2003 CLIMBING LANE
PRIORITIZATION UPDATE
Submitted by:
Final
May 14, 2004
Prepared For:
Report
i
TABLE OF CONTENTS
Page
1. PROJECT OVERVIEW ...............................................................................1
PURPOSE.................................................................................................. 1
PREVIOUS METHODOLOGY........................................................................ 1
OVERVIEW OF REVISED METHODOLOGY ................................................... 2
2. CLIMBING LANES ON TWO-LANE HIGHWAYS........................................... 3
OVERVIEW ............................................................................................... 3
PROCESS .................................................................................................. 4
SUMMARY OF FINDINGS ........................................................................... 9
3. CLIMBING LANES ON MULTILANE HIGHWAYS....................................... 13
OVERVIEW ............................................................................................. 13
PROCESS ................................................................................................ 13
SUMMARY OF FINDINGS ......................................................................... 20
APPENDIX - RANKING METHODOLOGY....................................................... 25
REFERENCES ............................................................................................. 28
ii
LIST OF TABLES
Page
1. DATA ITEMS AND SOURCES....................................................................... 3
2. CLIMBING LANE LOCATIONS ON TWO-LANE HIGHWAYS RECOMMENDED BY
ADOT DISTRICTS ...................................................................................... 5
3. PRELIMINARY LIST OF CANDIDATE LOCATIONS FOR
CLIMBING LANES ON TWO-LANE HIGHWAYS.............................................. 6
4. PERFORMANCE CRITERIA FOR RANKING CANDIDATE
CLIMBING LOCATIONS ON TWO-LANE HIGHWAYS ...................................... 7
5. ULTIMATE LIST OF CLIMBING LANE LOCATIONS ON
TWO-LANE HIGHWAYS............................................................................ 10
6. RANKING OF CANDIDATE LOCATIONS FOR
CLIMBING LANES ON TWO-LANE HIGHWAYS............................................ 11
7. CLIMBING LANE LOCATIONS ON MULTILANE
HIGHWAYS RECOMMENDED BY ADOT DISTRICTS..................................... 15
8. PRELIMINARY LIST OF CANDIDATE LOCATIONS FOR
CLIMBING LANES ON MULTILANE HIGHWAYS.......................................... 16
9. PERFORMANCE CRITERIA FOR RANKING CANDIDATE
CLIMBING LANE LOCATIONS ON MULTILANE HIGHWAYS ......................... 18
10. ULTIMATE LIST OF CLIMBING LANE LOCATIONS ON
MULTILANE HIGHWAYS.......................................................................... 21
11. RANKING OF CANDIDATE LOCATIONS FOR CLIMBING LANES ON
MULTILANE HIGHWAYS.......................................................................... 23
iii
LIST OF FIGURES
Page
1. CLIMBING LANE CANDIDATE LOCATIONS
FOR TWO-LANE HIGHWAYS..................................................................... 12
2. CLIMBING LANE CANDIDATE LOCATIONS
FOR MULTILANE HIGHWAYS................................................................... 24
Lima & Associates 2003 Arizona Climbing Lane Prioritization Update – Page 1
1. PROJECT OVERVIEW
PURPOSE
The Arizona Department of Transportation (ADOT) is required to compile a list of projects
for its Five-Year Construction Program. This study identifies and prioritizes climbing lane
projects to be considered for inclusion in the Five-Year Construction Program. A process for
prioritizing both climbing and passing lanes on the Arizona State Highway System was
developed by the 1999-2000 Climbing/Passing Lane Study. A list of prioritized climbing and
passing lane projects was produced using the prioritization process. The 2003 study
documented here updates the 1999-2000 prioritization of climbing lane projects.
Listed below is the Technical Advisory Committee (TAC) that provided guidance on the
project. All of the ADOT Engineering Districts also contributed to the overall study process.
• Arnold Burnham, Priority Programming Manager, Transportation Planning Division
• Ron Casper, Safford District Engineer
• John Louis, Intermodal Transportation Division
• Donald Mauller, Priority Programming Team
• Jeff Swan, Holbrook Engineering District
PREVIOUS METHODOLOGY
The following documents conducted in 1999 and 2000 on prioritizing climbing lanes were
reviewed and updated:
• Technical Supplement: Passing Lanes/Climbing Lanes, September 1999
• Passing Lanes/Climbing Lanes: Preliminary Report, January 2000
• Passing Lanes/Climbing Lanes Supplemental Paper, June 26, 2000
In the previous study, climbing lanes were analyzed only on multilane highways. Candidate
climbing lane locations were identified by using ADOT’s Global Positioning System (GPS)
data to find roadway segments with grades over 2.0 percent. Adjacent sections were then
merged into 39 sections. The 39 sections were ranked using the following criteria: current
annual average daily traffic (AADT), 2020 AADT, truck volume, level-of-service (LOS),
percent grade, and total accidents. Data for the criteria were obtained from available ADOT
databases. Level-of-service was estimated based on a table of volume-to-capacity ratios versus
service volumes from the 1997 Highway Capacity Manual (HCM). For ranking the candidate
locations, points were assigned to each criterion for each project. For example, each project
received points for current AADT, 2020 AADT, truck volume, level-of-service, percent
grade, and total accidents. A total score for each candidate location was computed by
summing the points for all the criteria and the candidate locations were ranked by ascending
score.
Lima & Associates 2003 Arizona Climbing Lane Prioritization Update – Page 2
Identified Issues
The following methodology issues for climbing lanes were identified during the 1999-2000
study.
• Reliability of the GPS data to identify grades
• Reliability of the traffic volumes and truck volumes
• Identification of candidate climbing lanes for two-lane highways in addition to
candidates for multilane highways
• Estimation of level-of-service using AADT does not adequately reflect traffic
conditions. Traffic volumes must be adjusted for seasonal variation.
• Lack of local jurisdiction input during the process of identification and ranking
OVERVIEW OF REVISED METHODOLOGY
Most of the issues mentioned in the previous study to identify and rank candidate climbing
lane locations are addressed in this update. For the purpose of this study, a climbing lane is
defined as:
Additional lane on steep upgrades to facilitate the passing of trucks and slow
moving vehicles whose speed drops because of the sustained grade rather than a
lack of passing opportunity over a long stretch of highway.
For both two-lane highways and multilane highways, sustained steep upgrades result in
queuing and poor performance. In lieu of costly widening projects, and in most cases, adding
a climbing lane at these locations alleviates the problem. Hence for this study, climbing lanes
were considered on both two lane and multilane highways. The following summarizes the
steps for identifying and prioritizing climbing lanes on two-lane highways and multilane
highways.
1. Identify the “universe” of candidate locations
2. Verify the “universe” of candidate locations meet the minimum criteria required for a
climbing lane
3. Compare “universe” to climbing lane candidate locations recommended by ADOT
engineering districts
4. Select preliminary list of candidate locations from the “universe”
5. Filter preliminary list of candidate locations
6. Rank preliminary candidate climbing lanes
7. Compare preliminary candidates with candidates identified by ADOT districts
8. Review of preliminary candidates by ADOT districts
9. Prepare ultimate list of ranked candidate locations for climbing lanes after districts
review
Lima & Associates 2003 Arizona Climbing Lane Prioritization Update – Page 3
2. CLIMBING LANES ON TWO-LANE HIGHWAYS
This chapter presents the methodology for identifying and ranking candidate locations for
climbing lanes on two-lane highways. Locations identified for climbing lanes in this project
represent only the general problem area and not the exact location and length of the
climbing lanes.
OVERVIEW
The previous study did not address the aspect of climbing lanes on two-lane highways.
