two curves, be developed.
In October 1993 another field review meeting occurred to develop a consensus recommendation
on the location of the proposed TER. It was agreed that Alternative 3 would be pursued, with
some sort of barrier to be included to prevent wreckers and pedestrians from accidentally going
over the edge of the embankment.
In December 1993 the Initial Project Assessment (PA) was prepared. The initial focus of the PA
was to determine the optimum location for the TER. The PA notes that the downgrade to the
north of Ray Summit is at –10% but for only ½ mile, followed by flatter grades and mild
horizontal curves. Thus, there does not appear to be a need for a TER in this location. The
roadway south of Ray Summit also has a –10% downgrade, but for over 1 mile, followed by a
pair of reverse curves. Discussion with local ADOT and mining staff indicate that the area
between the two curves would be the ideal location for a TER.
Alternative 3 (from above) was selected as the recommended option because it is more likely to
be used, as determined from the accident analysis. Additionally, Alternative 3 better complies
with the standards presented in the ADOT Truck Escape Ramp Policy in terms of geometric
design. Preliminary plans show the ramp will have an aggregate depth of 12 inches at the point
of entry and taper down to 48 inches in the first 150 feet. The depth will remain at 48 inches
throughout. The grade of the arrester bed will transition from –10% to –5% after the first 500
feet.
Truck Escape Ramp Study 3-24
In April 1994 a Value Engineering Study was undertaken. The study recognized the following:
• Both horizontal and vertical geometrics in the study area are severe.
• The TER is warranted on ADT (truck) and alignment criteria, but not on number of
accidents.
• The project has a high cost in comparison to other ramps.
• Earthwork accounted for 77% of the project cost.
The study also brainstormed ideas for reducing the cost of the ramp, as stated below:
• Re-evaluate ramp design speed.
• Provide better drag coefficient for arrester material.
• Limit the arrester bed length to 600 feet, providing crash barrels at the end.
• Don’t provide adequate width for the trucks (26 feet maximum).
• Seek approval for lower design speed.
• Use geotextile in place of cement treated base.
• Reduce arrester bed depth to 36 inches from 48 inches.
The study concludes with the recommendation that the PA be put on hold pending determination
of the project’s priority based on cost.
Following the Value Engineering Study, in April 1994 the project was put on hold, based on the
initial project assessment scope and project cost.
Candidate Location for an Operations and Safety Evaluation, US 60 MP 289.00 to MP 293.00,
Salt River Canyon, November 1998
At the request of the Globe District, the Candidate Location for an Operations and Safety
Evaluation (CLOSE Report) was conducted on US 60 through the Salt River Canyon. The report
was targeted with three specific items for consideration: possible guardrail improvements,
installation of a westbound passing lane and installation of an eastbound truck escape ramp
(TER).
The report found that during a three-year period from May 1995 through April 1998 there were a
total of 44 reported accidents on this section of highway. In total, 27 of the accidents involved
vehicles that ran off the road, 15 of which were trucks. All but two of these accidents occurred
north of the location that was initially considered for the TER.
The traffic accident data did not support the need for a TER at MP 290.80 as initially considered,
but did support installation of a TER at MP 291.60. In addition to the TER, it was concluded
that improved warning signage should be installed to encourage operators to use lower gears. A
majority of the truck related accidents involved vehicles entering restrictive geometry in too high
a gear. The report noted that the smell of hot brakes was ever-present during a field review at
this location.
The initial location for the TER at MP 290.80 was rejected in favor of a TER located at MP
291.60. The primary reasons for this were:
Truck Escape Ramp Study 3-25
1. Most of the truck related accidents occurred down the hill from the initially considered
location.
2. The presence of several curves on the approach, which would limit sight distance to the
ramp entrance.
The list below presents the factors for and against the installation of the TER at MP 290.8.
Support For:
• Most of the construction would take place off the roadway, minimizing traffic
control and delays.
Support Against:
• The TER would be located too near the top of the downgrade.
• The TER would form a prolongation of the approach to the curve.
• The approach to the TER location is not on a tangent.
• There would be no way to provide a return for the service road.
• The proposed TER would cross two or three major drainages.
• New right-of-way would have to be acquired.
• There is no room to install an extended entrance to the TER, or an auxiliary lane
on the approach.
The list below presents the factors for and against the installation of the TER at MP 291.6.
