IIHS: Larger Vehicles Offer Minimal Safety Benefits, But Pose Other Dangers

Bigger vehicles may be safer, but only marginally, and they carry risks to other vehicles on the road, new research from the Insurance Institute for Highway Safety shows.

For vehicles weighing less than fleet average, the risk that occupants will be killed in a crash decreases substantially for every 500 pounds of additional weight. However, those benefits top out quickly, the IIHS research shows.

Adding 500 pounds to a lighter-than-average vehicle poses little to no increased risk to people in other vehicles, yet the same weight increase for a heavier-than-average vehicle heightens the danger to people in other vehicles, according to the findings.

IIHS researchers examined two-vehicle crashes between one- and four-year-old cars, SUVs and pickups from 2011 to 2016 and 2017 to 2022, calculating driver death rates for vehicles and their crash partners per million registered vehicles.

The research found that compatibility across vehicle types has continued to improve. For many years, SUVs and pickups posed an outsize threat to people in cars, in part because their force-absorbing structures were not aligned. When an SUV or pickup struck a car, it bypassed the car’s crumple zone and rode up over the hood of the smaller vehicle.

Beginning in 2009, automakers changed the front ends of SUVs and pickups to make them align better with cars’ energy-absorbing structures. They also strengthened the structures of their cars and added side airbags to all varieties of vehicles to protect occupants in T-bone crashes. Since, both SUVs and pickups have become less dangerous to people, according to IIHS.

For years before the changes were made, car occupants were 90% more likely to die in crashes with SUVs weighing more than 5,000 pounds as in crashes with other cars. In contrast, between 2017 and 2022, those heavy SUVs were only 20% more likely than cars to result in car-partner fatalities, according to IIHS.

The average weight of passenger vehicles in the study sample was 4,000 pounds. For cars below that average, every additional 500 pounds in curb weight reduced the driver death rate by 17 deaths per million registered vehicle years, while only increasing the death rate for crash-partner cars by one, according to the research.

In contrast, for pickups above the average weight, every additional 500 pounds only reduced the driver death rate by one but increased the death rate for crash-partner cars by seven.

Changes in vehicle weights accounted for some of the improvements in compatibility as well as the continued gap between SUVs and pickups. The weight of the average U.S. car increased to 3,308 pounds in 2017 to 2022, bringing the category closer to the 4,000-pound all-vehicle average. As that was happening, the portion of SUVs weighing more than 5,000 pounds fell from nearly 11% of all late-model SUVs in 2011 to 2016 to 7.4% in 2017 to 2022. In contrast, pickups got larger. The proportion weighing more than 4,000 pounds increased to 97% of late-model pickups in 2017-22 from 91% in the earlier period, according to IIHS.