midwest research institute solutions through science and technology nchrp project 15-26 passing...
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Midwest Research InstituteSolutions through science
and technology
NCHRP Project 15-26
Passing Sight Distance Criteria
April 5, 2005
2
Project Objectives
• Evaluate the design and operational criteria for determining minimum PSD
• Modify the existing criteria or develop new criteria
3
Project Scope
PSD Criteria for Geometric Design
• AASHTO Green Book
PSD Criteria for Marking of Passing and No-Passing Zones
• MUTCD
4
Project Tasks• Task 1 – Review current PSD criteria and
models
COMPLETE
• Task 2 – Review literature and research in progress
COMPLETE
• Task 3 – Identify factors that potentially contribute to PSD requirements
COMPLETE
5
Project Tasks
• Task 4 – Critique PSD criteria and develop work plan
COMPLETE
• Task 5 – Prepare interim report
COMPLETE AFTER PANEL DISCUSSIONS
6
Project Tasks
• Task 6 – Execute approved work plan
WILL BEGIN WHEN AUTHORIZED
• Task 7 – Prepare new or modified PSD criteria
WILL FOLLOW TASK 6
7
Project Tasks
• Task 8 – Prepare final report
WILL FOLLOW TASKS 6 & 7
• Task 9 – Prepare and deliver final presentations
WLL FOLLOW TASK 8
8
Project Schedule
• Planned Start Date for Phase II:
2/1/05
• Actual Start Date for Phase II:
4/6/05 ?
• Approximately two months behind schedule
9
Project Schedule
• Submit Draft Final Report
2/28/06
• Submit Revised Final Report
5/31/06
10
Outline of Presentation
• Review of Current PSD Criteria
– Section 2 of interim report
• Assessment of Current PSD Criteria and Alternative Models
– Sections 3 and 4 of the interim report
11
Outline of Presentation
• Potential Work Plans for Execution in Phase II
– Section 5 of interim report
• Priorities and Budget Allocations for Phase II
– Section 6 of the interim report
12
PSD Design Criteria
• AASHTO Green Book
PSD = d1 + d2 + d3 + d4
d1 = P-R time plus initial acceleration
d2 = distance traveled in left lane
d3 = clearance distance
d4 = distance traveled by opposing vehicle = 2/3 d2
13
PSD Design Criteria
ASSUMPTIONS
• Passed vehicle travels at uniform speed
• Passing vehicle reduces speed and trails the passed vehicle as it enters the passing section (delayed pass)
14
PSD Design Criteria
• Passing driver requires a short period to perceive the passing section and begin to accelerate:– d1 maneuver time = 3.6 to 4.5 sec (older
field data)
– d1 acceleration rate = 1.38 to 1.51 mph/sec
(2 to 2.2 ft/sec2)
15
PSD Design Criteria
• Passing is accomplished under:
– delayed start
– hurried return in the face of opposing traffic
16
PSD Design Criteria
• Left-lane distance (d2)
– average speed of passing vehicle during left-lane occupancy exceeds speed of passed vehicle by 10 mph
• at low speeds, passing vehicle above design speed, passed vehicle below design speed
• at speeds of 55 mph or more, both vehicles below design speed
– left-lane occupancy time = 9.3 to 7.3 sec, depending on speed (older field data)
17
PSD Design Criteria
• Clearance distance (d3)
– 100 to 300 ft, depending upon speed
• Opposing vehicle distance (d4)
– d4 = d2 would allow for completion of passing maneuver without need to abort
– d4 = 2/3 d2 will require abort in some cases
18
PSD Design Criteria
CRITIQUE
• AASHTO model is extremely conservative:
– If model were d1+ d2+ d3+ d2, passing driver would know that no abort is required even before beginning to pass
– If model d1+ d2+ d3+ 2/3 d2, an abort is potentially required only very early in the maneuver
19
PSD Design Criteria
• Inclusion of P-R and initial acceleration distance (d1) is very conservative:
– passing maneuver could be aborted easily and safely if opposing vehicle appears during d1
– an opposing vehicle that appears during d1 is a long way from the passing vehicle
20
PSD Design Criteria
• Ending section of adequate PSD when PSD falls below d1+ d2+ d3+ 2/3 d2 is extremely conservative:– at the end of the section of adequate
PSD, a passing driver has almost enough sight distance to start a pass and complete it without the need to abort
– passes can be started safety beyond this point, if the passing driver can abort the maneuver, if an opposing vehicle appears
21
PSD Design Criteria
• Assumption of passed vehicle speed substantially less than design speed, particularly for design speeds of 55 mph or more, is not conservative
