Rear underrun crashes involving heavy vehicles with rear overhangs represent the most extreme examples of incompatibility between heavy vehicles and passenger cars. This type of crash often causes severe or fatal injuries to car occupants.

This paper describes the development of a threedimensional MADYMO model simulating a car crashing first at 48km/h and then at 75 km/h into the rear of a truck with an energy-absorbing rear underrun barrier attached. The underrun barrier was designed to absorb part of the impact energy of the car and hence reduce the injuries of the car occupants. The collision was simulated in order to aid the design and analysis of energy-absorbing truck underrun barrier systems.

A Hybrid III 50th percentile male dummy was used to model the driver and to calculate the Head Injury Criterion (HIC), head resultant deceleration and the chest resultant deceleration. The vehicle deceleration pulse during impact, resultant forces in the barrier and in the tube-in-tube struts as well as the injury outcomes from the dummy, were first validated using laboratory crash tests carried out at a speed of 48 km/h [Rechnitzer et al 1996]. This model was then used to predict the vehicle deceleration, strut forces and injury outcomes for the 75-km/h crash. The simulation results show fairly good agreement with the crash test indicating that such models can be used at a relatively low cost to design crashworthy structures and investigate such injury prevention counter measures