Roadway Departure Safety

This research emphasizes two fundamental objectives:  Keeping vehicles on the roadway, and minimizing the consequences of a vehicle leaving the roadway.  FHWA’s Roadway Departure research develops and promotes strategic initiatives that decrease roadway departures, reduces the number and severity of crashes resulting from roadway departures, and enhances knowledge and the tools and methods that will support sustainable efforts to monitor, roadway departure crashes, understand their causes, and provide guidance for effective deployment of mitigation measures.  The program emphasizes the provision of technical assistance and information to Federal, State and local transportation agencies, in coordination with other stakeholder agencies.

Lane departure safety

The ideal result of any good highway design and traffic control system is that a vehicle never to leave its traveled lane except when the driver intends that maneuver. Lane departure research considers ways to provide better information to the driver about the vehicle’s position on the road surface, and to indicate to the driver when the vehicle is straying   towards a potentially dangerous situation (for example, enhanced visibility of lane markings and road signage support good decisionmaking by the driver). Measures such as rumble strips and rumble stripes provide the driver a clear warning that the vehicle is crossing a boundary between safe and potentially unsafe conditions.

Roadside safety

Roadside safety research is focused on reducing the number and severity of crashes when a vehicle leaves the road entirely.  The majority of roadside safety research at TFHRC is conducted as part of the Advanced Crash Analysis Program (ACAP). ACAP efforts are supported under a multi–year, task–order FHWA contract with the National Crash Analysis Center (NCAC) at the George Washington University (GWU) School of Engineering and Applied Science. Within ACAP, state–of–the–art computer models and crash simulations are used to study a number of topics, including the effectiveness of roadside hardware such as guardrails, sign supports, and concrete barriers; vehicle–to–vehicle impact compatibility; and the causes of rollover crashes. Simulations are validated through full–scale crash tests at the Federal Outdoor Impact Laboratory at the TFHRC. These studies result in the design and deployment of new roadside safety features, and the establishment of guidelines for the appropriate use of those safety features. ACAP researchers have developed guidelines for cable median barriers, analyzed terrain effects on vehicle trajectories as they leave the road and approach roadside hardware such as longitudinal barriers, evaluated the safety performance of commonly used roadside hardware under the proposed new crashworthiness criteria, and studied the effectiveness of portable concrete barriers.

The results of this program are freely shared and have been the basis for other safety research worldwide. The finite element vehicle models created under the ACAP program are in the public domain, for the purpose of encouraging safety research by others in both the public and private sectors.

For more information about this topic:

• Federal Outdoor Impact Laboratory
• FHWA's Office of Safety Roadway Departure
• National Crash Analysis Center