EFFECTS OF GEOMETRY AND STIFFNESS ON THE FRONTAL COMPATIBILITY OF UTILITY VEHICLES

The issue of vehicle incompatibility, especially between passenger cars and utility vehicles/pickup trucks, has received a lot of attention in recent years. Real-world crash data show that occupants of cars are much more likely to be injured in frontal crashes with utility vehicles and pickup trucks than with other passenger cars, even after controlling for vehicle mass. Factors in addition to mass that can influence compatibility are stiffness and geometry. In this paper, the effects of these factors on occupant injury measures and vehicle deformation patterns are examined. The Insurance Institute for Highway Safety conducted a series of car-to-utility-vehicle frontal offset tests with the Ford Taurus as a common collision partner. To vary stiffness, the Taurus collided with either a Mercedes ML320 or a relatively stiffer Isuzu Rodeo. To vary geometry, the test matrix included an ML320 at normal ride height, a Rodeo at normal ride height, an ML320 lowered 9 cm so the frame rails matched the ride height of the normal Rodeo, and a Rodeo raised 9 cm to match the ride height of the normal ML320. In each test, both vehicles were traveling at 48 km/h (30 mi/h). A Hybrid III 50th percentile male dummy was seated in the driver’s seat of each vehicle. Vehicle deformation patterns, dummy injury measures, and vehicle accelerations were recorded and compared. Results indicated that, despite its lesser stiffness, the normally higher ride height of the ML320 produced a less ‘compatible’ crash than the Rodeo, whose front end is stiffer but normally lower. The benefits of lesser front-end stiffness were smaller and only apparent in comparisons of tests at a common ride height. These results indicate that there is little benefit of reduced utility vehicle stiffness without good geometrical alignment of vehicles’ front structures.