A united effort by state and federal agencies to save more lives.

American Association of State Highway and Transportation Officials
444 N Capitol St NW
Suite 249
Washington DC, 20001

Governors Highway Safety Association

Federal Highway Administration

National Highway Traffic Safety Administration

Transportation Research Board of The National Academies

National Cooperative Highway Research Program

Implementation Guides

« Back to Implementation Guides

Volume 07: A Guide for Reducing Collisions on Horizontal Curves

Making Curves Safer to Negotiate

Nearly 25 percent of the people who die each year on the nation’s roadways are killed in motor vehicle crashes occurring at curves. About 75 percent of all fatal crashes occur in rural areas, and more than 70 percent on two-lane secondary highways, many of which are local roads.


The average crash rate for horizontal curves is about three times that for highway tangents. Statistical analyses show that 76 percent of curve-related fatal crashes involve single vehicles leaving the roadway (ROR) and striking fixed objects or overturning. Another 11 percent are head-on crashes.


In light of these facts, the main objectives for improving safety at horizontal curves are: Reducing the likelihood of a vehicle leaving its lane, crossing the roadway centerline, or leaving the roadway at a horizontal curve; and minimizing the adverse consequences of leaving the roadway at a horizontal curve.

Download this guide: http://trb.org/publications/nchrp/nchrp_rpt_500v7.pdf

NCHRP Report 500-7

Horizontal Curves


Even though detecting safety problems on curves can be difficult, once they are identified this guide provides a range of safety improvements that can be considered. This guide for Reducing Collisions on Horizontal Curves lists a range of strategies and countermeasures, ranging from low-cost, short-term treatments to high-cost, long-term solutions.

Download the guide in PDF

View the Guide and Appendices in HTML

Order a printed copy

Related publications


Horizontal Curves One Pager


Self Assessment Tool


Integrated Safety Management Process