Researchers Say Underride Guards Need Optimum Height

Truck underride guards are most effective when installed 16 inches from the ground, a university test recently found.

Researchers from Penn State University tested the rear guards, which are designed to keep a car from sliding underneath a trailer or truck in a rear-end collision. The test concluded that underride guards are less effective if lower or higher than 16 inches from the ground.

National Highway Transportation Safety Administration regulations require a maximum ground clearance of 22 inches, but have not set a minimum level for underride guards on new trucks.

Results of the test were presented Nov. 17 at the American Society of Mechanical Engineer’s International Mechanical Engineering Congress and R & D Expo in Washington, D.C.

Researchers tested collisions at 30 and 40 miles per hour. Underride guards designed with diagonal struts also help reduce vehicle penetration.

Researchers said the test should be evaluated further with different vehicles and various bumper heights.

Crash animation may be downloaded at