1. Evaluation of Low-Cost Safety Improvements Pooled Fund Study
2017 Traffic Records Forum
Dr. Carol Tan, FHWA, and Ms. Kim Eccles, VHB

2. Presentation Overview
What are low cost safety strategies?
Background and objectives
Crash modification factors (CMFs)
Example approach
Recent results and findings
Evaluations in progress
Contacts and resources

3. Low-Cost Safety Strategies
Generally infrastructure-based strategies that agencies apply as part of Highway Safety Improvement Program.
These could be design strategies such as realigning a curve or an intersection (or pictured here, a road diet with restriping) or traffic control device improvements such as enhanced signing or markings.
Around 100K or less.

4. Background and Objectives

5. Background on ELCSI-PFS Effort
Need objective measures for effectiveness before investing
Evaluation of Low-Cost Safety Improvements Pooled Fund Study
FHWA established in 2005 to move tried and experimental to proven
Initially 24 State members and 4 phases
Goal:
To develop reliable quantitative estimates of effectiveness in reducing crashes
Effort continued in 2013 as the Development of Crash Modification Factors (DCMF) Program
Evaluates higher cost improvement also
Addressing methodological issues in CMFs and SPFs

6. 40 States in the Pool – Coast to Coast
Implement strategies
Pool resources for evaluations
Provide data on strategies (e.g. crash, roadway, volume)
Provide direction to study
Share best practices

7. CMFs and Better Decision-Making
CMFs – Crash Modification Factors
Estimates of the impact of strategies on crashes
CMFs under 1.0 represent a reduction in crashes from applying strategy
CMFs over 1.0 represent an increase in crashes
Provide method to calculate comparisons between alternatives or projects
Kim

8. CMFs and Better Decision-Making (Cont.)
CMF usage in alternative countermeasure selection
CMFs help answer the question – which pedestrian crossing strategy should I use to improve my specific midblock crossing? Each of the three strategies pictured has a different CMF.

9. CMFs and Better Decision-Making (Cont.)
CMF usage in site selection prioritizing process
CMFs help me answer the question – which of the three sites do I treat? I only have enough money to fund one project. Which one will give me the best b/c? I need to make the best use of my dollars.

10. CMFs: How do we know? Before/After Studies Cross-sectional Studies
Compare safety performance before and after infrastructure change
Numerous study designs often with some form of reference group
Cross-sectional Studies
Compares locations “with” to those “without” strategy
Locations have to be very similar in all other regards
New study design introduce techniques for this “matching”
Most CMFs studies take one of two forms – Before/after or cross sectional.

11. CMFs: How do we know?
There are a lot of sources of CMFs including this pooled fund study, NCHRP research, and research conducted by States or universities.

12. CMF Clearinghouse www.cmfclearinghouse.org FHWA Resource
Quantifiable estimates of crash impact of strategies
Up to date resource

13. Example Approach to Strategy Evaluation

14. Edge Line Rumble Strips (ELRS) on Curves
Pavement marking applied directly over rumble
ELRS applications
Milled rumble strips
Audible vibratory pavement markings

15. ELRS on Curves
Goals
Provide better visibility for nighttime, wet pavement markings
Alert motorists as they depart the travel lane
Courtesy FHWA

16. Study Design – Study Questions
What is the impact on crashes of applying this strategy?
Total
Fatal and injury
Run-off-road
Nighttime
Nighttime run-off-road
Do effects vary by type of treatment?
Do effects vary by site characteristics?

17. Study Design – Methodology
Empirical Bayes (EB) before-after
Establish reference group
Predict safety for after period assuming no treatment
Observe actual safety for after period with treatment
Compare the two
Reference group
Untreated sites adjacent to treated sites
As similar to treated sites as possible
Used to calibrate safety performance functions

18. Study Design – Initial Concerns
Spillover or Migration Effects
Spillover effect results in fewer crashes at adjacent sites after treatment
Crash migration results in more crashes at adjacent sites after treatment
Compared adjacent and non-adjacent reference sites

19. Volunteer States Florida Kentucky Mile-years of data 32 curves
6.41 miles
Audible-vibratory
Kentucky
229 curves
15.6 miles
Milled stripEs
Mile-years of data
Before
99.41 After

20. Analysis Findings
Identify impact on total crashes and several subsets (e.g., fatal and injury, run-off-road, etc.) – aggregate models
When possible, look at characteristics of sites – disaggregate models
Benefit/cost analysis
Total crash impact
Service life
Life cycle costs

