New AAA Foundation Report Reveals Safety Impacts of Pavement Edge Drop-Offs.

WASHINGTON -- Pavement edge drop-off related crashes are substantially more likely than other crashes on similar roadways to result in serious injuries, and are more than twice as likely to be fatal, according to a recent study sponsored by the AAA Foundation for Traffic Safety.

Characterized by a shoulder that is lower than the edge of the paved road surface, pavement edge drop-off can be caused by pavement breaking, erosion and wear of unpaved shoulders, inadequate maintenance, or resurfacing projects that neglect to keep shoulders level with the paved road surface. Although they can occur on any roadway, they are more common on rural two-lane roads with narrow lanes and shoulders. A driver may be forced off the road or drive off the road for any number of reasons and pavement edge drop-off, especially if 2 inches or deeper, can increase the risk of a crash and make it difficult for a driver to return to the road safely.

Crashes related to pavement edge drop-off are relatively infrequent, but are often very severe. This research presents statistical evidence of an association between the prevalence of edge drop-off on a given roadway segment and the segment's rate of edge drop-off related crashes. Roadside inspections in two states revealed that 12 percent of drop-off measurements in one state, and 18 percent in the other state, were two inches or deeper.

Based on the analysis of crash data, the AAA Foundation report recommends that transportation agencies adopt a policy requiring routine comprehensive sampling of pavement edge drop-off on their roads, and prompt remediation of any pavement edge drop-off of depth meeting or exceeding a prescribed threshold, which should be no higher than 2 inches.

"Although several agencies at the national level provide guidance and recommendations related to edge drop-off for highway design, construction, and maintenance, no national standards exist that indicate the level at which pavement edge drop-off should be addressed," said Kissinger. "And, construction and maintenance practices related to this problem vary considerably across the country."

The report also recommends agencies adopt a policy of providing paved shoulders, with a minimum width of 2 feetCoor wider if conditions warrantCowherever practical, and endorsed the incorporation of a beveled edge, such as the Federal Highway Administration's (FHWA) Safety Edge, in all roadway resurfacing projects, to prevent the occurrence of severe drop-offs at pavement edges.

The FHWA recommends that state and local jurisdictions consider using a safety edge on resurfacing projects to help eliminate edge drop-offs. The majority of highway fatalities occur on two-lane rural roads, and these roads offer a particular opportunity for this type of treatment.

"The safety edge is a low-cost construction technique that has the potential to save lives," said John Baxter, director of the FHWA's Office of Safety Design.

Built upon an earlier study by the AAA Foundation, this research was conducted by the Iowa State University Center for Research and Education and Midwest Research Institute. Specifically, this study included an assessment of the prevalence of pavement edge drop-off on rural 2-lane roads in Missouri and Iowa, an investigation of crashes related to pavement edge drop-off, a review of transportation agency guidelines and practices for monitoring and addressing pavement edge drop-off, and a review of existing driver education and training materials that attempt to educate motorists about pavement edge drop-off hazards.

Also included in the report are results obtained from a recent, related project sponsored by the Federal Highway Administration, which analyzed the frequency and severity of crashes related to edge drop-off in North Carolina and Illinois. All of the conclusions and recommendations contained in the report were developed in conjunction with a national panel of technical experts representing key stakeholder groups.

To promote safe driving when encountering a drop-off, the AAA Foundation developed "Over the Edge and Back: What to do if you drop off the pavement edge," a brochure that explains what drivers should do, and what they should avoid doing, if they drive off the road. "It's not about returning to the road quickly, it's about returning to the road safely, according to Peter Kissinger, AAA Foundation president and CEO. "Don't panic or immediately attempt to steer back on the road, especially at high speed, as this can easily cause you to lose control of your vehicle."

The AAA Foundation for Traffic Safety is an independent, publicly funded, 501 (c)(3) charitable research and educational organization established in 1947 by AAA. The AAA Foundation's mission is to prevent traffic deaths and injuries by conducting research into their causes and by educating the public about strategies to prevent crashes and reduce the impact when they do occur. The report "Safety Impacts of Pavement Edge Drop-offs," and drop-off brochure are available on-line at www.aaafoundation.org.

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