Support For:
• This location is just before the curve where the majority of truck run-off-road
accidents have occurred.
• The TER would be located on a reasonably tangent section of roadway.
• Drainage modifications would probably be limited to extension of three culverts.
• This location would allow installation of a service road return.
• Little to no new right-of-way would have to be acquired.
Support Against:
• Most of the construction would take place in or immediately adjacent to the
roadway.
• There is no room to install an extended entrance to the TER, or an auxiliary lane
on the approach.
The report completes a benefit/cost ratio economic analysis to determine if the annual benefit in
terms of accidents prevented outweighs the costs of constructing and maintaining the TER for its
life (20 years). The report notes that the economic analysis of a TER is not as straightforward as
most highway improvements. This is mainly because most highway improvements function
without deliberate action taken on the part of the driver. TERs are different in that not only does
the driver need to recognize that there is a problem, but they must also recognize the risk
associated with not using the TER and take action to use the improvement.
The next steps are to determine accident reduction factors associated with the proposed TER and
associated costs of each type of accident. Since it was perceived that a tractor-trailer would
cause a greater deal of damage than passenger vehicles (the majority of accidents that make up
Truck Escape Ramp Study 3-26
the established accident costs), the values were all raised $48,000, with the exception of “Fatal”,
which remained unchanged.
Once the reduction factors and associated costs have been determined, an estimated construction
cost for the new TER was developed. This cost was then broken into 20 years (project life),
factoring in interest and annual maintenance costs. If the annual benefits (cost associated with
money saved on accident reduction) are greater than the annual costs (cost to construct and
maintain TER on a yearly basis), then construction of the TER is economically justified. The
larger the ratio, the more justified the construction. With a benefit/cost ratio of 4.27, the TER
along US 60 at MP 291.6 was considered to be cost effective and justified as a safety
improvement.
The preliminary plans called for an ascending grade arrester bed TER, of length roughly 540 feet
with an initial grade of –6% and a final grade of +10%. The aggregate would transition from an
initial depth of six inches to a maximum depth of 48 inches in the first 150 feet, and maintain 48
inches for the final 390 feet. The arrester bed is 34 feet wide, with a 13.5-foot service road
between the TER and the mainline, that reconnects with the through movement. Wrecker
anchors are provided on both sides of the TER spaced 150 feet apart. The arrester bed basin is
composted of 4” of CTB and has a cross slope of 1%. A “Last Chance” device is placed at the
end of the arrester bed measuring 30’Wx20’Dx6’H (See Figure 3.2.14).
Figure 3.2.14
US Route 60 CLOSE Report Plan and Profile (ADOT)
Initial Project Assessment, US 60, Salt River Canyon Truck Ramp, August 2001
This Project Assessment (PA) is the result of the CLOSE Report discussed above.
Truck Escape Ramp Study 3-27
The PA notes that the truck escape ramp (TER) will be designed in compliance with ADOT’s
Roadway Design Guidelines (1996) and Truck Escape Ramp Policy (1987). The TER will
consist of a 34-foot arrester bed section, 13.5-foot service road, and two 4-foot walkways on
each side of the arrester bed (See Figure 3.2.15). The TER will begin at approximately MP
290.80. Advance signing for the TER will be provided in accordance with ADOT Standard
Drawing 4-S-1.16.
The PA states that the total length of the TER will consist of the 150-foot transition from six
inches to 48 inches (arrester bed depth) along with the length determined utilizing the equation
shown in ADOT’s Roadway Design Guidelines, Section 209.4.
Although the guidelines require a minimum entering speed for a TER of 90 mph, the PA used 50
mph as the design speed, which was approved by the State Traffic Engineer during the scoping
stage.
The total length of the TER presented in the PA is 610 feet, including approximately 140 feet for
the ramp terminal, 450 feet for the arrester bed (including transition length) and 20 feet for the
secondary retarder. The entering grade is –4.3113% and the final grade of the TER is +3.0000%
(See Figure 3.2.16). The remaining dimensions reflect those of the CLOSE Report, with the
exception of the arrester bed basin cross slope, which now is presented with a normal crown
cross slope of 1%. The ramp has a preliminary cost estimate of $2,222,000.