21. Recent Results and Findings

22. Recent Results and Findings
Over 40 evaluations conducted to date
Edge Line Rumble Strips on Rural, Two-Lane Horizontal Curves
Intersection Multi-strategy Signalized
Intersection Multi-strategy Stop Controlled
Corner Clearance at Signalized Intersections
Profiled Thermoplastic Pavement Markings
Cable Median Barriers with Shoulder Rumble Strips
Horizontal Curve Realignment
Flashing Yellow Arrow
Right in/Right Out at Stop Controlled Intersections
Red Light Indicator Lights

23. Edge Line Rumble Strips on Rural, Two-Lane Horizontal Curves
Kentucky
Ohio
Statistic
Total
Injury
ROR
Nighttime
Nighttime ROR
Estimate of CMF
0.75*
0.64*
0.74*
0.63*
0.75
Standard error of estimate of CMF
0.09
0.14
0.11
0.19
Statistic
Total
Injury
ROR
Nighttime
Nighttime ROR
Estimate of CMF
0.79*
0.78*
0.75*
0.71*
Standard error of estimate of CMF
0.04
0.07
0.05

24. ELRS on Curves: Economic Analysis
Milled Rumble StripEs (KY)
$2,500 per mile for rumble strip
12-15 year service life
Stripe cost not added
Audible Vibratory Pavement Markings (FL)
$3,800 per mile for 6” audible vibratory marking
Unknown service life

25. ELRS on Curves: Economic Analysis
B/C Ratios
Milled Rumble StripEs
121.6
Audible Vibratory Pavement Markings
5.8 assuming 2-year service life
27.12 assuming 10-year service life

26. Intersection Multi-Strategy Applications
SCDOT statewide intersection improvement program
Initiated in 2009
8,300 intersections screened
2,200+ intersections selected
2% of all State-maintained intersections
50% of intersection crashes and fatalities
Focused on low-cost improvements
Signals, signs, and markings
Signalized Intersections (158 intersections)
Stop-controlled intersections (918)
Kim to do next series

27. Multi-Strategy: Signalized Intersections
Signal improvements
Replace signal heads (some intersections but not all)
Replace pedestrian signal heads, pushbuttons, and signs
Install backplates with retroreflective borders
Restripe stop bars and crosswalks
Install overhead signs
R10‐12
R3‐5L
R3‐5R

28. Multiple Strategies at Signalized Intersections

29. Multiple Strategies at Signalized Intersections
Disaggregate results – compared across characteristics
Appear to be more effective (total crashes)
Urban intersections vs rural (0.95 vs. 0.98)
Three legged vs four-legged (0.86 versus 0.97)
2 lane/2 lane vs. 4 lane/2 lane (0.78 versus 0.98)

30. Multiple Strategies at Signalized Intersections
Economic Analysis Assumptions and Estimates
7 year service life
Pavement marking and signing costs approximately $7,000/intersection
Signal head replacement, ped improvements ranged from $10,000-18,000/intersection
Estimated cost of AVG crash $95,186 in 2015 dollars
Use the final rev tech brief in this file to finish this slide:
\\ralnc\projects\ DCMF_TaskA\tech\Task A4\SC-Multiple Strategies\Tech Briefs\FHWA Review - Signalized\FHWA Final Review

31. Multiple Strategies at Signalized Intersections (Cont.)
Economic Analysis Results
The treatments saved 50.6 crashes/year
AVG reduction of 0.6 crashes/site/year across the 84 sites
The treatments resulted in reduction of 26.5 fatal and injury crashes, 0.3 crashes less per site per year
Various intersection treatments can be cost effective in reducing crashes.

32. Multi-Strategy: Stop Controlled
Sign improvements
Double 48” x 48” STOP and YIELD signs
Double 36” x 36” intersection warning signs
Double 48” x 48” advanced traffic control signs
Fluorescent yellow sheeting
Retroreflective sign posts
Advance street names

33. Multi-Strategy: Stop Controlled
Marking improvements
Stop bars (placed within 4 – 10 ft of edge of through lane)
Yield bars for yield conditions
Dashed white edgeline through intersection (major road)
Marked turn lanes
Lane arrows
Word “ONLY”
* As needed, remark:
Stop bars
Crosswalks
Arrows
Words

34. Multiple Strategies at Stop-Controlled Intersections

35. Multiple Strategies at Stop-Controlled Intersections – Economic Analysis
Construction cost - $5,900
7 year service life
Average cost for a stop-controlled intersection crash was $132,071 in 2017
Service Life
Lower Bound
Average B/C
Upper Bound
3 years
7.1
12.4
17.5
7 years
14.5
25.5
35.9

