A recent study from the Insurance Institute for Highway Safety (IIHS) challenges the common belief that larger, heavier vehicles provide better protection in crashes. While many assume that driving an SUV or truck guarantees superior safety, data reveals that weight alone doesn’t significantly reduce fatalities for occupants—but it does increase the danger for others on the road.
The Weight Factor in Crash Safety
The IIHS analyzed crash data from vehicles manufactured between 2017 and 2022, determining that the average curb weight of cars in the study was 4,000 pounds. For vehicles exceeding this weight, every additional 500 pounds resulted in only one fewer death per million registered vehicle years—an insignificant improvement. However, that same increase in weight led to up to seven additional deaths for occupants of lighter vehicles involved in crashes with heavier SUVs and trucks.
Conversely, lighter cars and SUVs—those weighing under 4,000 pounds—could benefit from additional weight. Increasing their curb weight to approach the 4,000-pound average correlated with a reduction of 17 deaths per million in car-to-car crashes and 13 fewer deaths in SUV-to-car collisions. Essentially, staying close to the average vehicle weight enhances overall safety, rather than opting for an excessively heavy model.
The Myth of “Bigger Equals Safer”
“There’s nothing magical about 4,000 pounds except that it’s the average weight,” explained Sam Monfort, lead author of the study. “Vehicles heavier than average tend to crash into lighter vehicles, making those crashes more deadly. This analysis shows that choosing an extra-heavy vehicle doesn’t make you safer, but it does increase the risk for others.”
Historically, heavier SUVs and trucks have posed a significant danger to smaller vehicles. Between 2011 and 2016, occupants of smaller cars were 90% more likely to die in a crash involving an SUV over 5,000 pounds. However, from 2017 to 2022, that risk dropped to 20%, thanks to automakers and IIHS aligning crash structures between different vehicle types.
A Changing Perspective on Vehicle Safety
IIHS President David Harkey reinforced the study’s key finding: “For American drivers, the conventional wisdom is that if bigger is safer, then even bigger must be safer still. These results show that isn’t true—not for people in smaller cars and, crucially, not for occupants of the large vehicles themselves.”
The study highlights the need for balanced vehicle design and safety standards, rather than an assumption that size alone dictates survival in a crash. While larger vehicles may provide some advantage, they also pose greater risks to others, underscoring the importance of engineering advancements in crash protection for all road users.