Figure 3.2.15
US Route 60 Project Assessment (PA) Typical Section (ADOT)
Truck Escape Ramp Study 3-28
Figure 3.2.16
US Route 60 Project Assessment (PA) Plan and Profile (ADOT)
Summary
For over 20 years, the Arizona Department of Transportation (ADOT) has been studying the
effects of constructing truck escape ramps (TERs) along sustained downgrades, as well as the
parameters that go into TER design itself. From the first TER constructed in Arizona along US
89 in 1983 their value has been weighed not only by the amount of use the ramps get, but by the
decrease in the number of truck related accidents on those downgrade; primarily the reduction of
fatal accidents associated with runaway trucks.
Over the years, ADOT has fluctuated in many ways with its preferred design policies as they
relate to TERs. Some information presented 20 years ago remains unchanged today, while other
information, based on studies in state as well as around the country, has changed.
The determination of need for truck escape ramps (TERs) in Arizona is one area where the
theory has not changed much over the past 20 years. The primary indicator of a runaway truck
problem has always been the history of runaway truck accidents. Secondary indicators have
changed slightly over the years, and include smoking/hot brakes, interviews with DPS Officers,
professional truck drivers, wrecker operators and inspection of accident records. Occasionally it
was observed that various documents also determined if the improvement was economically
warranted to determine if the need was met.
The determination of location of the TER received a great deal less discussion over the past 20
years than did the determination of need. Current policy presented in the Roadway Design
Guidelines states that TERs should be located on the lower half of a downgrade, where they can
Truck Escape Ramp Study 3-29
theoretically intercept up to 80% of the runaway vehicles. Several studies have indicated that the
location of TERs is largely governed by topography. Additionally, reports have stated that
existing roadway alignment and high accident locations also play a large part in the
determination of location.
Many of the design standards used have changed over the years, with new concepts being added
as theory and research on TERs increased. The Roadway Design Guidelines present the most
recent policy on TER design. Prior to these guidelines, the 1987 publication Truck Escape Ramp
Policy served as the principal reference. Fluctuations in design speed, preferred TER type,
aggregate depth, TER width, service roads and wrecker anchors are noticeable from publication
to publication.
The information published by ADOT will, in conjunction with information published by Federal
agencies, assist a great deal in preparing up-to-date policy on TER need, location and design in
Arizona.
3.2.4 Other State Agencies
As mountainous regions and steep downgrades exist outside of Arizona, other State DOTs were
researched to determine what guidelines they use in the determination of location and need for
TERs, as well as what design standards they impose. While States on both the east and west
coasts of United States use TERs, States on the west coast were researched more heavily as they
represent similar terrain, weather conditions and material types available. The following State
agencies were researched:
• California Department of Transportation (Caltrans)
• Colorado Department of Transportation (CDOT)
• Montana Department of Transportation (MDT)
• Nevada Department of Transportation (NDOT)
• North Carolina Department of Transportation (NCDOT)
• South Dakota Department of Transportation (SDDOT)
• Utah Department of Transportation (UDOT)
• Washington State Department of Transportation (WSDOT)
California Department of Transportation (Caltrans)
The Caltrans Highway Design Manual does not specifically detail design criteria for truck escape
ramps (TERs). The manual does refer to Traffic Bulletin No. 24 (1986), Design Guide for Truck
Escape Ramps, which provides guidelines for location and design.
Bulletin No. 24 notes that several developments within the last 40 years have led to an increased
number of runaway trucks on long, steep downgrades. First, the number of trucks on highways,
and their average weight have increased. Additionally, an increase in competition and a
reduction in profit margin may cause some truckers to reduce their overhead by reducing
maintenance. Finally, in increase in out-of-state operators, who are unfamiliar with local terrain,
is more common today than in years past.
The Bulletin recognizes two different types of TERs: gravity ramps and arrester bed ramps. It
notes that gravity ramps are nothing more than an accessible surfaced side road on an ascending
Truck Escape Ramp Study 3-30
grade. They typically require little maintenance, and there is no need for special equipment to
retrieve the vehicle. The possibility of rollbacks leading to jack knifing or re-entry of the vehicle
to the mainline traffic is a potential problem. For this reason, gravity ramps are less desirable
than arrester beds.
Arrester bed ramps vary in detail depending on the material used. The material can range from
sand to 1½ inch aggregate. The grade of the arrester bed will also influence length, with
ascending ramps providing greater stopping ability.