However this study identifies climbing lane locations on two-lane highways. Special emphasis
was given to the data collection and validation aspects of this study. Data from various
sources at ADOT was collected, as shown in Table 1. Geographic Information System (GIS)
and database software were used for data integration and analysis.
TABLE 1. DATA ITEMS AND SOURCES
Data Items ADOT Data Source
Number of Travel Lanes Roadway Log
Annual Average Daily Traffic HPMS/Historical Traffic Volume Database
Percent Grade GPS Data
Length of Grade GPS Data
Passing Length, No Passing Length Striping Database
Directional Distribution HPMS/Historical Traffic Volume Database
K Factor HPMS/Historical Traffic Volume Database
Seasonal Adjustment Factors ADOT Data Center
Truck Percentage HPMS/Historical Traffic Volume Database
Highway Geometrics Roadway Log
Speed Roadway Log
Terrain HPMS
Accidents ALISS Accident Database – Traffic Records
One of the sources used to evaluate climbing lanes on two-lane highways was the American
Association of State Highway and Transportation Officials (AASHTO) Policy on Geometric
Design of Highways and Streets, which suggests that climbing lanes on two-lane highways be
considered if all the following criteria exist:
• The directional flow rate on the upgrade exceeds 200 vehicles per hour (vph)
• The directional flow rate for trucks on the upgrade exceeds 20 vph
• Any one of the following conditions: a speed reduction of 10 mph for a typical heavy
truck, LOS E or F on the grade, or a reduction of two or more levels-of-service from
the approach segment to the grade.
Lima & Associates 2003 Arizona Climbing Lane Prioritization Update – Page 4
PROCESS
Using the data items listed in Table 1 and following the steps itemized below, a “universe” of
preliminary candidate locations and ultimate list of candidate locations were identified.
Step 1: Identify the “Universe” of Candidate Locations
For two-lane highways, the “Universe” of candidate climbing lane locations was identified by
selecting segments having a grade over 2.5 percent and a length of at least 500 ft. As
mentioned above, one of the criteria for a climbing lane is the speed reduction of at least 10
mph for a typical truck on an upgrade. According to procedures described in the 2000
Highway Capacity Manual, a segment with a grade of approximately 2.5 percent can cause a
truck to lose 10 mph speed over a longer grade length and, similarly, a segment with a grade
length of approximately 500 ft can cause a typical truck to lose 10 mph speed over a steeper
grade. To account for every scenario, all sections that had a grade of over 2.5 percent and a
grade length of 500 ft were selected. A large number of sections satisfied the above criteria
and most of them were adjacent sections. To further reduce the list of candidates, adjacent
sections were combined. Candidates greater than a mile in length were split into separate
segments. For analysis purposes, the segments were then rounded to a standard length of one
mile each to create the “Universe” of candidate locations.
Step 2: Verify the “Universe” of Candidate Locations Meet the Minimum Criteria
Required for a Climbing Lane
Using GIS, data items mentioned in Table 1 were integrated and estimated for all sections in
the “Universe” of candidate locations. These locations were then checked to see if they met
the remaining minimum criteria for climbing lanes i.e., directional flow rate on upgrade
exceeds 200 vph, and directional flow rate for trucks on the upgrade exceeds 20 vph.
Candidates that did not meet the minimum criteria were eliminated from the “Universe.”
Step 3: Compare “Universe” to Climbing Lane Candidate Locations Recommended by
ADOT Engineering Districts
Each ADOT Engineering district was requested to compile a list of candidate climbing lane
locations based on their knowledge of highways in their districts. A comparison of the district
recommended climbing location list to the “Universe” of candidate locations revealed that
approximately 66 percent of the sections identified by the districts were within a five mile
vicinity of the candidate locations in the “Universe.” For sections that were not in the
“Universe,” data was verified against other available sources, which included comparing data
items such as traffic volumes, truck percentages, and seasonal traffic factors against historical
data. After this verification, 77 percent of district recommended sections appeared in the
“Universe” of sections. Table 2 shows the list of candidate locations recommended by ADOT
Engineering districts.
Lima & Associates 2003 Arizona Climbing Lane Prioritization Update – Page 5
TABLE 2. CLIMBING LANE LOCATIONS ON TWO-LANE HIGHWAYS
RECOMMENDED BY ADOT DISTRICTS
Route Direction BMP EMP District
S 89A NB/SB 390.00 399.00 Flagstaff
U 160 EB 312.00 313.00 Flagstaff
U 89A NB 550.00 551.00 Flagstaff
U 060 WB 265.00 266.00 Globe
U 060 EB 277.00 278.00 Globe
S 264 EB 376.00 379.50 Holbrook
U 191 SB 354.00 355.00 Holbrook
S 87 NB 269.00 270.40 Prescott
U 191 NB 138.50 143.50 Safford
BMP - Beginning Milepost, EMP - Ending Milepost
Step 4: Select Preliminary List of Candidate Locations From the “Universe”
2000 HCM procedures for two-lane highways estimate LOS based on two factors:
• Percent-Time-Spent-Following reflects the average percentage of time a vehicle on a
highway spends following other vehicles. Percent-time-spent-following is estimated
from the demand flow rate, the directional distribution of traffic, and the percentage of
no-passing zones. Formulae to estimate the percent-time-spent-following listed in the
2000 HCM were used.
• Average-Travel-Speed represents the actual speed a vehicle achieves on a highway (not
speed limit) after taking into consideration factors such as grade, percentage of no
passing zones, traffic volumes etc. Formulae to estimate the average-travel-speed
listed in the 2000 HCM were used.
The above factors reflect the effects of queuing and actual travel speed on two-lane highways.
Percent-time-spent-following and average-travel-speed were determined by data items such as
daily traffic volume, truck percentage, grade, passing/no passing length, directional
distribution factor, peak hour factor, highway geometrics, speed limit, and terrain as outlined
in the 2000 HCM. Traffic volumes were adjusted for seasonal variation. Default values as
suggested in the HCM were used where actual data was not available. Percent-time-spent-following
and average-travel-speed were the performance factors used to determine the LOS
for all candidate sections.
All segments that had a level-of-service D or worse were selected to create a list of
preliminary candidate locations for climbing lanes. Table 3 shows the preliminary list of
candidate locations for climbing lanes on two-lane highways.
