In 1998, the American Association of State Highway and Transportation Officials (AASHTO) approved its Strategic Highway Safety Plan. This plan was developed with the assistance of the Federal Highway Administration (FHWA), the National Highway Traffic Safety Administration (NHTSA), and the Transportation Research Board (TRB). The goal of this plan is to reduce highway fatalities on our nations roadways by 5,000 to 7,000 each year to 1.0 per 100 million vehicle miles traveled. This will be accomplished by the application of low-cost, proven countermeasures that, when implemented, will lead to a reduction in the number of motor vehicle crashes each year. To provide a structure for executing this plan, a 22-volume implementation guide has been developed under the direction and guidance of the National Cooperative Highway Research Program (NCHRP).

NCHRP is an agency of TRB. The guide, NCHRP Report 500: Guidance for Implementation of the AASHTO Strategic Highway Safety Plan, addresses a specific type of collision in each volume. Examples include: Aggressive Driving Collisions, Collisions caused by Drivers with Suspended or Revoked Licenses, Collisions with Trees in Hazardous Locations, Head-On Collisions, Unsignalized Intersection Collisions, and Run-Off-Road Collisions. Each volume also gives guidance for the implementation of low-cost countermeasures proven to mitigate the specific collision addressed. For example, Volume 6: A Guide for Addressing Run-Off-Road Collisions, addresses countermeasures for mitigating the number and the severity of collisions caused by vehicles leaving the roadway. In this volume, one specific type of run-off-road collision addressed is a collision caused by a pavement edge drop-off. The research described in this report, Safety Impacts of Pavement Edge Drop-offs, focuses on the magnitude and severity of such collisions, evaluates federal and state guidance regarding when edge drop-offs should be addressed, and provides measures for the quantity and depth of edge drop-offs on representative rural two-lane roadways in the United States. This information is necessary and required for states and counties to determine the economic benefits from addressing pavement edge drop-offs, to understand the importance of this aspect of the AASHTO Strategic Highway Safety Plan, and to subsequently focus the limited maintenance resources necessary to mitigate this roadway problem.

This report, and the preceding study, The Elimination or Mitigation of Hazards Associated with Pavement Edge Drop-offs During Roadway Resurfacing, by J. B. Humphreys and J. A. Parham, published in 1994, was initiated and primarily funded by the AAA Foundation for Traffic Safety (AAAFTS) to reduce the injuries and loss of life annually occurring on our nations roadways. It contains, in Chapter 6, research initiated and funded by FHWA in support of the nations goals to improve traffic safety. This joint report is an important addition to the knowledge base necessary to quantify the safety and economic benefits derived from implementing a portion of the AASHTO Highway Strategic Plan  namely a reduction in crashes precipitated by pavement edge drop-offs.