The Safety Edge
Targeted at severe roadway departure crashes.- Crashes involving pavement edge drop-offs greater than 2.5 inches – more severe and more likely to be fatal than other roadway departure crashes.
- Pavement edges – may contribute to a significant portion of roadway departure crashes on rural roads with narrow shoulders.
The Safety Edge is targeted at reducing severe roadway departure crashes and improving pavement durability. Recent studies have shown that crashes involving pavement edge drop-offs greater than 2.5 inches are more severe and two to four times as likely to be fatal than other roadway departure crashes. Research between 2002 and 2004 show that pavement edges may have been a contributing factor in as many as 18% of rural run-off-the-road crashes in Iowa and 25% in Missouri on roads with shoulders less than four feet.
- Paving technique where the interface between the roadway and graded shoulder is paved at an angle to eliminate vertical drop-off.
- 30 degree angled wedge.
- Created by fitting resurfacing equipment with a device that extrudes the shape of the pavement edge as the paver passes.
- Very low cost countermeasure.
- Should be incorporated in all Federal-Aid new paving and resurfacing projects.
The Safety Edge is a specific asphalt paving technique where the pavement edge is paved at an optimal angle of 30 degrees to eliminate vertical drop-offs that occur during construction and re-emerge over the life of the pavement. The edge should not be left exposed following construction. The adjacent material is to be re-graded flush with the top of the pavement surface. This material will settle during the ensuing months and may be further eroded or worn down by tires in some locations. When exposed, the Safety Edge prevents very serious crashes that can occur with vertical pavement edges.
A Safety Edge shape can be readily attained by fitting resurfacing equipment with a device that extrudes the shape of the pavement edge as the paver passes. This mitigates shoulder pavement edge drop-offs immediately during the construction process and over the life of the pavement. This consolidated edge has been shown to improve pavement edge durability as well.
It is a very low cost countermeasure, requiring only a slight change to the paving equipment. The process captures asphalt mix that would otherwise be wasted, so there is very little additional material used in the process. Paving proceeds at the normal rate and there are no additional operations.
States should implement policies and procedures that incorporate the Safety Edge where pavement and non-pavement surfaces interface on all Federal-Aid new paving and resurfacing projects. The Safety Edge will provide an additional safety factor when the adjacent non-paved surface settles, erodes, or is worn down.
Note: The process can also be used on concrete pavements, by modifying conventional concrete forming attachments. The materials cost is somewhat higher for concrete pavements.
Safety Edge Effectiveness
Research in the early 1980’s found a 45 degree pavement wedge effective in mitigating the severity of crashes involving pavement edge drop-offs. During the Georgia DOT Demonstration project, evaluation of wedge paving techniques found it beneficial to flatten the wedge to a 30 degree angle resulting in a pavement edge referred to as the Safety Edge. Subsequent research has shown this design to be even more effective than the original 45 degree wedge.
The best estimate for in-service evaluation is a reduction of 5.7% of total crashes.
Safety Edge Resources
Every Day Counts Web Page
FHWA Office of Safety
Cathy Satterfield
FHWA Resource Center
Frank Julian
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