Field Application and Assessment of the Safety Edge

Pavement edge drop-off can be a serious safety concern when a vehicle leaves the paved roadway surface and encounters a significant difference in vertical elevation between the paved roadway and the adjacent unpaved shoulder. Edge drop-offs are potential safety hazards because scrubbing between the pavement edge and tire can result in loss of control. FHWA developed the Safety Edge on the basis of research results that indicated a sloped pavement edge surface could be more easily traversed by a vehicle leaving its lane and attempting to remount the pavement edge. The Safety Edge is a design feature that creates an approximate 30° fillet along the outside edge of the paved section of a roadway. Although a number of benefits have been attributed to the Safety Edge, agencies in Iowa were slow to adopt it. To accelerate use of the Safety Edge, the research team marketed and monitored it in Iowa during the 2010 construction season. This project provided the opportunity to evaluate the Safety Edge as well as summarize lessons learned from agencies and contractors. Evaluation of the Safety Edge included assessment of the consistency of slope application, identification of common problems during construction, measurement of the density of the Safety Edge, and computation of the approximate additional material needed to construct the Safety Edge. The team also measured drop-off formation along previously constructed Safety Edge sites and compared this with control sites to assess any difference in occurrence.