• Assumption of constant speed differential between passing and passed vehicles, independent of design speed is questionable
22
PSD Marking Criteria
MUTCD
• presents warrants for no-passing zones
• passing zones merely happen where no-passing zones are not warranted
• where the distance between successive no-passing zones is less than 400 ft, no-passing markings should connect the zones
23
PSD Marking Criteria
• There is no quantitative model for the MUTCD criteria
• MUTCD criteria were first developed in a 1940 AASHO policy
24
PSD Marking Criteria
MUTCD/1940 AASHO ASSUMPTIONS
• no P-R time needed for pass initiation because passing driver can abort the maneuver if an opposing vehicle appears
• speed of passing vehicle is equal to 85th percentile speed or posted or statutory speed limit
25
PSD Marking Criteria
• speed differential between passing and passed vehicle ranges from 10 to 25 mph, with higher speed differentials at higher speeds
• speed of opposing is 5 to 15 mph less than speed of passing vehicle, with higher speed differentials at higher speeds
• compromise between PSD values for delayed and flying passes
26
PSD Marking Criteria
CRITIQUE
• Speed of passing vehicle equal to 85th percentile speed or speed limit is conservative:
– many passing vehicles may travel faster
27
PSD Marking Criteria
• Speed differential between passing and passed vehicles that increases with increasing speed is not conservative
– it seems more likely that speed differential would decrease as the speed of the passed vehicle increases
28
PSD Marking Criteria
• Speed of opposing vehicle less than 85th percentile speed or speed limit seems unrealistic
• Consideration of flying passes is not conservative
• Minimum 400-ft passing zones are not compatible with delayed passes on high-speed highways
29
Comparison of PSD Criteria
0
500
1000
1500
2000
2500
3000
30 40 50 60 70 80
Speed (mph)
Pa
ss
ing
Sig
ht
Dis
tan
ce
(ft
)AASHTO Green Book MUTCD
30
Comparison of PSD Criteria
Speed
(mph)
AASHTO
PSD (ft)
MUTCD
PSD (ft)
40 1,470 600
50 1,835 800
60 2,135 1,000
70 2,480 1,200
31
Comparison of PSD Criteria
AASHTO Criteria
• Driver eye height =3.50 ft
• Target height =3.50 ft (reduced from 4.25 ft in 2001)
MUTCD Criteria
• Driver eye height = 3.50 ft
• Target height = 3.50 ft
32
International PSD Criteria
PSD Design Criteria @ 100 km/h• Australia (more than US at beginning of PSD, less
than US at end of PSD)
• Austria (about the same as the US)
• Britain (less than US at beginning of PSD, much less at end of PSD)
• Canada (about the same as the US)
• Germany (slightly less than the US)
• Greece (slightly less than the US)
• South Africa (about the same as the US)
33
International PSD Criteria
PSD Marking Criteria @ 100 km/h
• Australia (slightly less than the US)
• Britain (less than the US)
• Canada (more than the US)
• South Africa (about the same as the US)
34
Safety Performance for Passing Maneuvers
• HSIS study (1994) found that:
– passing-related accidents constitute 2% of total non-intersection accidents on rural two-lane highways
– passing-related accidents are more severe than non-passing related accidents
35
Safety Performance for Passing Maneuvers
• Fatal and serious injury accidents:
– 13.9% of passing-related accidents
– 9.4% of total accidents
• Passing-related accidents are estimated to constitute 3% of total fatal and serious injury accidents on rural two-lane highways
36
Safety Performance for Passing Maneuvers
• FARS 2003 data:– 13,000 fatal accidents/year at non-
intersection locations on rural two-lane highways
– if 3% are passing-related accidents, there are 390 fatal passing-related accident per year
• Not all passing-related accidents involve limited PSD
37
Safety Performance for Passing Maneuvers
COLLISION TYPES FOR PASSING-RELATED ACCIDENTS
• Single-vehicle ROR 30%
• Sideswipe, same direction 25%
• Sideswipe, opp direction 7%
• Rear-end 17%
• Head-on 7%
• Other/unknown 15%
38
Safety Performance for Passing Maneuvers
• Safety record of passing-related accidents is generally good
• It is unlikely that safety performance of rural two-lane highways can be modified significantly by changing PSD criteria
• Potential cost-effectiveness of changes to PSD criteria need be investigated
39
PSD Criteria in Relation to the Good Safety Record of Passing Maneuvers