Lima & Associates 2003 Arizona Climbing Lane Prioritization Update – Page 6
TABLE 3. PRELIMINARY LIST OF CANDIDATE LOCATIONS FOR CLIMBING LANES ON TWO-LANE HIGHWAYS
District Section ID Route Direction BMP EMP
District/TAC Comments
(Programmed/Viable /Not Viable)
Flagstaff S 064-WB-M254-M255 S 064 WB 254 255 Not Viable: Vicinity of Grand Canyon National Park
Flagstaff S 064-WB-M266-M267 S 064 WB 266 267 Not Viable: Vicinity of Grand Canyon National Park
Flagstaff S 064-WB-M277-M278 S 064 WB 277 278 Viable
Flagstaff S 064-WB-M280-M281 S 064 WB 280 281 Viable: Programmed - FY04 @ MP276 - MP288
Flagstaff SA089-NB-M387-M388 S 89A NB 387 388 Not Viable: Vicinity of Oak Creek Canyon
Flagstaff U 089-NB-M427-M428 U 089 NB 427 428 Not Viable: Existing 4 Lane Road
Flagstaff U 089-NB-M524-M525 U 089 NB 524 525 Viable
Flagstaff U 160-EB-M312-M313 U 160 EB 312 313 Viable
Flagstaff UA089-SB-M590-M591 U 89A SB 590 591 Viable
Globe S 177-EB-M161-M162 S 177 EB 161 162 Viable
Globe S 177-WB-M152-M153 S 177 WB 152 153 Viable
Globe S 177-WB-M159-M160 S 177 WB 159 160 Viable
Globe U 060-EB-M226-M227 U 060 EB 226 227 Viable: Programmed - FY06 @ MP212 - MP225
Globe U 060-EB-M277-M278 U 060 EB 277 278 Viable
Globe U 060-EB-M365-M366 U 060 EB 365 366 Viable: Programmed - FY04
Globe U 060-WB-M265-M266 U 060 WB 265 266 Viable
Globe U 060-WB-M308-M309 U 060 WB 308 309 Viable
Globe U 060-WB-M368-M369 U 060 WB 368 369 Viable: Programmed - FY05 @ MP366
Holbrook S 264-EB-M377-M378 S 264 EB 377 378 Not Viable: Sensitive Area
Holbrook S 264-WB-M382-M383 S 264 WB 382 383 Viable: Listed in FY 04-08 Program
Kingman S 066-EB-M105-M106 S 066 EB 105 106 Not Viable: Passing Lane Exists
Phoenix Maintenance S 088-WB-M206-M207 S 088 WB 206 207 Not Viable
Phoenix Maintenance S 088-WB-M208-M209 S 088 WB 208 209 Not Viable
Phoenix Maintenance S 088-WB-M212-M213 S 088 WB 212 213 Not Viable
Prescott S 074-WB-M20-M21 S 074 WB 20 21 Viable
Prescott S 087-NB-M268-M269 S 087 NB 268 269 Viable
Prescott S 260-EB-M277-M278 S 260 EB 277 278 Viable: Programmed - FY05
Safford U 191-NB-M141-M142 U 191 NB 141 142 Viable
Safford U 191-SB-M152-M153 U 191 SB 152 153 Viable: Programmed - FY05
Safford UX191-NB-M165-M166 U 191X NB 165 166 Not Viable: Climbing Lanes Exists – Constructed 2001
Tucson S 077-SB-M103-M104 S 077 SB 103 104 Not Viable: Passing Already Exists
Tucson S 083-NB-M42-M43 S 083 NB 42 43 Not Viable: Does Not Qualify
Tucson S 083-SB-M44-M45 S 083 SB 44 45 Not Viable: Does Not Qualify
Tucson S 083-SB-M45-M46 S 083 SB 45 46 Not Viable: Does Not Qualify
Tucson S 083-SB-M46-M47 S 083 SB 46 47 Not Viable: Does Not Qualify
Lima & Associates 2003 Arizona Climbing Lane Prioritization Update – Page 7
Step 5: Filter Preliminary List of Candidate Locations
The preliminary list of candidate locations was verified against ADOT’s current Five-Year
Construction Program projects. The “District/TAC Comments” field in Table 3 shows the
programmed projects that made the preliminary list of candidates. These candidates were
removed from the preliminary list in the ranking process.
Step 6: Rank Preliminary Candidate Climbing Lanes on Two-Lane Highways
The candidate climbing lane locations were ranked using performance criteria shown in Table
4. Level-of-service, percent-time-spent-following, and average-travel-speed were obtained
from step 4. Total accidents and passing related accidents for all preliminary candidate
locations was extracted from ADOT’s ALISS accident database for a period of five years
between 1998 and 2002. Accident rate was calculated for each segment using total accidents
and existing daily traffic volumes.
TABLE 4. PERFORMANCE CRITERIA FOR RANKING CANDIDATE CLIMBING
LOCATIONS ON TWO-LANE HIGHWAYS
Performance Criteria Maximum Number of Points
Mobility (Existing level-of-service) 5
Percent-time-spent-following 10
Average-travel-speed 5
Passing related accidents 10
Accident rate 10
The following steps were carried out to determine the relative ranks of the candidate locations:
1. For each performance criterion, a Z score, or standard score, was computed for a
candidate location. The Z score indicates how far the data for the criterion deviates
from the mean of all the candidate locations, and in which direction, plus or minus.
The Z score is helpful in comparing the relative performance of the candidates in
respect to a specific criterion, such as accidents.
2. Based on a maximum number of points for the criterion, points were computed based
on the Z score for each criterion for the candidate location. Maximum number of
points used for each criterion is shown in Table 4.
3. A total score for the candidate was computed by summing the points across the five
criteria.
4. The candidates were then rank ordered according to the total scores and placed in one
of three tiers of equal increments.
Appendix A discusses in detail the ranking methodology.
Lima & Associates 2003 Arizona Climbing Lane Prioritization Update – Page 8
Step 7: Compare Preliminary Candidates With Candidates Identified by ADOT
Districts
The preliminary candidate climbing lane locations for two-lane highways were compared with
the segments identified by the ADOT Engineering Districts. For sections that were not listed
in the preliminary candidate list, data items were verified from all available sources. Further
evaluation was conducted on a case by case basis for data items such as AADT, grade, truck
percentage etc.
Step 8: Review of Preliminary Candidates by ADOT Districts
The preliminary list of ranked candidate locations was sent to ADOT Engineering Districts to
review for the following:
• Candidate location programmed or scoped for climbing lanes or widening
• Climbing lane already exist
• Viability or constructability based on filtering criteria listed below:
Filtering Criteria
- Are there constraints in proximity to a candidate location that make the location not
viable such as intersections, turn bays, physical constraints?
- Are there opportunities to locate a climbing lane on one side of the road?
- Are bridges and culverts if they result in shoulder width restriction avoided?
- Does the climbing lane location appear logical to the driver?
- Are sections with low-speed curves avoided?
- Are climbing lanes on tangent sections where the length of the tangent exceeds the
passing sight distance avoided, so as not to delay opposing vehicles by eliminating
passing opportunities?
- Are climbing lane sections that are not feasible or cost effective avoided?
- Are sections in urban areas avoided?
The “District/TAC Comments” column in Table 3 shows the district comments regarding the
viability of each candidate location based on the filtering criteria.
Step 9: Ultimate List of Ranked Candidate Locations for Climbing Lanes After Districts
Review
After the ADOT Engineering Districts review of the preliminary candidate locations, the
ultimate list of candidate locations for climbing lanes on two-lane highways was prepared by
eliminating all segments that were either programmed or deemed not viable. The ultimate list
Lima & Associates 2003 Arizona Climbing Lane Prioritization Update – Page 9
of candidate locations was re-ranked using the procedures outlined in step 6. Table 5 presents
the rankings of the ultimate list of candidate locations for two-lane highways. The Table also
shows the data for each performance criteria, assigned points for each criterion, and total
score for candidate locations. The candidate locations were placed in one of three tiers of
equal score intervals. Tier definitions used in this process are shown at the bottom of Table 5.
Table 6 displays the ultimate list of candidate locations sorted by the rank and score obtained
for each candidate location. Figure 1 illustrates the candidate climbing lane locations, color
coded by tier, and located to the side of the highway in which the climbing lane is
recommended. For example, the climbing lane recommended on SR 87 at MP 268–269 is
displayed on the right side of the highway, meaning the climbing lane should be placed on the
northbound direction.
SUMMARY OF FINDINGS
The study identified a total of 13 potential candidate locations for climbing lanes on Arizona’s
two-lane highways. As mentioned earlier, these locations represent the general problem area
and not the exact location and length of the climbing lanes. Detailed analysis is needed to
identify the exact location and length of the climbing lane. To further assist ADOT in
prioritizing the locations, the candidates were ranked and grouped into three tiers. Tier 1
candidates represent the locations with the highest priority and Tier 3 represents candidates
with the lowest priority.
