Safety Impacts of Pavement Edge Drop-offs

1. Safety Impacts of Pavement Edge Drop-offs

2. AAA Foundation for Traffic Safety Established in 1947 501 (c)(3) Not-For-Profit Research affiliate of AAA/CAA North American Focus

3. Mission Identify traffic safety problems Foster research that seeks solutions Disseminate information and educational materials

6. Project Advisory Panel Technical Experts and key stakeholders from: State DOTs Federal Highway Administration University Transportation Researchers Insurance Institute for Highway Safety AAA Other transportation safety researchers and advocates

7. What is Pavement Edge Drop-off? Difference in height between paved road surface and shoulder or adjacent surface Caused by: Inadequate maintenance Erosion Broken pavement Resurfacing road but not shoulder

8. The Problem If a vehicle leaves the road, edge drop-off makes it difficult to drive back on, increases crash risk Crashes related to pavement edge drop-off are a major source of tort liability claims filed against highway agencies Need research-based guidance to prevent drop-off and crashes

9. Purpose of Study To evaluate current highway agency guidelines and practices for monitoring and addressing pavement edge drop-off To assess the prevalence and depth of drop-offs To investigate frequency and severity of drop-off-related crashes To develop recommendations for reducing drop-off and decreasing risk to drivers

10. The Study Comprehensive review of published guidance for road construction and maintenance Survey of state guidelines and practices for identifying and addressing drop-off Measurement of drop-off on paved rural roads with unpaved shoulders in 2 states Inspection of Police Accident Reports for crashes possibly related to drop-off Statistical analysis of crash rates and drop-off presence in 2 states Review of driver education and training materials

11. Review of Existing Guidance Findings: There is no national standard for drop-off prevention or mitigation There is not agreement on what drop-off depth and shape is dangerous Existing guidance is not based on crash data Wide variation in maintenance practices

12. Survey of States and Provinces Surveyed 14 U.S. states and 2 Canadian provinces, finding: Shoulder paving and width varies by state and road type Most provide signage and/or barricades if there is drop-off during construction Most sample drop-off regularly Max �acceptable� drop-off varies from 1.5 to 3.0 inches

13. Frequency and Depth of Drop-off Measured drop-off along sample of 2+ mile segments of 2-lane paved rural roads in 2 states

14. Frequency and Depth of Drop-off Findings: ~0.1% of drop-off measurements > 5.0 inches deep < 1% of drop-off > 4.0 inches 1-3% of drop-off > 3.0 inches 12-19% of drop-off > 2.0 inches Note that both states consider 2-inch drop-off unacceptable

15. Drop-off Related Crashes Examined sample of Police Accident Reports from 4 states for evidence that drop-off contributed to the crash Restricted to crashes on paved rural roads with unpaved shoulders Methodology developed for related Federal Highway Administration study Analyzed sequence of events, narrative, and diagram of crash Separate regression analysis of crash density and drop-off prevalence on segments where drop-off was measured

16. Drop-off Related Crashes Findings: Drop-off may contribute to approximately 2% of crashes on paved rural roads with unpaved shoulders Crashes possibly related to drop-off are more severe than other crashes on similar roads � more than twice as likely to be fatal Density of crashes on segments increases with drop-off prevalence

17. Review of Driver Training Materials Reviewed state drivers� manuals and driver education textbooks Project panel developed recommended educational message to instruct motorists on returning to the road safely after driving over a drop-off AAA Foundation used panel recommendation to develop �Over the Edge and Back� educational brochure

18. State and local transportation agencies should provide training to maintenance and construction staff Agencies should require routine inspection of shoulder conditions and prompt remediation of any pavement edge drop-off over a certain threshold depth Threshold depth should be 2.0 inches at most Project Panel Recommendations

19. Agencies should adopt paved shoulder policy requiring paved shoulders with minimum width of 2 feet, or wider if conditions warrant Agencies should include a 30 � 35� beveled edge (e.g., FHWA Safety Edge) on all roadway resurfacing projects Project Panel Recommendations

20. States should analyze crash data to assess contribution of drop-off to crashes on their roads Data improvement may be necessary in some states More research is needed on motorist understanding of roadway-condition related signage State driver manuals should include advice on hazards of drop-off and techniques for safely re-entering the road Project Panel Recommendations

21. For more information, please go to: www.aaafoundation.org