An examination of the role that vehicles play in maintaining occupant safety can be instructive in determining the potential impact of sharp weight reductions. The vehicle must do the following:
Aid the driver in keeping the vehicle on the roadway. If the vehicle leaves the roadway, avoid a rollover. In a crash, absorb crash forces in such a way that no intrusion of the passenger compartment occurs. Also, control the deceleration of the vehicle so that it occurs in as uniform a way as possible, over as long a crush distance84 as possible.
Finally, prevent the passenger from crashing against interior surfaces and/or minimize damage if he does, prevent ejection of the passenger, and control the way deceleration forces affect the passenger. Weight plays a different role in each of these vehicle tasks.
Weight may be protective in keeping vehicles from being adversely affected by crosswinds, but directional stability and handling are affected far more by wheelbase, suspension, and steering system design, tire design and maintenance, and other no weight-related factors.
Rollover can be weight-related because in lightweight cars, the payload will have a greater effect on the height of the center-of-gravity than it will in heavier cars. This effect maybe positive or negative depending on vehicle design, and specifically on the location of the payload vis-à-vis the location of the empty vehicle’s center-of-gravity.
However, rollover propensity is primarily a function of wheelbase, track width, suspension design, and overall vehicle design; a small increase in track width can compensate for any increase in rollover propensity that might occur from “light weighting” a vehicle.