Vehicles of different shapes and sizes are increasingly compatible. Recent changes in SUVs and cars have made crashes involving the two vehicle types less dangerous to car occupants than they used to be. A decade ago, SUVs and pickups were much more likely than cars or minivans of the same weight to be involved in crashes that killed occupants of other cars or minivans (see Status Report special issue: incompatibility, April 26, 2003). Nowadays, the threat posed by SUVs isn't much bigger than cars of the same weight, and even pickups aren't nearly the danger to people in cars that they were before, a new Institute study finds.
The researchers attribute much of this change to two things: improved crash protection in the cars and minivans, thanks to side airbags and stronger structures, and newer designs of SUVs and pickups that make the energy-absorbing structures of their front ends line up with those of cars. The more compatible designs are the result of efforts by automakers, the government, and the Institute to address the problem of mismatched vehicles.
The analysis of car/minivan occupant deaths in 2008-09 is the latest piece of Institute research showing that SUVs aren't the safety concern they once were. Recently calculated driver death rates for 2005-08 models show that drivers of SUVs are among the least likely to die in a crash. That change is due largely to electronic stability control (ESC), which has been standard on most SUVs in recent years and is required on all passenger vehicles beginning with 2012 models. ESC has greatly reduced the tendency of SUVs to roll over (see "Dying in a crash," June 9, 2011). It also lowers the chances of crashes with other vehicles.
"ESC has made SUVs less likely to crash, while more compatible front-end designs have helped to reduce the risk they pose to people in cars when crashes do occur," says Joe Nolan, the Institute's chief administrative officer and a co-author of the new study. "Whether you're in an SUV or just sharing the road with one, recent improvements to these vehicles are making you safer."
Deaths in 2-vehicle crashes
Institute researchers measured the risk posed to other vehicles by 1-4-year-old SUVs in 2000-01 and 2008-09 by looking at the number of car and minivan occupants killed in 2-vehicle crashes with those SUVs per million registered vehicle years. (A registered vehicle year is 1 vehicle registered for 1 year, 2 for 6 months, etc.) The same calculations were done for 1-4-year-old pickups and 1-4-year-old cars and minivans. The cars or minivans in which people were killed, known as crash partner vehicles, could be of any age, size, and weight. Data on crash deaths are from the federal Fatality Analysis Reporting System, and registration information is from R.L. Polk & Co.
In both 2000-01 and 2008-09, the rate of crash partner deaths generally went up as vehicle weight increased. This isn't surprising since vehicle weight is a key factor in the outcome of crashes. However, in the first period there was significant variation within each weight category. SUVs were more deadly to people in other vehicles than cars of the same weight, and pickups were more deadly than SUVs.
From 2000-01 to 2008-09, the rate of crash partner deaths fell for all weight categories of all 3 types of vehicles, except the relatively small group of cars and minivans weighing 4,500-4,999 pounds. Improvements in occupant protection in the crash partner cars and minivans helped lower the number of deaths. The spread of ESC, as well as changes in travel patterns due to the sluggish economy and high gas prices, likely also contributed to this decline.
Beyond the overall decrease, crash partner death rates for pickups, SUVs, and cars/minivans weren't as far apart in 2008-09 as they were in 2000-01. In fact, among 1-4-year-old vehicles in any given weight category, an SUV usually posed no more risk to people in a car or minivan than another car or minivan. That wasn't quite true for pickups, which still fatally injured people in cars and minivans at a higher rate, particularly in frontal crashes.
Crash partner deaths for 1-4-year-old vehicles per million registered vehicle years
"Pickups lagged behind other vehicles in getting ESC, and designs of some top-selling models were slow to change. Those facts help explain why the numbers didn't improve as much for pickups as for SUVs," Nolan says. "Also, pickups often carry loads, so the trucks in these crashes could be a good deal heavier than their curb weights."
These results don't contradict the basic physics of crashes. Size and weight still are key, and a small, lightweight vehicle is going to fare worse than a big, heavy vehicle in a crash. In general, SUVs and pickups are heavier than cars, so in that sense different types of vehicles always will be mismatched. But the study shows that, beyond weight, differences in vehicle styles don't have to be a safety problem.
Design changes that improved compatibility came out of a series of meetings held in 2003 after the National Highway Traffic Safety Administration asked automakers to address the issue amid concern about the changing vehicle mix on U.S. roads. The Alliance of Automobile Manufacturers, the Association of Global Automakers, and the Institute led the working groups. Participating automakers included BMW, Chrysler, Ford, General Motors, Honda, Hyundai, Isuzu, Kia, Mazda, Mercedes-Benz, Mitsubishi, Nissan, Subaru, Suzuki, Toyota, and Volkswagen. The manufacturers agreed to build more compatible front ends on SUVs and pickups to reduce the likelihood that these vehicles would override cars in collisions. Better alignment allows both vehicles' front ends to manage the crash energy, keeping it away from the occupant compartments.
These changes made a difference. In an earlier study, the Institute compared crash data for vehicles that complied with the voluntary agreement versus vehicles that didn't, finding that the changes reduced fatality risk for belted car drivers in crashes with SUVs 18-21 percent and 9-19 percent for car drivers in crashes with pickups (see "Automakers' efforts reduce mismatch between cars and light trucks," Jan. 28, 2006).
Although the modifications were meant to address frontal crashes, they also reduced fatality risk for drivers of cars struck in the side by SUVs by 47-48 percent and for those struck by pickups by a more modest 1-9 percent. Cars can withstand side crashes better when they're struck in the door sill area than when the impact is higher.
The automakers also pledged to strengthen head protection in all vehicles to improve outcomes when a pickup or SUV strikes another vehicle in the side. The agreement coincided with consumer pressure for better side protection stemming from the Institute's crash tests. Manufacturers met both challenges by installing more head-protecting side airbags.
The deadline for compatibility changes was September 2009, but many of the 2004-08 models in the current study already complied. Among 2004 models, 54 percent of SUVs and pickups met the front-end requirements. In 2007, 81 percent did.