The primary indication of need, as expressed in the Bulletin, is the number or rate of incidents
involving runaway vehicles. The presence of steep grades and/or sharp curves usually leads to
these situations. A secondary indication is the relative number of trucks with excessively hot or
smoking brakes.
The Bulletin recommends a sequential approach to resolve the runaway truck problem. The first
step is to review the signage of the downgrade, making sure that appropriate curve and grade
signs are provided, along with recommended downhill speeds. If the problem persists, a
roadside brake check area at the summit is recommended. The brake check area allows drivers
to check equipment, read about the upcoming downgrade and provides time for the braking
systems to cool off. The final step is the installation of a TER. The Bulletin states that if none of
these steps work to reduce the risk of runaway trucks, the downgrade can be restricted, and
vehicles over a specified weight would not be permitted. It notes that this final approach is
controversial.
Where a new highway is being constructed, there are no statistics to support the implementation
of a TER. In this situation, the Bulletin recommends using the figure below (See Figure 3.2.17).
If the combination of percent downgrade and length of percent downgrade fall to the right of the
plot, a TER may be warranted, otherwise, a TER should not be considered unless special
horizontal alignment conditions, such as sharp curves, exist.
The location of the TER, regardless of type, is largely dependant on terrain. The Bulletin does
note that a ramp should only be considered on the lower half of the grade, as this is where most
of the runaway situations would exist, and drivers would be more likely to utilize the ramps. The
ramps should not be located on curves; rather they should be located along a tangent section of
roadway.
When possible, the TER should have an auxiliary lane approaching the ramp. The lane should
be posted for “Runaway Vehicles Only” and “No Stopping Anytime”. They should be a
minimum of 1,000 feet long. The approach to the arrester bed should be squared off, so all
wheels of an axle enter the arresting material at the same time. The ramp should also be
constructed so that the driver of the out-of-control vehicle can see the entire ramp from the
auxiliary lane. The Bulletin notes that proper signing of the entrance to the TER is essential, and
that lighting of the ramp entrance should be considered (See Figure 3.2.18).
The width of the ramp is dependant of the TER type selected. Gravity ramps, which do not
contain the vehicle for an extended period of time, only require a width of 14 feet. While
Truck Escape Ramp Study 3-31
arrester beds, which may contain a vehicle for several hours, require a minimum width of 26
feet. The additional width of the arrester bed is to allow for multiple vehicles to use the ramp at
the same time. A 12 to 14-foot service road should be provided adjacent to the TER on the
mainline side for use by tow trucks and maintenance vehicles. The service road should be paved
and shielded from mainline traffic so it is not mistaken for a shoulder or the TER itself. Anchors
should be provided every 150 feet along the service road for use by tow trucks. Whenever
possible, the service road should return to the mainline, to allow easy return of the tow truck and
vehicle to the through roadway.
Figure 3.2.17
Guidelines for TER Need on New Highways (Caltrans)
Truck Escape Ramp Study 3-32
Figure 3.2.18
Typical Runaway Truck Ramp Signing and Marking (Caltrans)
The concept behind the arrester bed requires that the vehicle will sink into the arresting material,
thereby slowing the vehicle to a stop. To do this, the material must be unstable and have a low
bearing capacity. These properties are typically found in single graded, well-rounded stream
gravel. The aggregate used in an arrester bed should be washed, free draining uncrushed gravel
of uniform shape and size.
Fine materials are one of the principal contaminants of arrester beds. There are four main
sources: ground, surface, vehicles and the gravel itself. Paving the sides and bottom of the
arrester bed with either asphalt concrete, Portland cement concrete or a geotextile fabric, can
reduce contamination from the ground. Providing a positive means of drainage surrounding the
ramp, directing all roadway run-off from entering the arrester bed, can reduce surface
contamination. Vehicles entering the ramp can contaminate the aggregate with fluids or load
material. A positive means of draining the arrester bed and maintenance following each use will
reduce these contaminants. The aggregate itself is the final contaminant, as over time it will
weather and breakdown. For this reason, the aggregate will need to be replaced and/or
reprocessed periodically.
Experience has shown that trucks will sink at least 12 inches into the arrester bed material.
Additional experience has also shown that the lower 12 inches of material will typically become
so contaminated and compacted that it will virtually act like cement treated base. For these
reasons, the Bulletin recommends a minimum depth of material to be 36 inches, with 30 inches
being an absolute minimum. The depth of the aggregate should taper from six inches at the
beginning of the bed to maximum depth within 100 feet. This allows for gradual deceleration
and reduces the risk of loadshift.