Candidate locations identified by the study were compared with those identified by ADOT
Engineering Districts as a measure to validate the methodology for current and future use.
Comparison results presented in Step 3 of the process validates the methodology used to
identify candidate locations for climbing lanes. Some segments recommended by ADOT
Engineering Districts did not qualify for the ultimate list. Some of the possible reasons
include:
• Location lacked updated data
• Location already existed in the vicinity of the general problem area
• Location was recommended considering future year traffic volumes and not existing
conditions. This study did not account for future traffic volumes.
This study recommends that ADOT use one of the following methods for future updates:
• Update the data items for current candidate locations and re-rank the locations.
• Request each ADOT Engineering District to update the candidates identified in this
study. Re-rank the new candidates using updated data.
Lima & Associates 2003 Arizona Climbing Lane Prioritization Update – Page 10
TABLE 5. ULTIMATE LIST OF CLIMBING LANE LOCATIONS ON TWO-LANE HIGHWAYS
Mobility
Percent-Time-
Spent-Following
Average-Travel-
Speed
Passing Related
Accidents Accident Rate Score, Rank, and Tier
LOS A = 0 Average 3.62 Average 80.35 Average 40.31 Average 0.54 Average 1.41 Min. Rank: 14.29
LOS B = 1 St. Dev. 0.51 St. Dev. 4.18 St. Dev 3.35 St. Dev 0.78 St. Dev. 0.95 Max Rank: 28.40
LOS C = 2 Points 5 Points 10 Points 5 Points 10 Points 10 Difference 14.11
LOS D = 3 # of Tiers: 3
LOS E = 4 Reverse point
Candidate Location Information
Climbing Lanes on Two-lane Highways
LOS F = 5 assignment
District
Initial District
Recommendation
Route
Direction
Section ID
Beginning Milepost
Ending Milepost
Existing LOS/VC
LOS Points
Assigned Points
Percent-Time-Spent-
Following
Assigned Points
Average-Travel-
Speed
Assigned Points
Passing Related
Accidents
Assigned Points
Accident Rate
Assigned Points
Score
Rank
Tier
Flagstaff No S 064 WB S 064-WB-M277-M278 277 278 D 3.0 1.49 77 3.69 43 1.83 0 3.84 0.58 3.54 14.39 12 Tier 3
Flagstaff No U 089 NB U 089-NB-M524-M525 524 525 D 3.0 1.49 78 4.01 41 2.33 0 3.84 0.89 4.07 15.74 10 Tier 3
Flagstaff Yes U 160 EB U 160-EB-M312-M313 312 313 E 4.0 3.13 85 6.69 44 1.58 2 8.14 0.94 4.17 23.71 3 Tier 1
Flagstaff No U 89A SB UA089-SB-M590-M591 590 591 E 4.0 3.13 81 5.26 36 3.57 0 3.84 0.90 4.10 19.91 7 Tier 2
Globe No S 177 EB S 177-EB-M161-M162 161 162 E 4.0 3.13 79 4.36 37 3.32 1 5.99 1.06 4.38 21.18 6 Tier 2
Globe No S 177 WB S 177-WB-M152-M153 152 153 D 3.0 1.49 76 3.28 42 2.08 0 3.84 3.53 8.72 19.41 8 Tier 2
Globe No S 177 WB S 177-WB-M159-M160 159 160 E 4.0 3.13 79 4.36 37 3.32 1 5.99 1.23 4.69 21.49 5 Tier 2
Globe Yes U 060 EB U 060-EB-M277-M278 277 278 E 4.0 3.13 86 7.14 43 1.83 1 5.99 3.04 7.86 25.95 2 Tier 1
Globe Yes U 060 WB U 060-WB-M265-M266 265 266 E 4.0 3.13 83 6.07 45 1.33 0 3.84 0.64 3.64 18.01 9 Tier 3
Globe Yes U 060 WB U 060-WB-M308-M309 308 309 E 4.0 3.13 86 7.26 38 3.07 0 3.84 1.31 4.82 22.12 4 Tier 2
Prescott No S 074 WB S 074-WB-M20-M21 20 21 D 3.0 1.49 73 2.22 40 2.58 0 3.84 1.55 5.24 15.37 11 Tier 3
Prescott Yes S 087 NB S 087-NB-M268-M269 268 269 E 4.0 3.13 85 6.94 35 3.82 2 8.14 2.19 6.37 28.40 1 Tier 1
Safford Yes U 191 NB U 191-NB-M141-M142 141 142 D 3.0 1.49 77 3.72 43 1.83 0 3.84 0.51 3.41 14.29 13 Tier 3
Range of tiers for climbing lanes on two-lane highways:
Tier Increment: 4.70 Tier 1: 28.40 - 23.70
Tier 2: 23.70 – 18.99
Tier 3: 18.99 – 14.29
Lima & Associates 2003 Arizona Climbing Lane Prioritization Update – Page 11
TABLE 6. RANKING OF CANDIDATE LOCATIONS FOR CLIMBING LANES ON
TWO-LANE HIGHWAYS
District Route Direction Section ID BMP EMP Score Rank Tier
Prescott S 087 NB S 087-NB-M268-M269 268 269 28.40 1 Tier 1
Globe U 060 EB U 060-EB-M277-M278 277 278 25.95 2 Tier 1
Flagstaff U 160 EB U 160-EB-M312-M313 312 313 23.71 3 Tier 1
Globe U 060 WB U 060-WB-M308-M309 308 309 22.12 4 Tier 2
Globe S 177 WB S 177-WB-M159-M160 159 160 21.49 5 Tier 2
Globe S 177 EB S 177-EB-M161-M162 161 162 21.18 6 Tier 2
Flagstaff U 89A SB UA089-SB-M590-M591 590 591 19.91 7 Tier 2
Globe S 177 WB S 177-WB-M152-M153 152 153 19.41 8 Tier 2
Globe U 060 WB U 060-WB-M265-M266 265 266 18.01 9 Tier 3
Flagstaff U 089 NB U 089-NB-M524-M525 524 525 15.74 10 Tier 3
Prescott S 074 WB S 074-WB-M20-M21 20 21 15.37 11 Tier 3
Flagstaff S 064 WB S 064-WB-M277-M278 277 278 14.39 12 Tier 3
Safford U 191 NB U 191-NB-M141-M142 141 142 14.29 13 Tier 3
Lima & Associates 2003 Arizona Climbing Lane Prioritization Update – Page 12
FIGURE 1. CLIMBING LANE CANDIDATE LOCATIONS FOR TWO-LANE
HIGHWAYS
Lima & Associates 2003 Arizona Climbing Lane Prioritization Update – Page 13
3. CLIMBING LANES ON MULTILANE HIGHWAYS
This chapter presents the methodology for identifying and ranking candidate locations for
climbing lanes on multilane highways. Locations identified for climbing lanes in this project
represent only the general problem area and not the exact location and length of the
climbing lanes.
OVERVIEW
This study first reviewed the previous work to identify strengths and weaknesses of the
previously defined methodology and then revised the methodology to improve the overall
prioritization process. Special emphasis was given to the data collection and validation aspects
of this study. Data from various sources at ADOT was collected, as shown in Table 3
(Chapter 2). Geographic Information Systems and database software were used for data
integration and analysis.
One of the sources used to evaluate climbing lanes on multilane highways was the AASHTO
Policy on Geometric Design of Highways and Streets, which suggests that climbing lanes on
multilane highways be considered if the following criteria exist:
• Any of the following conditions apply: a speed reduction of 10mph for a typical heavy
truck, LOS E or F on the grade, or a reduction of two or more levels of service from
the approach segment to the grade.
