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Curbing Highway Fatalities

"Using a nonlinear dynamic finite-element program the team models vehicles, curbs and guardrails and performs virtual crash tests."

By Nancy Langmeyer

Each year, about 300 people die as a result of collisions with guardrails. According to Malcolm Ray, the culprits in many of these fatalities are not the guardrails, themselves, but adjacent curbs that can cause drivers to lose control of their vehicles, and cause vehicles to roll over or even vault over the guardrails.

Since the curbs are necessary to channel rainwater and prevent erosion, the solution is not to remove them, but to find ways to make them work in harmony with guardrails and other highway barriers, notes Ray, Ralph H. White Family Distinguished Professor in WPI's Civil and Environmental Engineering Department.

In research sponsored by the National Cooperative Highway Research Program, the research arm of the American Association of State Highway and Transportation Officials (AASHTO), with additional support from the Federal Highway Admin- istration, Ray is determining the optimal combination of curb and guardrail designs and configurations, so each can do its intended job without endangering motorists.

Traditionally, research on highway barriers has required full-scale crash testing, which can be expensive (about $35,000 for a single test). Ray and his research team complete most of their testing with sophisticated computer models. Using a nonlinear dynamic finite-element program called LS-DYNA, the team models vehicles, curbs and guardrails and performs virtual crash tests. In a fraction of the time it takes to do real tests, they can study multiple combinations of curbs, guardrails, impact angles and speeds.

WPI is a leader among the handful of laboratories around the world that can conduct this type of analysis. In fact, the university is one of just three sites in the United States designated by the Federal Highway Administration as centers of excellence in finite-element analysis modeling. Ray says WPI will also become a leader in education in this field this fall when it inaugurates the interdisciplinary Master of Science in Impact Engineering program, the first of its kind in the world.

The results of Ray's research will be included in future updates of AASHTO's Policy on Geometric Design of Highways and Streets and The Roadside Design Guide. These guidelines for designing safe highways are the basis for design standards in use in all 50 states. Ray says it is gratifying to see his work put to use so quickly to have a real impact on safety.

"We take real problems and come up with real solutions that are needed right away," he says. "For instance, the state of Pennsylvania came to us when it found that it had a system of guardrails that no longer met federal guidelines. Within a year of our first involvement, an improved guardrail was being installed on the Pennsylvania highways. Not only do those guardrails meet federal standards, but as a result of their installation, there will be fewer fatal crashes."

In the sequence above, from a computer simulation, a 2000-kilogram pickup truck traveling at 100 kilometers per hour collides with a guardrail and a 100-millimeter curb at a 25-degree angle. Through studies like this, completed with sophisticated finite-element analysis software, Malcolm Ray and his team are searching for combinations of guardrail and curb designs that will lower the incidence of fatal accidents on America's highways.

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Last modified: Jun 20, 2008, 15:05 EDT
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