An Approach to Developing Underride Guard Requirements for Improved Occupant Protection

Initial efforts for developing regulations for improved rear underride protection focused on very high strength (rigid) structures with low ground clearance. To determine optimal performance characteristics for guard structures, a comparative engineering analysis was performed using a car crash simulation model with a variety of guard, force-deformation characteristics. From this analysis the risk of injury to occupants of passenger cars was determined based on excessive underride (decapitation potential), and collision forces imparted to the occupant. Variables in the analysis included collision speed, car size, occupant free travel distance, and the rear wheel position of the heavy vehicle, as well as the various force-deformation characteristics representing the different types of underride guard systems.