• AASHTO recommends that high traffic volumes be one of the primary conditions for
justifying a climbing lane on multilane highways.
PROCESS
Using the data items listed in Table 1 and following the steps mentioned below, a “Universe”
of preliminary candidate locations and ultimate list of candidate locations were identified.
Step 1: Identify The “Universe” Of Candidate Locations
For multilane highways, the “Universe” of candidate climbing lane locations was identified by
selecting segments having a grade over 2.5 percent and a length of at least 500 ft. As
mentioned above, one of the criteria for a climbing lane is the speed reduction of at least 10
mph for a typical truck on an upgrade. According to procedures described in the 2000
Highway Capacity Manual, a segment with a grade of approximately 2.5 percent can cause a
truck to lose 10 mph speed over a longer grade length, and similarly, a segment with a grade
length of approximately 500 ft can cause a typical truck to lose 10 mph speed over a steeper
grade. To account for every scenario, all sections that had a grade of over 2.5 percent and a
grade length of 500 ft were selected. A large number of sections satisfied the above criteria
and most of them were adjacent sections. To further reduce the list of candidates, adjacent
Lima & Associates 2003 Arizona Climbing Lane Prioritization Update – Page 14
sections were combined. Candidates greater than a mile in length were split into separate
segments. For analysis purposes, the segments were then rounded to a standard length of one
mile each to create the “Universe” of candidate locations.
Step 2: Verify That The “Universe” Of Candidate Locations Meet The Minimum
Criteria Required For A Climbing Lane
Using GIS analysis, data items mentioned in Table 1 (Chapter 2) were integrated and
estimated for all sections in the “Universe” of candidate locations. These locations were then
checked to see if they met the minimum criteria for climbing lanes and also have considerable
high directional service volumes. Candidates that did not meet the minimum criteria were
eliminated from the “Universe” of candidate locations.
Step 3: Compare “Universe” To Climbing Lane Candidate Locations Recommended By
ADOT Engineering Districts
Each ADOT Engineering district was requested to compile a list of candidate climbing lane
locations based on their knowledge of highways in their districts. A comparison of the district
recommended climbing location list to the “Universe” of candidate locations revealed that
approximately 84 percent of the sections identified by the districts were within a five mile
vicinity of the candidate locations in the “Universe.” For sections that were not in the
“Universe,” data was verified against other available sources. The verification process
included comparing data items such as traffic volumes, tuck percentages, and seasonal traffic
factors against historical data. After this verification, 87 percent of district recommended
sections appeared in the “Universe” of sections. Table 7 shows the list of candidate locations
recommended by ADOT Engineering districts.
Step 4: Select Preliminary List Of Candidate Locations From The “Universe”
2000 HCM procedures for multilane highways estimates LOS based on three factors:
• Density is measured in terms of passenger cars per mile per lane. It is the primary
performance measure for estimating LOS on multilane highways. Formulae to estimate
the density listed in the 2000 Highway Capacity Manual were used.
• Speed is measured in terms of mean passenger car speed (mph). Formulae to estimate
the mean passenger car speed listed in the 2000 Highway Capacity Manual were used.
• Volume to Capacity Ratio
Traffic volumes were adjusted for seasonal variation. Default values as suggested in the HCM
were used where actual data was not available. Above performance factors were used to
determine the LOS for all candidate sections. All segments that had a LOS C or worse were
selected to create a list of preliminary candidate locations for climbing lanes. Table 8 shows
the preliminary list of candidate locations for climbing lanes on multilane lane highways.
Lima & Associates 2003 Arizona Climbing Lane Prioritization Update – Page 15
TABLE 7. CLIMBING LANE LOCATIONS ON MULTILANE HIGHWAYS
RECOMMENDED BY ADOT DISTRICTS
Route Direction BMP EMP District
I 15 NB 2.09 4.08 Flagstaff
I 15 NB 14.02 25.95 Flagstaff
I 15 SB 21.91 20.04 Flagstaff
I 17 NB 299.00 302.00 Flagstaff
I 17 NB 304.00 311.50 Flagstaff
I 40 EB 149.6 153.00 Flagstaff
I 40 EB 153.00 155.50 Flagstaff
I 40 EB 155.50 160.20 Flagstaff
I 40 WB 162.72 161.10 Flagstaff
I 40 EB 178.44 179.93 Flagstaff
I 40 EB 188.00 189.00 Flagstaff
I 40 WB 195.03 191.00 Flagstaff
I 40 WB 206.21 205.09 Flagstaff
I 40 WB 234.00 237.60 Holbrook
I 40 252.10 255.80 Holbrook
I 40 EB 285.20 289.50 Holbrook
I 40 EB 45.25 48.85 Kingman
I 40 EB 48.85 51.50 Kingman
I 40 EB 57.37 59.73 Kingman
I 40 WB 74.95 71.40 Kingman
I 40 EB 75.39 87.90 Kingman
I 40 EB 93.05 96.77 Kingman
I 40 WB 114.24 110.26 Kingman
I 40 EB 124.74 130.83 Kingman
I 40 WB 136.49 132.00 Kingman
S 87 SB 206.00 205.00 Phoenix Maintenance
I 17 SB 239.61 237.01 Prescott
I 17 NB 239.73 240.98 Prescott
I 17 NB 244.71 250.17 Prescott
I 17 NB 256.14 259.87 Prescott
I 17 NB 269.68 274.90 Prescott
I 17 NB 278.38 280.00 Prescott
I 17 SB 287.97 281.26 Prescott
I 17 NB 288.45 289.69 Prescott
I 17 NB 292.05 296.40 Prescott
I 17 SB 293.94 291.70 Prescott
I 17 NB 298.01 310.93 Prescott
I 40 EB 106.22 109.95 Prescott
I 10 WB 304.71 301.85 Safford
I 10 EB 309.80 312.00 Safford
I 10 EB 316.01 317.26 Safford
I 10 WB 323.96 320.86 Safford
I 10 EB 286.82 292.53 Tucson/Safford
I 8 EB 17.12 19.11 Yuma
I 8 WB 20.95 18.84 Yuma
I 8 EB 28.27 29.39 Yuma
Lima & Associates 2003 Arizona Climbing Lane Prioritization Update – Page 16
TABLE 8. PRELIMINARY LIST OF CANDIDATE LOCATIONS FOR CLIMBING LANES ON MULTILANE HIGHWAYS
District Section ID Route Direction BMP EMP
District/TAC Comments
(Programmed/Viable /Not Viable)
Flagstaff I 015-NB-M19-M20 I 015 NB 19 20 Viable
Flagstaff I 015-NB-M21-M22 I 015 NB 21 22 Not Viable: Adjacent to Virgin River
Flagstaff I 015-NB-M24-M25 I 015 NB 24 25 Viable
Flagstaff I 017-NB-M300-M301 I 017 NB 300 301 Viable
Flagstaff I 017-NB-M306-M307 I 017 NB 306 307 Viable: Viable from MP307 to MP308
Flagstaff I 017-NB-M310-M311 I 017 NB 310 311 Viable
Flagstaff I 017-NB-M330-M331 I 017 NB 330 331 Viable: Viable from MP332 to MP333
Flagstaff I 017-SB-M318-M317 I 017 SB 318 317 Viable: Viable from MP317 to MP316
Flagstaff I 040-EB-M150-M151 I 040 EB 150 151 Viable
Flagstaff I 040-EB-M157-M158 I 040 EB 157 158 Not Viable: Interchange at MP157.5
Flagstaff I 040-EB-M160-M161 I 040 EB 160 161 Viable
Flagstaff I 040-EB-M188-M189 I 040 EB 188 189 Viable
Flagstaff I 040-WB-M164-M163 I 040 WB 164 163 Not Viable: Urban Interchange
Flagstaff I 040-WB-M194-M193 I 040 WB 194 193 Viable
Kingman I 040-EB-M108-M109 I 040 EB 108 109 Viable
Kingman I 040-EB-M127-M128 I 040 EB 127 128 Viable
