A recent study by the Insurance Institute for Highway Safety in the USA shows that when it comes to occupant vehicle safety the notion that big is always better does not always ring true. 

The Insurance Institute for Highway Safety (IIHS) is the US equivalent of Thatcham and has found that adding more weight to a vehicle above the fleet average has little additional safety benefit for occupants, but adds significantly to the risks to other road users. 

IIHS President David Harkey said, “For American drivers, the conventional wisdom is that if bigger is safer, even bigger must be safer still. These results show that isn’t true today. Not for people in other cars and not for the occupants of the large vehicles themselves.”

The study looked at recent crash stats in the US. It found 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 cars crashed into by one. 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.

Sam Monfort, a senior statistician at IIHS and lead author of the study commented, “What this analysis shows is that choosing an extra-heavy vehicle doesn’t make you any safer, but it makes you a bigger danger to other people.”