Small cars still have higher driver death rates, IIHS study shows

Small cars have come an extremely long way in terms of occupant safety in a crash, but overcoming the momentum of a large vehicle is not easy.


Honda via IIHS

It doesn’t take more than a brain cell or two to jell with the idea that small cars crashing into large cars won’t turn out well for the small cars, despite decades of active and passive safety advancements. Now, a recent Insurance Institute for Highway Safety study puts some more concrete figures behind the safety of small cars in the modern era.

The IIHS this week released a study looking at recent death rates of vehicle drivers. The study found that compact and subcompact vehicles comprised 75% of models with the highest driver death rates across the 2017 model year. The data was broken down into driver deaths per million registration years, as well as driver deaths per 10 billion miles driven. This study only looked at driver death rates, as all cars contain drivers but may not contain additional passengers, in order to keep the data as steady as possible.

“Smaller vehicles offer less protection for the driver in crashes, and their lighter mass means that they take the brunt of collisions with larger vehicles,” says Joe Nolan, IIHS senior vice president of vehicle research. Momentum is the issue here: You determine momentum by multiplying mass and velocity, so more mass means more momentum, which means more energy to impart in a collision.

As you might expect, the study also points out that luxury SUVs, which tend to be hulking behemoths, comprise half of the 2017 models with the lowest death rates. The IIHS points to a few factors here in addition to mass, such as the prevalence of standard safety systems on higher-cost vehicles.

But the data alone doesn’t paint the whole picture. The IIHS admits as much in the release accompanying the study. By measuring the death rates per miles driven, the group was able to highlight additional reasons why the data shows what it does. Take sports cars, for example: These vehicles are driven less often than, say, a family minivan, so looking at the data in terms of miles driven means sports cars show a higher death rate. Trucks, as the IIHS notes, are driven to the ends of the earth and back, which means they get a lower death rate per billion miles driven.

There are also some unusual exceptions in the IIHS study. Using both measurement metrics, the IIHS found two cars with extremely low rates of driver death: The Volkswagen Golf and Nissan Leaf both have driver-death figures well below their segment averages. While the Leaf might highlight the intricacies of how consumers treat electric vehicles, the IIHS did not ascribe any specific reasoning to why these two cars are exceptions, just that they are.

So, what’s the takeaway here? The IIHS isn’t trying to sell you on a larger car here — ever-embiggening vehicles means someone is almost always going to have the short end of the stick in a collision, and building every car to be the size of a tractor-trailer will have ramifications on everything from the window sticker to fill-up costs. The only thing the IIHS cares about is automakers building the safest vehicles possible, so if anything, this study should give automakers ideas about how to better their small cars while helping consumers make informed purchases.

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