Kingman I 040-EB-M47-M48 I 040 EB 47 48 Viable: Could Widen to Median and Use Median Barrier
Kingman I 040-EB-M58-M59 I 040 EB 58 59 Viable
Kingman I 040-EB-M76-M77 I 040 EB 76 77 Viable
Kingman I 040-EB-M80-M81 I 040 EB 80 81 Viable
Kingman I 040-EB-M83-M84 I 040 EB 83 84 Not Viable: 4 Bridges to Widen - Not Cost Effective
Kingman I 040-EB-M88-M89 I 040 EB 88 89 Viable: Programmed FY03
Kingman I 040-WB-M116-M115 I 040 WB 116 115 Viable
Kingman I 040-WB-M134-M133 I 040 WB 134 133 Viable
Kingman I 040-WB-M137-M136 I 040 WB 137 136 Viable
Kingman I 040-WB-M73-M72 I 040 WB 73 72 Viable
Kingman U 093-SB-M67-M68 U 093 SB 67 68 Not Viable: Climbing Lane Already Exists
Prescott I 017-NB-M246-M247 I 017 NB 246 247 Viable
Prescott I 017-NB-M253-M254 I 017 NB 253 254 Viable
Prescott I 017-NB-M258-M259 I 017 NB 258 259 Viable
Lima & Associates 2003 Arizona Climbing Lane Prioritization Update – Page 17
TABLE 8. PRELIMINARY LIST OF CANDIDATE LOCATIONS FOR CLIMBING LANES ON MULTILANE HIGHWAYS
(CONTINUED)
District Section ID Route Direction BMP EMP
District/TAC Comments
(Programmed/Viable /Not Viable)
Prescott I 017-NB-M273-M274 I 017 NB 273 274 Viable
Prescott I 017-NB-M294-M295 I 017 NB 294 295 Viable
Prescott I 017-SB-M240-M239 I 017 SB 240 239 Viable
Prescott I 017-SB-M257-M256 I 017 SB 257 256 Viable
Prescott I 017-SB-M283-M282 I 017 SB 283 282 Viable
Prescott I 017-SB-M288-M287 I 017 SB 288 287 Viable
Safford I 010-EB-M310-M311 I 010 EB 310 311 Viable
Safford I 010-WB-M304-M303 I 010 WB 304 303 Viable: Programmed FY06
Safford I 010-WB-M325-M324 I 010 WB 325 324 Viable
Yuma I 010-EB-M7-M8 I 010 EB 7 8 Viable
Lima & Associates 2003 Arizona Climbing Lane Prioritization Update – Page 18
Step 5: Filter Preliminary List Of Candidate Locations
The preliminary list of candidate locations was verified against ADOT’s current Five-Year
Construction Program projects. The “District/TAC Comments” field in Table 8 shows the
programmed projects that made the preliminary list of candidates. These candidates were
removed from the preliminary list in the ranking process.
Step 6: Rank Preliminary Candidate Climbing Lanes On Multilane Highways
The candidate climbing lane locations were ranked using performance criteria shown in Table
9. Level-of-service, density, and average-travel-speed were obtained from step 4. Total
accidents for all preliminary candidate locations were extracted from ADOT’s ALISS accident
database for a period of five years between 1998 and 2002. Accident rate was calculated for
each segment using total accidents and existing daily traffic volumes.
TABLE 9. PERFORMANCE CRITERIA FOR RANKING CANDIDATE CLIMBING
LANE LOCATIONS ON MULTILANE HIGHWAYS
Performance Criteria Maximum Number of Points
Mobility (level-of-service) 5
Traffic density (passenger cars/mile/lane) 10
Accident rate (based on total accidents) 10
The following steps were carried out to determine the relative ranks of the candidate locations:
1. For each performance criterion, a Z score, or standard score, was computed for a
candidate location. The Z score indicates how far the data for the criterion deviates
from the mean of all the candidate locations, and in which direction, plus or minus.
The Z score is helpful in comparing the relative performance of the candidates in
respect to a specific criterion, such as accidents.
2. Based on a maximum number of points for the criterion, points were computed based
on the Z score for each criterion for the candidate location. Maximum number of
points used for each criterion is shown in Table 9.
3. A total score for the candidate was computed by summing the points across the four
criteria.
4. The candidates were then rank ordered according to the total scores and placed in one
of three tiers of equal increments.
Appendix A discusses in detail the ranking methodology.
Lima & Associates 2003 Arizona Climbing Lane Prioritization Update – Page 19
Step 7: Compare Preliminary Candidates With Candidates Identified By ADOT Districts
The preliminary candidate climbing lane locations for multilane highways were compared with
the segments identified by the ADOT Engineering Districts. For sections that were not listed
in the preliminary candidates list, data items were verified from all available sources. Further
evaluation was conducted on a case by case basis for data items such as AADT, grade, truck
percentage etc.
Step 8: Review Of Preliminary Candidates By ADOT Districts
The preliminary list of ranked candidate locations were sent to ADOT Engineering Districts
for review of the following-
• Candidate location programmed or scoped for climbing lanes or widening
• Climbing lane already exist
• Viability or constructability based on filtering criteria listed below:
Filtering Criteria
- Are there constraints in proximity to a candidate location that make the location not
viable such as intersections, turn bays, physical constraints?
- Are there opportunities to locate a climbing lane on one side of the road?
- Are bridges and culverts if they result in shoulder width restriction avoided?
- Does the climbing lane location appear logical to the driver?
- Are sections with low-speed curves avoided?
- Are climbing lanes on tangent sections where the length of the tangent exceeds the
passing sight distance avoided, so as not to delay opposing vehicles by eliminating
passing opportunities?
- Are climbing lane sections that are not feasible or cost effective avoided?
- Are sections in urban areas avoided?
The “District/TAC Comments” column in Table 8 shows the district comments regarding the
viability of each candidate location based on filtering criteria.
Step 9: Ultimate List Of Ranked Candidate Locations For Climbing Lanes After
Districts Review
After the ADOT Engineering Districts review of the preliminary candidate locations, the
ultimate list of candidate locations for climbing lanes on multilane highways was prepared by
eliminating all segments that were either programmed or deemed not viable. The ultimate list
of candidate locations was re-ranked using the procedures outlined in step 6. Table 10
Lima & Associates 2003 Arizona Climbing Lane Prioritization Update – Page 20
presents the rankings of the ultimate list of candidate locations for multilane highways. The
Table also shows the data for each performance criteria, assigned points for each criterion,
and total score for candidate location. The candidate locations were placed in one of three
tiers of equal score intervals. Tier definitions used in this process are shown at the bottom of
Table 10. Table 11 displays the ultimate list of candidate locations sorted by the rank and
score obtained for each candidate location. Figure 2 illustrates the candidate climbing lane
locations color, coded by tier, and shown on the side of the highway in which the direction of
lane is recommended. For example, the climbing lane recommended on I-17 at MP 300-301
is displayed on the right side of the highway, meaning the climbing lane should be placed on
the northbound direction.