36. Corner Clearance at Signalized Intersections
Presented poster at TRB (Jan 2017)
Poster at Urban Streets Symposium (May 2017)

37. Corner Clearance: Data Collection
Similar to RIRO efforts (HSIS, GIS, field visit)
Initially 222 sites from California
Supplemented with 53 sites from Charlotte, NC

38. Corner Clearance Aggregate Results: Total Crashes
Number of Corners with
Driveways within 50 ft
CMF
S.E.
1 receiving corner
1.33
0.11
2 receiving corners
1.76
0.30
Bold = statistically significant at 95-percent level
Italics = statistically significant at 90-percent level

39. Corner Clearance Aggregate Results: Total Crashes
Number of Corners with
Driveways within 50 ft
CMF
S.E.
1 approach corner
0.82
0.08
2 approach corners
0.67
0.13
Bold = statistically significant at 95-percent level
Italics = statistically significant at 90-percent level

40. Number of Access Points Removed
Economic Analysis
Treatment
Remove access points within 50 ft on receiving corners
$81 per linear ft of curb and sidewalk
100 ft of curb and sidewalk = $8,100 per access point
Assumptions
Considered total crashes only
No construction of new access points
No effect for leaving existing driveways on approach corners
Number of Access Points Removed
Lower B/C
Average B/C
Upper B/C 1
94.6
172.0
237.3 2
165.9
301.7
416.3

41. Profiled Thermoplastic Pavement Markings
SC and FL provided data
CMF of for nighttime wet-road, not statistically significant at 95% confidence but consistent
A B/C of 3.65 suggests treatment can be cost effective

42. Cable Median Barriers with Shoulder Rumble Strips

43. Cable Median Barriers with Shoulder Rumble Strips
Conducted an EB before/after analysis
Illinois
Kentucky
Missouri
States differed in before conditions
Over 400 miles of installed strategy, several years of data

44. Cable Median Barriers in Combination with Rumble Strips
Kentucky, Illinois, and Missouri
Crash Type
CMF
SE of CMF
Total
1.247
0.034
Injury and fatal (KABC)
0.745
0.040
Injury and fatal (KAB)
0.783
0.073
Cross-median
0.119
0.053
This study evaluated safety effectiveness of cable median barriers in combination with rumble strips on the inside shoulder of divided roads. This strategy is intended to reduce the frequency of cross-median crashes, which tend to be very severe. Geometric, traffic, and crash data were obtained for divided roads in Illinois, Kentucky, and Missouri. To account for potential selection bias and regression-to-the-mean, an empirical Bayes before–after analysis was conducted, using reference groups of untreated roads with characteristics similar to those of the treated sites. The analysis also controlled for changes in traffic volumes over time and time trends in crash counts unrelated to the treatment. In Illinois and Kentucky, cable median barriers were introduced many years after the inside shoulder rumble strips were installed; therefore, the evaluation determined the safety effect of implementing cable barrier along sections that already had rumble strips. Conversely, in Missouri, the inside shoulder rumble strips and cable barrier were implemented about the same time. Hence, the evaluation in Missouri determined the combined safety effect of inside shoulder rumble strips and cable barriers. The combined Illinois and Kentucky results indicate about a 27-percent increase in total crashes; a 24-percent decrease in fatal, incapacitating, non-incapacitating, and possible injury crashes; a 22-percent decrease in in fatal, incapacitating, and non-incapacitating injury crashes; and a 48-percent decrease in head-on plus opposite-direction sideswipe crashes (used as a proxy for cross-median crashes). The results from Missouri for total and injury and fatal crashes were very similar to the combined Illinois and Kentucky results. However, the reduction in cross-median crashes in Missouri was much more dramatic—showing a 96-percent reduction (based on cross-median indicator only) and an 88-percent reduction (based on cross-median indicator plus head-on). The economic analysis for benefit-cost ratios shows that this strategy is cost beneficial.

