What is the “Safety Edge” and why should we use it?

The “Safety Edge” is a 30 degree angle placed at the edge of newly installed asphalt. The purpose of the 30 degree edge is to allow drivers that drift off of the pavement surface the opportunity to safely return to the roadway. Studies have found that the typical means of applying asphalt results in a steep edge at the outer edges of the pavement surface. When erosion or wear remove the backing material of the shoulder this steep edge becomes exposed. When a driver drifts off of the pavement with the steep edge the usual attempt to return to the pavement involves a hard left turn. When the tire finally grabs the pavement edge it jumps the vehicle onto the pavement surface resulting in the vehicle surging toward the opposite lane. At higher speeds this lurching movement can send the vehicle either into oncoming traffic or across the road into a ditch or fixed object on the opposite side of the road.

Cross section of pavement with safety edge

Measuring a safety edge using a spirit level and wooden ruler
Safety Edge Measurement

The main purpose for the installation of the Safety Edge is to improve the safety along a specified roadway. Benefits of the Safety Edge are the reduction in the frequency and severity of road runoff types of accidents. Additionally, the angled edge provides better support to the pavement edge than one would typically get from a steep edge, reducing the potential for edge cracking. The application of the 30 degree angle results in an increase of asphalt by approximately 1percent since the typically loose edge is compacted, and, therefore, does not noticeably increase the cost of the pavement installation. The angle is installed by using a “shoe” placed on the paver when the pavement is placed in either new applications or overlays. The requirement for the edge should be placed within the project specifications so all bidders are aware of the requirement. The FHWA advocates the use of Safe EdgeSM because it improves the density at the pavement edge, reducing raveling.

Photograph of intersection with example of signs
GA Safety Edge Hardware

Resources

Federal Highway Administration, Every Day Counts Program
Publication Number(s): FHWA-SA-10-033, FHWA-SA-10-034

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This work by the Cornell Local Roads Program (CLRP) is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 Unported License.