SUMMARY OF FINDINGS
The study identified a total of 34 potential candidate locations for climbing lanes on Arizona’s
multilane highways. As mentioned earlier, these locations represent the general problem area
and not the exact location and length of the climbing lanes. Detailed analysis is needed to
identify the exact location and length of the climbing lane. To further assist ADOT in
prioritizing the locations, the candidates were ranked and grouped into three tiers. Tier 1
candidates represent the locations with the highest priority and Tier 3 represents candidates
with the lowest priority.
Candidate locations identified by the study were compared with those identified by ADOT
Engineering Districts as a measure to validate the methodology for current and future use.
Comparison results presented in Step 3 of the process validates the methodology used to
identify candidate locations for climbing lanes. Some segments recommended by ADOT
Engineering Districts did not qualify for the ultimate list. Some of the possible reasons are:
• Location lacked updated data.
• Location already existed in the vicinity of the general problem area.
• Location was recommended considering future year traffic volumes and not existing
conditions. This study did not account for future traffic volumes.
This study recommends that ADOT use one of the following methods for future updates:
• Update the data items for each candidate location and re-rank the locations.
• Request each ADOT Engineering District to update the candidates identified in this
study. Re-rank the new candidates using updated data.
Lima & Associates 2003 Arizona Climbing Lane Prioritization Update – Page 21
TABLE 10. ULTIMATE LIST OF CLIMBING LANE LOCATIONS ON MULTILANE HIGHWAYS
Mobility Accident Rate Density Score, Rank, and Tier
LOS A = 0 Average 2.68 Average 0.35 Average 26.84 Min. Rank: 8.41
LOS B = 1 St. Dev 0.73 St. Dev 0.28 St. Dev 5.53 Max Rank: 20.80
LOS C = 2 Points 5 Points 10 Points 10 Difference 12.39
LOS D = 3 # of Tiers: 3
LOS E = 4
Candidate Location Information
Climbing Lanes on Multilane Highways
LOS F = 5 District
Initial District
Recommendation
Route
Direction
Section ID
BMP
EMP
Mobility
LOS Points
Assigned Points
Accident Rate
Assigned Points
Density
Assigned Points
Score
Rank
Tier
Flagstaff Yes I 015 NB I 015-NB-M19-M20 19 20 C 2.0 1.72 0.31 4.77 23 3.90 10.40 25 Tier 3
Flagstaff Yes I 015 NB I 015-NB-M24-M25 24 25 C 2.0 1.72 0.46 5.68 20 2.81 10.21 26 Tier 3
Flagstaff Yes I 017 NB I 017-NB-M300-M301 300 301 D 3.0 2.87 0.36 5.07 28 5.25 13.19 13 Tier 2
Flagstaff Yes I 017 NB I 017-NB-M306-M307 306 307 C 2.0 1.72 0.57 6.29 21 3.31 11.33 22 Tier 3
Flagstaff Yes I 017 NB I 017-NB-M310-M311 310 311 D 3.0 2.87 0.79 7.60 29 5.65 16.13 3 Tier 2
Flagstaff No I 017 NB I 017-NB-M330-M331 330 331 C 2.0 1.72 0.91 8.33 23 3.87 13.92 10 Tier 2
Flagstaff No I 017 SB I 017-SB-M318-M317 318 317 C 2.0 1.72 1.05 9.12 22 3.59 14.44 6 Tier 2
Flagstaff Yes I 040 EB I 040-EB-M150-M151 150 151 D 3.0 2.87 0.34 4.94 27 5.04 12.85 15 Tier 2
Flagstaff Yes I 040 EB I 040-EB-M160-M161 160 161 C 2.0 1.72 0.71 7.10 23 3.86 12.69 16 Tier 2
Flagstaff Yes I 040 EB I 040-EB-M188-M189 188 189 D 3.0 2.87 0.62 6.59 32 6.41 15.87 4 Tier 2
Flagstaff Yes I 040 WB I 040-WB-M194-M193 194 193 D 3.0 2.87 0.02 3.08 28 5.27 11.22 23 Tier 3
Kingman Yes I 040 EB I 040-EB-M108-M109 108 109 C 2.0 1.72 0.23 4.33 21 3.33 9.39 28 Tier 3
Kingman Yes I 040 EB I 040-EB-M127-M128 127 128 C 2.0 1.72 0.21 4.17 22 3.41 9.30 29 Tier 3
Kingman Yes I 040 EB I 040-EB-M47-M48 47 48 D 3.0 2.87 0.55 6.20 26 4.76 13.83 11 Tier 2
Kingman Yes I 040 EB I 040-EB-M58-M59 58 59 C 2.0 1.72 0.20 4.16 20 2.80 8.68 32 Tier 3
Kingman Yes I 040 EB I 040-EB-M76-M77 76 77 D 3.0 2.87 0.12 3.65 29 5.59 12.11 18 Tier 3
Kingman No I 040 EB I 040-EB-M80-M81 80 81 D 3.0 2.87 0.22 4.24 34 7.09 14.20 7 Tier 2
Kingman No I 040 EB I 040-EB-M83-M84 83 84 D 3.0 2.87 0.56 6.24 27 4.93 14.04 9 Tier 2
Kingman Yes I 040 WB I 040-WB-M116-M115 116 115 C 2.0 1.72 0.00 2.96 23 3.73 8.41 34 Tier 3
Kingman Yes I 040 WB I 040-WB-M134-M133 134 133 C 2.0 1.72 0.18 4.02 22 3.41 9.15 30 Tier 3
Kingman Yes I 040 WB I 040-WB-M137-M136 137 136 C 2.0 1.72 0.08 3.41 22 3.41 8.54 33 Tier 3
Kingman Yes I 040 WB I 040-WB-M73-M72 73 72 D 3.0 2.87 0.08 3.42 29 5.59 11.88 20 Tier 3
Prescott Yes I 017 NB I 017-NB-M246-M247 246 247 E 4.0 4.02 0.97 8.66 37 8.11 20.79 2 Tier 1
Prescott Yes I 017 NB I 017-NB-M253-M254 253 254 D 3.0 2.87 0.28 4.61 31 6.23 13.71 12 Tier 2
Prescott Yes I 017 NB I 017-NB-M258-M259 258 259 D 3.0 2.87 0.29 4.66 32 6.59 14.12 8 Tier 2
Prescott Yes I 017 NB I 017-NB-M273-M274 273 274 C 2.0 1.72 0.26 4.51 21 3.21 9.44 27 Tier 3
Prescott Yes I 017 NB I 017-NB-M294-M295 294 295 D 3.0 2.87 0.16 3.93 29 5.75 12.55 17 Tier 2
Prescott Yes I 017 SB I 017-SB-M240-M239 240 239 E 4.0 4.02 0.06 3.31 37 8.19 15.52 5 Tier 2
Lima & Associates 2003 Arizona Climbing Lane Prioritization Update – Page 22
TABLE 10. ULTIMATE LIST OF CLIMBING LANE LOCATIONS ON MULTILANE HIGHWAYS (CONTINUED)
Mobility Accident Rate Density Score, Rank, and Tier
LOS A = 0 Average 2.68 Average 0.35 Average 26.84 Min. Rank: 8.41
LOS B = 1 St. Dev 0.73 St. Dev 0.28 St. Dev 5.53 Max Rank: 20.80
LOS C = 2 Points 5 Points 10 Points 10 Difference 12.39
LOS D = 3 # of Tiers: 3
LOS E = 4
Candidate Location Information
Climbing Lanes on Multilane Highways
LOS F = 5 District
Initial District
Recommendation
Route
Direction
Section ID
BMP
EMP
Mobility
LOS Points
Assigned Points
Accident Rate
Assigned Points
Density
Assigned Points
Score
Rank
Tier
Prescott No I 017 SB I 017-SB-M257-M256 257 256 D 3.0 2.87 0.09 3.49 28 5.43 11.79 21 Tier 3
Prescott Yes I 017 SB I 017-SB-M283-M282 283 282 F 5.0 5.00 0.51 5.94 43 9.86 20.80 1 Tier 1
Prescott Yes I 017 SB I 017-SB-M288-M287 288 287 C 2.0 1.72 0.21 4.20 25 4.58 10.50 24 Tier 3
Safford Yes I 010 EB I 010-EB-M310-M311 310 311 D 3.0 2.87 0.20 4.15 30 5.95 12.97 14 Tier 2