45. Horizontal Curve Realignment
Curves – 33% of fatal, single vehicle crashes
Most involve striking a fixed object or overturning
Signing and striping are lower cost but have shorter service life
Source: FHWA

46. Horizontal Curve Realignment
Conducted a before-after empirical Bayes evaluation of horizontal curve realignments
California – 36 realigned curves
North Carolina – 11 realigned curves
Ohio – 15 realigned curves
Reference curves identified from nearby curves on same route as treated curves
Small but meaningful sample

47. Horizontal Curve Realignment: Data Sources
HSIS (Highway Safety Information System)
Road characteristics
Traffic volume
Crash data
Project files
Project specifics
Location verification
Map measurement
Before and after curve radius
Presence of nearby curves

48. Horizontal Curve Realignment
California
North Carolina
Ohio
Crash Type
CMF
S.E.
Total
0.3
0.1
Injury and Fatal
Run-Off-Road plus Fixed Object
0.2
Dark
0.6
Wet-Road

49. Horizontal Curve Realignment – Economic Analysis
Cost for realignment -$251,558
30 year service life, could be longer
Benefit to cost: to 1

50. Flashing Yellow Arrow
NV, NC, OK, OR

51. Flashing Yellow Arrow Category Before Phasing After Phasing Legs
Crash Type
CMF 1
Traditional PPLT
FYA PPLT on one road 3
Total
0.849*
KABC
0.791* 2 4
0.889*
0.801*
FYA PPLT on both roads
0.818*
0.782*
Permissive or Traditional PPLT
FYA permissive on one road
0.997
0.808* 5
Permissive
0.915
0.787* 6
At least one protected phase
FYA PPLT without TOD
1.051
1.011 7
FYA PPLT with TOD
0.974
1.089

52. Flashing Yellow Arrow
Cost $6,500 for 4-leg intersection, $1,625 per approach in Oklahoma
Cost $6,000 per approach in Illinois
10 year service life
Very large benefit costs, depending on treatment category – 69:1 for category 2

53. Turning Restrictions at Stop-Controlled Intersections

54. Data Collection HSIS data GIS data
Traffic data: AADT and design speed
Geometric data: # of lanes and median type
Crash data
GIS data
Access type and location
Traffic control
Turning restrictions
Enriched and verified using aerial imagery

55. Aggregate Results: RIRO Restriction
Expected crash reduction
Crash Modification Factor

56. Aggregate Results: Downstream Intersections (Signalized)
Expected crash increase
Crash Modification Factor
Expected crash reduction

57. Aggregate Results: Downstream Intersections (Stop-controlled)
Crash Modification Factor
Expected crash increase
Expected crash reduction

58. Disaggregate Analysis
Disaggregated by:
Traffic Volumes
Number of mainline lanes
Design speed on mainline
No differences detected

59. Economic Analysis Impact is highly dependent on local conditions
Hypothetical stop-controlled intersection
Downstream signal
Treatment cost
4-ft wide $6 per sq-ft ($24 per linear-ft)
Average distance = 1,210 ft (between signals)
Installation cost = $26,500
B/C ratio
9.6 (range: 5.4 – 13.5)

60. Considerations RIRO benefit Crash migration
Potential crash reduction at treated locations
More cost-beneficial when treated locations have higher safety risk compared to downstream intersections
Crash migration
Potential for crash increases at downstream intersections
Type of downstream traffic control
Signalized: smaller percent increase, not statistically significant
Stop-controlled: larger percent increase, more statistically significant
Disaggregate analysis
No differences detected

61. Red Light Indicator Lights (RLIL)
RLIL illuminates simultaneously with red signal phase
Allows enforcement to enforce downstream

62. RLIL - Results Statistic Total Fatal & injury Right-angle Left-turn
Rear-end
Disobey signal
Night
Estimate of CMF
0.939*
0.856*
0.905*
0.600*
1.016
0.713*
0.892*
Standard error of estimate of CMF
0.022
0.027
0.042
0.041
0.033
0.048
0.034
Presented poster at TRB (Jan 2017)

63. RLIL – Economic Analysis
Costs
$50 to $300 per bulb
Installation - $3,000 per intersection
5 to 10 year service life, no maintenance costs
Benefit to Cost Ratio
92:1 for four-leg signalized intersection

64. On-Going Evaluations

65. Other Strategies Under Evaluation Now
Pedestrian strategies
Prohibition of permissive left turns to improve pedestrian safety
Leading pedestrian intervals
Study locations
Chicago
New York
Toronto
Charlotte

66. Other Strategies Under Evaluation Now
Highway Friction Surface Treatments (HFST)
Provide guidance on the use of HFST to reduce roadway departure crashes.
Materials and specifications
Appropriate locations and conditions

67. Resources and Contacts

68. ELCSI-PFS
tfhrc/projects/safety/comprehensiv e/elcsi/index.cfm
Google or Bing “ELCSI-PFS” (It’s easier!)
Website has full reports and tech briefs for all evaluations
Links to related content

69. Questions? Roya Amjadi, Office of Safety R&D, FHWA project manager
Carol H. Tan, Office of Safety R&D, FHWA
Kim Eccles (contractor to FHWA)