• PSD design criteria are conservative
• PSD values used in marking criteria are more appropriate than they seem
• Short 400-ft passing zones may not be often used for high-speed passes
• Most drivers may be conservative in making passing judgments
• A buffer area is present downstream of every passing zone
40
d1 + 2d2 + d3
Critical Position
Position of the Passing Vehicle
Pass
ing S
ight
Dis
tance
Sight distance needed to abort
pass
Sight distance needed to complete
pass
d1 + d20
Conceptual Presentation of the Changes in Sight Distance Needed to Complete or Abort a Passing Maneuver as the Passing Maneuver Progresses
d1 + d2 + d3 + 2/3 d2
AASHTO
MUTCD
41
Critical Position in the Passing Maneuver
• Models based on the critical position assume that drivers may abort the passing maneuver until the critical position is reached
42
Critical Position in the Passing Maneuver
• Critical position concept– any passing driver who has not yet
reached the critical position must have sufficient PSD to abort the maneuver
– any passing driver who has passed the critical position must have sufficient PSD to complete the maneuver
– any passing driver at the critical position must have sufficient PSD to complete or abort the maneuver
43
Critical Position in the Passing Maneuver
• Two models based on the critical position provide PSD values similar to the MUTCD:
– Glennon (1988)
– Hassan et al. (1996)
44
Critical Position in the Passing Maneuver
• First recognized by VanValkenburg and Michael (1971)– they called it the point of no return
– they visually identified the critical position as occurring when the vehicles are approximately abreast (rear bumper of passed vehicle opposite middle of passing vehicle)
– field measurements of distance traveled by the passing vehicle from the abreast position to the completion of the pass
45
Critical Position in the Passing Maneuver
• Weaver and Glennon (1972)
– defined the critical position as the point at which the time required to complete the maneuver is equal to the time required to abort the maneuver
– proposed a PSD model that did not incorporate this definition
– stated that critical position occurs when vehicles are approximately abreast
46
Critical Position in the Passing Maneuver
• Harwood and Glennon (1976)
– defined the critical position as the point at which the sight distance required to complete the maneuver is equal to the sight distance required to abort the maneuver
– proposed a PSD model that did not incorporate this definition
47
Critical Position in the Passing Maneuver
• Lieberman (1982)
– used critical position concept in modeling PSD
– defined needed PSD as d7 + PSDc
– d7 is distance to from the start of the pass to the critical position
– formulated a model to determine the relative position of the passing and passed vehicles at the critical position (Δc)
– model for Δc appears incomplete
48
Critical Position in the Passing Maneuver
• Saito (1984)
– postulated that there are two possible locations of the critical position in a passing maneuver:
• head-to-tail position (head of passing vehicle opposite tail of passed vehicle)
• abreast position (passing vehicle alongside passed vehicle)
– model inputs are not fully stated
49
Critical Position in the Passing Maneuver
• Glennon (1988)
– formulated PSD model based on equivalent sight distance to complete and abort a passing maneuver from the critical position
– included an explicit model to calculate the relative positions of the passing and passed vehicles at the critical position (Δc)
50
Critical Position in the Passing Maneuver
• Glennon (1988)
– included terms for the lengths of the passing and passed vehicles
– incorporated speed differential between passing and passed vehicles that decreases as speed increases
– deceleration rate in abort maneuver = 8 ft/sec2 (as opposed to 11 ft/sec2 in SSD)
51
Critical Position in the Passing Maneuver
m
ΔL2.932VPSD cp
d
1/2
d
pid
d
pipc m)1.47d(2V
LL2.93m4V
m)1.47(2V
LL2.93m1.47mLΔ
52
Critical Position in the Passing Maneuver
• Harwood and Glennon (1989)
– used Glennon model with some changes in input data from Glennon (1988):
• passenger car length, 19 ft rather than 16 ft
• truck length 75 ft
• smaller speed differential for truck as the passing vehicle
• lower deceleration rate in aborting a pass, 5 ft/sec2 for a truck, as opposed to 8 ft/sec2 for a passenger car
