Development of a New Guardrail System

Abstract

The W-beam guardrail system has been the standard in the United States since the late 1950s and has proved to perform reasonably well under most impact conditions. However, in recent years the vehicle fleet has changed to include a relatively large percentage of light trucks, such as pickups, vans, and sport-utility vehicles. These vehicles have a higher center of mass and bumper mounting height than conventional automobiles and have been shown to have higher rollover and injury rates during guardrail accidents than conventional automobiles. Standard W-beam guardrails were not designed to capture the bumper of many of these vehicles. In recognition of the potential safety problems associated with light-truck accidents, safety performance standards were recently changed with the publication of NCHRP Report 350, Recommended Procedures for the Safety Performance Evaluation of Highway Features. These performance standards require all new safety hardware to be tested with a full-size three-quarter-ton pickup to ensure acceptable performance for most vehicles in the light-truck category. In recognition of this, a guardrail system capable of capturing and redirecting a larger range of vehicle types and sizes was developed. A new guardrail system, called the Buffalo Rail, was designed with a new cross-sectional shape with an effective depth of 311 mm (compared to 194 mm for the W-beam), a rail thickness of 13 gauge, and a post spacing of 2500 mm. The safety performance of the Buffalo Rail was found to be acceptable according to the procedures and criteria recommended for the three-quarter-ton pickup truck at Test Level 3 in NCHRP Report 350.