Influence of a Truck Side Under-Ride Guard Height on Cabin Intrusion and Occupant Injury Potential of a Small Car in Car/Large-Truck Side Crashes

In car/large truck collisions, the size, weight, and stiffness mismatch results in a much larger structural deformation of the car compared to that of the truck, and larger potential for car occupants injuries. This is further aggravated when the passenger vehicle trends beneath the rear or side of the taller truck. In the US, under-ride guards are required only for the rears of large trucks, although the review of fatal truck-car crashes in the NCSS/CDS indicates that fatal under-ride crashes involving the sides of large trucks are almost as common as fatal rear under-ride crashes. A methodology using validated finite element models of a passenger car and a truck is utilized in this study to quantify the influence of a side guard attached to a large truck in reducing the intrusion of the car and thus reducing the injury sustained by the occupants of a car in a side crash. A formulation is proposed based on a normalized passenger compartment intrusion and its relation to the occupant injury potential. The transmitted deceleration severity and the occupant compartment intrusion are evaluated for the car impacting a rigid under-ride guard. A NHTSA under-ride test is simulated first for model validation. Once model validation is conducted for a specific guard design, further simulations are conducted at the speed range of 30 to 50 mph and for 90 and 45-degree impact angles. The results from a parametric study are used to identify the critical guard height resulting in severe cabin deceleration and compartment intrusion of the small car. This study quantifies the vulnerability of car occupants in truck side under-ride crashes and the effectiveness of side guard at different ground heights in reducing the injury potential to car occupants.