Safford Yes I 010 WB I 010-WB-M325-M324 325 324 D 3.0 2.87 0.16 3.89 27 5.15 11.92 19 Tier 3
Yuma No I 010 EB I 010-EB-M7-M8 7 8 C 2.0 1.72 0.06 3.29 23 3.93 8.94 31 Tier 3
Range of tiers for climbing lanes on two-lane highways:
Tier Increment: 4.13 Tier 1: 20.80 – 16.67
Tier 2: 16.67 – 12.54
Tier 3: 12.54 – 8.41
Lima & Associates 2003 Arizona Climbing Lane Prioritization Update – Page 23
TABLE 11. RANKING OF CANDIDATE LOCATIONS FOR CLIMBING LANES ON
MULTILANE HIGHWAYS
District Route Direction Section ID BMP EMP Score Rank Tier
Prescott I 017 SB I 017-SB-M283-M282 283 282 20.80 1 Tier 1
Prescott I 017 NB I 017-NB-M246-M247 246 247 20.79 2 Tier 1
Flagstaff I 017 NB I 017-NB-M310-M311 310 311 16.13 3 Tier 2
Flagstaff I 040 EB I 040-EB-M188-M189 188 189 15.87 4 Tier 2
Prescott I 017 SB I 017-SB-M240-M239 240 239 15.52 5 Tier 2
Flagstaff I 017 SB I 017-SB-M318-M317 318 317 14.44 6 Tier 2
Kingman I 040 EB I 040-EB-M80-M81 80 81 14.20 7 Tier 2
Prescott I 017 NB I 017-NB-M258-M259 258 259 14.12 8 Tier 2
Kingman I 040 EB I 040-EB-M83-M84 83 84 14.04 9 Tier 2
Flagstaff I 017 NB I 017-NB-M330-M331 330 331 13.92 10 Tier 2
Kingman I 040 EB I 040-EB-M47-M48 47 48 13.83 11 Tier 2
Prescott I 017 NB I 017-NB-M253-M254 253 254 13.71 12 Tier 2
Flagstaff I 017 NB I 017-NB-M300-M301 300 301 13.19 13 Tier 2
Safford I 010 EB I 010-EB-M310-M311 310 311 12.97 14 Tier 2
Flagstaff I 040 EB I 040-EB-M150-M151 150 151 12.85 15 Tier 2
Flagstaff I 040 EB I 040-EB-M160-M161 160 161 12.69 16 Tier 2
Prescott I 017 NB I 017-NB-M294-M295 294 295 12.55 17 Tier 2
Kingman I 040 EB I 040-EB-M76-M77 76 77 12.11 18 Tier 3
Safford I 010 WB I 010-WB-M325-M324 325 324 11.92 19 Tier 3
Kingman I 040 WB I 040-WB-M73-M72 73 72 11.88 20 Tier 3
Prescott I 017 SB I 017-SB-M257-M256 257 256 11.79 21 Tier 3
Flagstaff I 017 NB I 017-NB-M306-M307 306 307 11.33 22 Tier 3
Flagstaff I 040 WB I 040-WB-M194-M193 194 193 11.22 23 Tier 3
Prescott I 017 SB I 017-SB-M288-M287 288 287 10.50 24 Tier 3
Flagstaff I 015 NB I 015-NB-M19-M20 19 20 10.40 25 Tier 3
Flagstaff I 015 NB I 015-NB-M24-M25 24 25 10.21 26 Tier 3
Prescott I 017 NB I 017-NB-M273-M274 273 274 9.44 27 Tier 3
Kingman I 040 EB I 040-EB-M108-M109 108 109 9.39 28 Tier 3
Kingman I 040 EB I 040-EB-M127-M128 127 128 9.30 29 Tier 3
Kingman I 040 WB I 040-WB-M134-M133 134 133 9.15 30 Tier 3
Yuma I 010 EB I 010-EB-M7-M8 7 8 8.94 31 Tier 3
Kingman I 040 EB I 040-EB-M58-M59 58 59 8.68 32 Tier 3
Kingman I 040 WB I 040-WB-M137-M136 137 136 8.54 33 Tier 3
Kingman I 040 WB I 040-WB-M116-M115 116 115 8.41 34 Tier 3
Lima & Associates 2003 Arizona Climbing Lane Prioritization Update – Page 24
FIGURE 2. CLIMBING LANE CANDIDATE LOCATIONS FOR MULTILANE
HIGHWAYS
APPENDIX A. RANKING METHODOLOGY
Lima & Associates 2003 Arizona Climbing Lane Prioritization Update – Page 26
RANKING METHODOLOGY
The methodology used in this rating system compares basic performance data about each
project against all other submitted projects. The following categories are considered in the
methodology:
• Current level-of-service
• Future level-of-service
• Accident rates
• Strategic criteria such as Level of Development, Functional Class, and National
Highway System
The established goal categories are represented through a number of points. To start out with,
each category is assigned the same number of points, meaning that all categories are equally
important. Once data items are collected for each project the statistical procedure of a Z score
is applied to assign a certain number of points to each project. Thus, reflecting the ranking of
the particular project in each of the goal categories. In other words, the project with the
greatest need of improvement in a certain category will receive the highest number of points in
that category. This method allows ranking quantitative criteria, such as “accident rate” as
well as qualitative criteria such as the “strategic goal”. The impacts of a project on the
strategic goal are translated in a numeric value, which in turn is used to assign “criteria”
points.
Scoring
For each data category, a Z-score is calculated, which is then used to distribute category
points. For example, average and standard deviation across all projects for the mobility
category is calculated. An assigned number of points are then distributed according to the
distribution of individual values. Individual scores are then calculated for mobility, safety
(accident rate), and strategic information (subtotal of all factors). The overall score is
calculated by adding up the mobility, safety, and strategic score.
Ranking
A rank for each project is calculated based on the overall score. The project with the highest
score is ranked number 1.
Tier System
In order to avoid controversy over small differences in final project scores and subsequent
ranking a “Tier” system is applied. This system assigns each project to a group or tier.
Currently, an approach is used which creates three (3) groups or tiers based on the spread of
Lima & Associates 2003 Arizona Climbing Lane Prioritization Update – Page 27
scores. The difference between the lowest and highest project score is used to calculate the
range of project scores. This range of project scores is then divided by the number of groups
resulting in range intervals.
Example:
Score 1 = 20 highest score
Score 2 = 12
Score 3 = 17
Score 4 = 7
Score 5 = 5 lowest score
highest score minus lowest score: 20 – 5 = 15
divided by the number of tiers, assume three: 15 ÷ 3 = 5
determines range interval: Tier 3: 5-10
Tier 2: 10-15
Tier 1: 15- 20
Lima & Associates 2003 Arizona Climbing Lane Prioritization Update – Page 28
REFERENCES
American Association of State Highway and Transportation Officials, A Policy on Geometric
Design of Highways and Streets, Washington D.C., 2001.
Transportation Research Board, 2000 Highway Capacity Manual, National Research Council,
Washington D.C., 2000.