Truck Escape Ramp Study 3-33
The Bulletin references the AASHTO Green Book for the formula to determine the desirable
length of the escape ramp. The formula sited is:
L = V2 / [30(R ± G)]
where: L = distance to stop in feet
V = entering velocity, mph
R = rolling resistance expressed as percent gradient divided by 100
G = percent grade divided by 100
A 90 mph design speed should be the minimum speed used for most situations. As an additional
safety factor, the Bulletin recommends extending the basic ramp length 25 percent.
Arrester beds should be as smooth as possible with no humps or hollows. If the full length of the
arrester bed cannot be reached, it may be necessary to provide some attenuation towards the later
part of the ramp. This can be accomplished with one or more mounds of arresting material
across the full width of the arrester bed, or by the use of crash cushions. It should be noted that
the use of crash cushions would likely increase the amount of fines entering the arrester bed.
Proper signage should be used in advance of the ramp to notify runaway truck drivers and the
traveling public of the presence of the TER. The approach and ramp should be delineated using
Class 1 delineators with red reflective sheeting. Overhead signs, preferably illuminated, should
be located prior to the ramp gore to better guide the runaway vehicle. (See Figure 3.2.18
above.)
Another desirable feature at a TER location is a telephone. The telephone should be used by
ramp users only, and thus should be hidden from view of the mainline traffic. Additionally, a
message board (blank-out or changeable) should be located upgrade from the TER to notify other
truck drivers if the TER is occupied or empty.
While gravity ramps require little maintenance, arrester beds require maintenance after every
use, as the aggregate will require smoothing and decontamination. Additionally, the gravel
should be loosened up or scarified after every ten uses or every six months, whichever is more
frequent. If excessive fine material is noted, the aggregate will either need to be replaced or
reprocessed.
Colorado Department of Transportation (CDOT)
The CDOT design manual does not contain a policy on the design of truck escape ramps (TERs),
although TERs do exist within the state of Colorado. Similarly, CDOT does not have design
standards for TERs.
Montana Department of Transportation (MDT)
The MDT design manual does not contain a policy on the design of truck escape ramps (TERs),
although TERs do exist within the state of Montana. Sample plans of TERs constructed in the
past are included below, (See Figures 3.2.19 - 3.2.23).
Truck Escape Ramp Study 3-34
Figure 3.2.19
Montana Route 287 Truck Escape Ramp Typical Section (MDT)
Figure 3.2.20
Montana Route 287 Truck Escape Ramp Plan and Profile (MDT)
Truck Escape Ramp Study 3-35
Figure 3.2.21
Interstate Route 90 Truck Escape Ramp Typical Section (MDT)
Figure 3.2.22
Interstate Route 90 Truck Escape Ram Plan and Profile 1 (MDT)
Truck Escape Ramp Study 3-36
Figure 3.2.23
Interstate Route 90 Truck Escape Ramp Plan and Profile 2 (MDT)
Nevada Department of Transportation (NDOT)
NDOT does not have specific guidelines for the installation of truck escape ramps (TERs),
although there are a number of them located throughout the State. Contact with the DOT
established past experience along with the NCHRP Synthesis of Highway Practice 178 – Truck
Escape Ramps and the AASHTO A Policy of Geometric Design of Highways and Streets as the
key factors in determining need, location and design.
NDOT currently has three TERs, all of which are of the gravel arrester bed design. Cost of
construction and terrain are sited as the two critical considerations. Experience has found that
trucks rarely travel more than 500 feet into the ramp. NDOT does not mandate that brake check
areas be provided at the summit, but where they exist, these areas contain information on the
percent grade, length of grade and location of the TER along the downgrade. NDOT does
provide signage 1 mile and ½ mile in advance of the TER. The gravel used must be clean, same
size and have proper resistance to stop the out-of-control vehicle. The State of Nevada does fine
vehicles for using the ramps, but indicates that it likely does deter usage.
The most recent TER constructed in Nevada is along SR 163 near the City of Laughlin. The
TER is a descending grade arrester bed (See Figure 3.2.24). The total ramp length is 2061 feet,
with the arrester bed making up 700 feet of the total. The TER has a “last chance” mound
constructed on the final 36 feet, with specifications indicating that the height is not to exceed 9.8
feet (See Figure 3.2.25). The grade of the TER varies from –3.409% at entry to a final slope of
–2.986% (See Figure 3.2.26).