53
Critical Position in the Passing Maneuver
0
500
1000
1500
2000
2500
3000
30 40 50 60 70 80
Speed (mph)
Pa
ss
ing
Sig
ht
Dis
tan
ce
(ft
)
MUTCD Glennon
54
Critical Position in the Passing Maneuver
• Rilett at al. (1989)
– recommended a minimum speed for passing abort maneuver: Vd – 2m
– inclusion of a minimum speed substantially lengthens PSD values
– Good et al. (1991) stated that it is unreasonable to expect that, in the face of an opposing vehicle, the passing driver would decelerated to Vd – 2m and then continue at constant speed
55
Critical Position in the Passing Maneuver
• Rilett at al. (1989)
– recommended headway after pass abort greater than the 1 sec used by Glennon
– 1 sec headway appears appropriate for passenger cars
– headway greater than 1 sec appears needed for trucks
56
Critical Position in the Passing Maneuver
• Hassan et al. (1996)
– recommended two modifications to the Glennon model
– recommended incorporation of P-R time for pass abort decision (but this may already be part of the Glennon model)
– recommended providing PSD for pass completion where critical position occurs with passing vehicle ahead of passed vehicle (positive value of Δc)
57
Critical Position in the Passing Maneuver
2h)(tV5.88
tdtpt a
d
aaaac
m)(2V1.47d
m)1.47h(2VLLV5.88hht
da
dipd2a
h)t(V93.2PSD cdc
58
Critical Position in the Passing Maneuver
5pc tm47.1h m) V(47.1L
59
Critical Position in the Passing Maneuver
m
Lhm) 1.47(Vt pd*
c
h) t(V 93. 2 PSD *cdc
60
Critical Position in the Passing Maneuver
0
500
1000
1500
2000
2500
3000
30 40 50 60 70 80
Speed (mph)
Pa
ss
ing
Sig
ht
Dis
tan
ce
(ft
)
MUTCD Hassan et al. Glennon
61
Buffer Area Downstream of Passing Zones
Beginning of passing
zone
End of passing
zone
Passing maneuvers in Dir
1 must legally end here
Passing maneuvers in Dir 1 can safely end
hered5
Buffer Zone
Dir 1
Dir 2
62
Buffer Area Downstream of Passing Zones
• Buffer area results from “short zone” marking concept:
– passes must legally be completed prior to end of zone
– drivers can complete passes safely even if in critical position at end of zone
– used in 46 of the 50 states
63
PSD Marking Criteria
• HSIS study suggests no major safety problems associated with PSD marking criteria
• Glennon and Hassan et al. models suggest that MUTCD criteria may be about right, but for the wrong reason
• Differences between Glennon and Hassan et al. models need to be resolved
64
PSD Marking Criteria
• Cost of changing PSD criteria would be substantial – remeasuring PSD for all two-lane roads with centerlines
• Cost-effectiveness of potential changes in marking criteria needs to be resolved
65
Potential Approach to PSD Marking Criteria
IF SUPPORTED BY PHASE II RESULTS
• Retain MUTCD criteria
• Offer a better engineering rationale for the MUTCD criteria based on the Glennon model, the Hassan et al. model, or some variation of these models
66
Potential Approach to PSD Marking Criteria
• Consider need to change 400-ft minimum passing zone length
67
Short Passing Zones
• Can’t accommodate delayed passes on high-speed highways
• May accommodate some flying passes
• May accommodate passing very slow-moving vehicles – “tractor on the road”
• May not contribute much to LOS
• Do drivers use short zones legally? safely?
68
Short Passing Zones
• Jones (1970)
– Texas roadways with 70-mph speed limits
– field studies at three passing zones with lengths of 400, 640, and 880 ft
– comparative data for passing zones with lengths of 1,640 and 2,600 ft
69
Short Passing Zones
• Jones (1970)
– defined passing opportunity as:
• trailing vehicle within 4 car lengths (80 ft)
• appeared to be awaiting a change to pass
• average of 125 passing opportunities observed per zone
70
Short Passing Zones
Length of Passing Zone (ft)
Passing Opportunities Accepted
Slightly
Forced
Return
Very Severe Return
400 9% 37% 26%
640 9% 45% 0%
880 9% 10% 0%
1,640 23%
2,600 40%
71
PSD Design Criteria
• What is the rationale for use of longer PSD values in design than in marking?
• Does the good safety record of passing maneuvers indicate that current marking criteria are sufficient for safety?
• Does the use of longer PSD values in design than in marking enhance safety?
• Should the design process explicitly consider the passing and no-passing zones that will be marked on the completed highway?
