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The Safety EdgeDownloadable Version
PDF [2.6 MB] The Safety Edge Pavement Edge TreatmentYou Can Reduce Pavement Edge Drop-off HazardsSaves Lives Pavement Edges Can Pose Serious Safety HazardsRoadway departures account for 53 percent of fatal crashes. While national data documenting the role of pavement edge configuration in the sequence of events leading to crashes are not available, some State-level studies point to the life-saving potential of safety edges. For example, researchers studying crashes in Iowa during 2002-2004 reported that pavement edges may have been a contributing factor in as many as 18 percent of rural run-off-road crashes on paved roadways with unpaved shoulders. This type of crash was four times more likely to include a fatality than rural crashes overall on similar roads.1 How Hazardous Pavement Edges Affect Crash SeverityWhen a tire drops off a paved surface, sometimes just inches from the travel lane, a driver can have difficulty re-entering the roadway if the pavement edge is nearly vertical—especially if the height difference is significantly more than 2 inches
When a driver drifts onto the roadway shoulder and tries to steer back onto the pavement, the vertical pavement edge can create a "tire scrubbing" condition that may result in over-steering. If drivers over-steer to return to the roadway without reducing speed, they are prone to lose control of the vehicle. The vehicle may veer into the adjacent lane, where it may collide with, or sideswipe oncoming cars; overturn; or run off the opposite side of the roadway and crash. A simple and cost-effective way to promote pavement edge safety is to adopt a standard specification for all resurfacing projects that requires a 30° - 35° angle “Safety Edge.” After paving, the adjacent material is graded flush with the top of the pavement. Solutions to the Pavement Edge Drop-off Risk
The asphalt wedge provides a safer roadway edge, and a stronger interface between the pavement and the graded material. The additional cost of the asphalt wedge is minimal when included as part of resurfacing projects. Benefits include the avoided economic and social impacts of fatalities, injuries, and property damage.
The placement of the asphalt wedge during resurfacing operations mitigates the risk posed by edge drop-offs as soon as the paving machine lays down the asphalt mat, allowing the highway agency reasonable time to restore the shoulder or other adjacent graded material. Relative Safety of Various Edge Elevations and ShapesThe chart below shows how various edge shapes relate to safety at speeds of up to 55 mph. Contact the FHWA for More Information about the Safety Edge and other Roadway Departure Crash CountermeasuresFor more information about Roadway Departure issues and effective countermeasures to prevent Roadway Departure crashes, go to the FHWA Office of Safety's Web site at http://safety.fhwa.dot.gov/ and click on "Road Departure." FHWA contacts for technical assistance with the Safety Edge are listed below. ContactsFrank JulianFHWA Resource Center Chris Wagner Cathy Satterfield __________________________ 1 Hallmark et. al: Safety Impacts of Pavement Edge Drop-Offs, AAA Foundation for Highway Safety, Washington, DC, September 2006. Publication Number FHWA-SA-09-023 |
Program ContactCathy Satterfield Publications |