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Proven Safety Countermeasures

Safety EdgeSM

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U.S. Department of Transportation
Federal Highway Administration

Office of Safety logo: Safe Roads for a Safer Future - Investment in roadway safety saves lives.

FHWA-SA-12-010

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Photo of a construction worker holding instruments to the edge of a newly paved roadway to measure the angle of the Safety Edge applied there.

The Safety EdgeSM is a proven technology that shapes the edge of a paved roadway at approximately 30 degrees from the pavement cross slope during the paving process. The Safety EdgeSM eliminates tire scrubbing, a phenomenon that contributes to losing control of a vehicle. It has been successfully constructed on both asphalt and concrete pavements. The Safety EdgeSM has minimal impact on project cost combined with the potential to improve pavement life.

Background

Vertical pavement edges are a recognized detriment to safety, contributing to severe crashes that frequently involve rollovers or head-on collisions. Studies in some States find that crashes involving edge drop-offs are two to four times more likely to include a fatality than other crashes on similar roads. Providing a flush, unpaved surface adjacent to the pavement resolves the issue temporarily, but the material is often displaced over time, recreating the dangerous drop-offs either continuously or intermittently along the pavement edge. Research in the early 1980s found a 45 degree pavement edge somewhat effective in mitigating the severity of crashes involving pavement edge drop-offs. However, constructing a durable edge was not perfected until the 1990s, and during development it was found that a flatter, 30 degree angle was easier to construct. Additional testing indicated that the 30 degree edge improved the chances of a safe recovery.

The Safety EdgeSM is one of the innovative technologies being deployed as part of FHWA's Every Day Counts initiative. The majority of State DOTs have built at least one project using the Safety EdgeSM, and approximately a dozen State DOTs now include it as a standard practice when paving.

An empirical Bayes evaluation published in the report Safety Evaluation of the Safety Edge Treatment (FHWA-HRT-11-024) indicates that the application of Safety EdgeSM led to an estimated reduction of 6 percent in total crashes on two-lane highways. Because of the low cost of the Safety EdgeSM, the benefit-cost ratio on two-lane roads ranges from 4 to 63.

Guidance

States should develop standards for implementing the Safety EdgeSM for all asphalt paving projects without curbs. Standard application should also be encouraged for concrete pavements. Local agencies should be encouraged to use the Safety EdgeSM on their paving and resurfacing projects as well. For asphalt pavements, it is important to provide compression as the asphalt is shaped to produce a durable edge. This can be readily attained using a specially designed device. Shoulders should still be pulled up flush with the pavement surface at project completion.

This figure shows the placement of the safety edge treatment in relationship to the new pavement surface placed during resurfacing. The safety edge treatment is shown as an asphalt wedge with a 30-degree slope. The slope is generally covered with new graded material.

Key Resources

The Safety Edge: A Pavement Edge Drop-Off Treatment, FHWA-SA-10-034
http://www.fhwa.dot.gov/everydaycounts/technology/safetyedge/brochure/brochure.pdf

FHWA Guide Specification for the Safety Edge
http://www.fhwa.dot.gov/everydaycounts/technology/safetyedge/specs.cfm

Frequently Asked Questions about the Safety Edge
http://www.fhwa.dot.gov/everydaycounts/technology/safetyedge/faqs.cfm

Safety Evaluation of the Safety Edge Treatment, HSIS Summary Report, FHWA-HRT-11-025
http://www.fhwa.dot.gov/publications/research/safety/hsis/11025/

Safety Evaluation of the Safety Edge Treatment, FHWA-HRT-11-024
http://www.fhwa.dot.gov/publications/research/safety/11024/index.cfm

Influence of Roadway Surface Discontinuities on Safety, State of the Art Report, Transportation Research Circular, Number E-C134
http://onlinepubs.trb.org/onlinepubs/circulars/ec134.pdf

Safety Impacts of Pavement Edge Drop-offs
http://www.aaafoundation.org/pdf/PEDO_report.pdf

Construction of a Safe Pavement Edge: Minimizing the Effects of Shoulder Drop-off
http://www.transtechsys.com/pdf/trb%20swm.pdf

FHWA Contacts

Office of Safety: Cathy Satterfield, cathy.satterfield@dot.gov, 708-283-3552
FHWA Resource Center (Safety): Frank Julian, frank.julian@dot.gov, 404-562-3689
FHWA Resource Center (Pavement): Chris Wagner, christopher.wagner@dot.gov, 404-562-3693
FHWA Web site: http://www.fhwa.dot.gov/everydaycounts/technology/safetyedge/intro.cfm