72
Potential Alternative Approaches to PSD Marking Criteria
• #1 – Retain current AASHTO Green Book criteria
• #2 – Use the same PSD criteria for design as for marking
• #3 – Use PSD criteria for design with a defined relationship to PSD criteria for marking:
PSD = X + PSDc
73
Potential Alternative Approaches to PSD Marking Criteria
• #4 - Use the same PSD criteria for design as for marking, but count only passing sections with specified minimum length
• #5 – Use longer value of PSD to define beginning of passing section and shorter PSD to define end of passing section
74
Other Issues
• Trucks
• Older drivers
75
PSD for Trucks
0
500
1000
1500
2000
2500
3000
20 30 40 50 60 70
Design Speed (mph)
Pa
ss
ing
Sig
ht
Dis
tan
ce
(ft
)AASHTO Green Book MUTCD
Passenger Car passing Passenger Car Passenger Car passing Truck
Truck passing Passenger Car Truck passing Truck
76
PSD for Trucks
Passing Scenario
PSD needed for design speed of 60
mph (ft)
PC passing PC 1,025
PC passing Truck 1,250
Truck passing PC 1,375
Truck passing Truck 1,575
77
PSD for Trucks
• Glennon model may need longer headway after abort for truck as passing vehicle
• Truck can pass PC on any vertical curve where PC can pass a truck – reevaluate in light of changed object heights
78
PSD for Trucks
• PC passing truck or truck passing PC may not be a logical design or marking scenario:– would eliminate some current passing zones
and shorten others
– would prohibit some passes of PCs that are safe and are currently legal
– would reduce LOS
– might encourage illegal passes
– no indication of safety benefits
79
Older Drivers
• Reduced P-R time
• Reduced visual acuity
• Reduced ability to judge distances and speeds
• Less likely to travel at high speeds
• Less likely to pass
• Less aggressive
• More likely to drive passed vehicle than passing vehicle
80
PSD for Older Drivers
• FHWA Highway Design Handbook for Older Drivers recommended using Green Book PSDs instead of MUTCD PSDs
• NCHRP Project 20-7(118) recommended caution in implementing this Handbook recommendation
81
PSD for Older Drivers
• Use of longer PSD in marking would eliminate some current passing zones and shorten others
• Older drivers would still probably be more reluctant than younger drivers to pass
• Handbook recommendation did not consider the safety “cushion” provided by the buffer area
82
Key Considerations in Changing PSD Criteria
• Safety considerations (effect on accident frequency and severity)
• Traffic operational considerations (effect on level of service)
• Economic considerations (benefits to compensate for increased costs) on both existing and new highways
• Rationality and consistency of PSD criteria (understanding and acceptance by engineers)
83
Potential Phase II Work Plans
• A – Benefit-cost analysis
• B – Identify and analyze of passing-related accidents
• C – Review accident data for field sites
• D – Safety of passing maneuvers completed beyond the end of a passing zone
84
Potential Phase II Work Plans
• E – Safety and operations of short passing zones
• F – Field data to quantify parameters of revised PSD models
• G – Application of PSD criteria to actual terrain
• H – Traffic operational effects of alternative PSD criteria
85
Potential Phase II Work Plans
• I – Comparison of PSD and SSD criteria
• J – Guidance on determination of percentage of roadway length
with PSD
86
A – Benefit-Cost Analysis for Changing PSD Marking Criteria
• Objective:
– determine whether safety benefits could possibly justify cost of remeasuring PSD
– need to quantify:• cost per mile of remeasuring PSD
• number of miles of two-lane roads with marked centerlines
• number of accidents equivalent to cost of remeasuring
• number of accidents available for reduction
87
B—Identification and Analysis of Passing-Related Accidents
• Objective: Conduct further evaluation of passing-related accidents
• Identify passing-related accidents in manner similar to HSIS study
• Obtain more complete severity data
• Estimate available PSD at accident sites
• Determine portion of passing zone (or no-passing zone) where accidents occur
88
B—Identification and Analysis of Passing-Related Accidents
• Investigate involvement of trucks
• Investigate involvement of older drivers in passing, passed, and opposing vehicles
• Determine weather and pavement conditions under which passing-related accidents occur
89
C—Review of Accident Data for Field Sites
• Objective:
– Assure that field sites used in Work Plans D and F do not have adverse accident experience
– Determine accident experience for field sites in Work Plan E
90
D—Safety of Maneuvers Completed Beyond the End of a Passing Zone
• Objective: Determine the extent and consequences of pass completions beyond the end of a passing zone