Truck Escape Ramp Study 3-37
Figure 3.2.24
State Route 163 Truck Escape Ramp Typical Section (NDOT)
Figure 3.2.25
State Route 163 Truck Escape Ramp Plan (NDOT)
Truck Escape Ramp Study 3-38
Figure 3.2.26
State Route 163 Truck Escape Ramp Profile (NDOT)
The TER exits to the right of the mainline, with a 20-foot service road between the TER and the
roadway. Wrecker anchors are provided along the service road side spaced every 200 feet. The
aggregate varies from 4 inches at the point of entry to a maximum depth of 36 inches in the first
100 feet. The bed maintains the depth of 36 inches for the remainder of its length. The arrester
bed is lined with a plantmix bituminous surface, similar to the service road.
North Carolina Department of Transportation (NCDOT)
The NCDOT Roadway Design Manual recommends not only constructing TERs on long
mountain grades in rural areas, but also in urban areas on steep, short grades where high truck
volumes are mixed with dense traffic and development, as urban areas have a higher probability
of fatalities and property damage.
Additionally, they recommend an area at the top of the grade for truckers to check their brakes,
read information about the upcoming grade and TER, and shift to the correct gears for the
downgrade.
While NCDOT recognizes that specific warrants and processes for the justification of TERs have
not been formalized, it states the principal factor for a TER need is determined by runaway
accident experience. Conditions such as grade, length of grade, horizontal alignment and end-of-grade
conditions all weigh equally. Average daily traffic (ADT) and percent trucks also weight
about as much as the conditions above. While available right of way and topography are factors
in site selection, they are not factors in determining the need for a TER.
Truck Escape Ramp Study 3-39
NCDOT references the “Grade Severity Rating System (GSRS)” as a mechanism for
determining the need and location of TERS, as well as the NCHRP Synthesis of Highway
Practice 178 – Truck Escape Ramps and AASHTO A Policy on Geometric Design of Highways
and Streets for additional information.
South Dakota Department of Transportation (SDDOT)
The SDDOT Roadway Design Manual recommends the design and construction of a TER where
long descending grades exist or where topographical and location controls require such grades on
new alignments. It goes on to state that out-of-control vehicles are typically the result of an
operator losing control of the vehicle because of loss of brakes either through overheating or
mechanical failure, or failure to down shift at the appropriate time.
While specific guidelines for the design of TERs is lacking, the principal influence used by
SDDOT in warranting a TER is a history of runaway truck accidents. Other factors considered
are site conditions such as length of grade, percent of grade, and a combination of horizontal
alignment and end-of-grade conditions.
SDDOT references the NCHRP Synthesis of Highway Practice 178 – Truck Escape Ramps for
detailed alternatives as well as the AASHTO A Policy on Geometric Design of Highways and
Streets for design considerations. An example of a SDDOT detailed analysis is included below
(See Figure 3.2.27).
Figure 3.2.27
Escape Ramp Layout (SDDOT Figure 6-19)
Truck Escape Ramp Study 3-40
Utah Department of Transportation (UDOT)
The UDOT procedures manual does not have a policy on truck escape ramps (TERs), although
TERs do exist within the state. Similarly, there are no design standards for TERs. UDOT refers
to the AASHTO A Policy on Geometric Design of Highways and Streets for need, location and
design details.
Washington State Department of Transportation (WSDOT)
The WSDOT Design Manual (November 1999) recommends the consideration of an emergency
escape ramp whenever long steep downgrades exist. It recommends consultation with local
maintenance personnel and verification of accident records to determine if an escape ramp is
justified.
WSDOT recognizes the following types of TERs:
• Gravity escape ramps, which are ascending ramps paralleling the traveled way.
Their long length and steep grades can present drivers with control problems, and
are the least desirable design.
• Sandpile escape ramps, which are piles of loose, dry sand dumped at the ramp
site, are usually not more than 400 feet long. Their deceleration is usually high
and the sand can be affected by weather. They are more desirable than gravity
escape ramps, but less desirable than arrester beds.
• Arrester bed escape ramps, which are parallel ramps filled with smooth, coarse,
free-dra