The University Record, August 12, 2002

Heavier cars not necessarily safer

By Judy Steeh

News and Information Services

A U-M physicist and a research scientist are questioning the belief that bigger and heavier vehicles are automatically safer than other cars and trucks.

U-M physicist Marc Ross and Tom Wenzel, a research scientist at Lawrence Berkeley National Laboratory (LBNL), recently released a report that shows vehicle quality is a better predictor of safety—both for the driver of the car in question and for other drivers—than weight.

“Safety is a challenging concept. It includes the design of the car itself, driver demographics and behavior, the kinds of roads, the time of day—a whole host of factors,” Ross said. “What we need to do is move away from the idea that bigger and heavier vehicles are automatically safer.”

Recent Senate hearings on Corporate Average Fuel Economy standards focused on the increased risk Americans would face if they had to give up their SUVs for vehicles that weigh less.

“We set out to see whether that risk is real, whether SUVs really are safer than cars,” Ross said. “The answer, by and large, is no.”

The first major result Ross and Wenzel found is that SUVs are no safer for their drivers than cars. Popular midsize cars, minivans and import luxury cars have the safest records, while SUVs are about as risky as the average midsize or large car, and are no safer than many compact and subcompact models. The researchers defined “risk” as the number of deaths per year per million vehicles.

Other studies have not considered combined risk, which looks at the risk to the driver of the model in question and the risk to drivers of all other vehicles involved in crashes with the model in question. This study found that, when measuring the combined risk, most cars are safer than SUVs, while pickup trucks are much less safe than all other vehicles.

“Clearly the characteristics of the drivers of certain types of vehicles also have a strong effect on their safety,” Ross said. “However, it is not clear exactly what that effect is, and the age and sex of drivers do not fully explain these results.”