• Sites to be used:– passing zone length: 1,000 to 2,500 ft
– frequent passing activity
– no-passing zone for at least 2,000 ft downstream of passing zone
91
D—Safety of Maneuvers Completed Beyond the End of a Passing Zone
• Data to be collected:– percent of maneuvers completed in marked
passing and no-passing zones
– relative positions of passing and passed vehicles at the end of the passing zone
– location of passing vehicle’s return to normal lane
– sight distance at return to normal lane
– traffic conflicts or severity of return maneuver
• Video recording and manual observation
92
E—Safety and Operations of Short Passing Zones
• Objectives: Determine whether short passing zones:– create safety problems
– contribute substantially to LOS
• Sites to be used:– passing zone length: 400 to 800 ft
• Data to be collected:– similar to Work Plan D
93
F—Quantify Parameters of Revised PSD Models
• Objective: Quantify parameters of alternative models– speed differential between passing
and passed vehicles
– distance traveled by the passing vehicle from the beginning of passing zone to the critical position
– deceleration rate use in aborting a passing maneuver
94
F—Quantify Parameters of Revised PSD Models
• Data collection approach:
– Video recording
– Manual observation
– Traffic classifiers or laser guns for speed measurement
95
G—Application of Revised PSD Criteria to Actual Terrain
• Objective: Investigate effects of changing PSD design and marking criteria
• Obtain plan and profile data for actual terrain:
– as-built plans
– Washington HSIS data
96
G—Application of Revised PSD Criteria to Actual Terrain
• How will revised PSD criteria change:– percentage of roadway length that meets
design PSD criteria
– percentage of roadway length in marked passing zones
– lengths of passing zones
– PSD available within passing zones
• Relative contributions of PSD criteria and terrain
97
G—Application of Revised PSD Criteria to Actual Terrain
• Interviews with experienced designers:
– choice of target percentage of roadway length that meets design PSD criteria
– application of design criteria
98
H—Traffic Operational Effects of Alternative PSD Criteria
• Objective: How will revised PSD design and marking criteria affect the level of service on two-lane highways?
• Tool: TWOPAS traffic operational computer simulation model
99
I– Comparison of PSD and SSD Criteria
• Compare PSD values used in design and marking to SSD values used in design
• Compare resulting vertical curve lengths in light of:
– sight distance criteria
– assumed driver eye height
– assumed object height
100
J– Guidance on Percentage of Roadway Length with Design PSD
• Provide guidance or recommendations on average frequency of passing opportunities that should be provided on two-lane highways– dependent on traffic volumes
– dependent on vehicle mix
– needs to implement desired LOS for functional class and terrain
101
J– Guidance on Percentage of Roadway Length with Design PSD
• Added passing lanes along the road may reduce the need for PSD to maintain LOS between passing lanes
102
Project Budget
Phase I $ 64,066
Phase II 235,934
TOTAL $300,000
103
Phase I Budget
• Budgeted expenditures:$64,066
• Actual expenditures (est.) 61,000
• Unexpended funds (est.) 3,066
104
Allocation of Phase II Budget
Task
Description
Original Budget
Revised Budget
6 Execute work plans $177,873 $180,939
7 Prepare new or modified PSD criteria
23,968 23,968
8 Prepare final report 25,890 25,890
9 Prepare and deliver final presentations
8,203 8,203
Total $235,934 $239,000
105
Cost Estimates for Task 7 Work Plans
• A – Benefit-cost analysis of PSD $ 10,000
marking revisions
• B – Identification and analysis of 100,000
passing-related accidents
• C – Review of accident data for 5,000
field study sites
• D – Safety of passing maneuvers 30,000
completed beyond the end
of the passing zone
106
Cost Estimates for Task 7 Work Plans
• E – Safety and operations of $ 30,000
short passing zones
• F – Field data collection to quantify 50,000
PSD models
• G – Application of revised PSD 10,000
to actual terrain
• H – Traffic operational effects 15,000
of alternative PSD criteria
107
Cost Estimates for Task 7 Work Plans
• I – Comparison of PSD and SSD $ 5,000 criteria
• J – Guidance on determining the 10,000
percentage of roadway length
with adequate PSD
• TOTAL $265,000
108
Cost Estimates for Task 7 Work Plans
• Estimated cost for all 10 work plans = $265,000
• Available funds for Task 7
= $181,000
• Difference
= $84,000
109
Potential Modifications
• Eliminate Work Plan B entirely– saves $100,000
– frees up $16,000 for field work
• Scale back Work Plan B to $16,000– existing data bases only
– no videolog review
– no hard-copy accident report review