SUVs, Crossovers and Safety

SUV safety, once a key concern for the segment when it was booming in the 1990s, has made real strides in recent years. The Insurance Institute for Highway Safety reported in June 2011 that SUVs (including crossovers) are now safer than cars, even when comparing vehicles of similar weight. Real-world fatality data for 2005-2008 models reveal 28 driver deaths per million registered SUVs. There were 56 car driver deaths and 52 pickup driver deaths per million for the same period. Minivans were the safest with 25 driver deaths per million registered vehicles.

So what's changed? SUVs' rollover propensity. The vehicles are heavier and ride higher than cars, and this is always an advantage in a crash, all other things being equal. In the early days of SUVs, their rollover propensity wasn't an equal factor, and because rollovers are more frequently fatal than are other accident types, SUVs were more deadly despite their other advantages.

One major improvement is the adoption of electronic stability systems, which can prevent some of the conditions that lead to rollovers. Some models, mainly from Ford and its former divisions like Volvo and Land Rover, can detect a rollover in progress and intervene to stop it. Automakers deserve the credit because they proliferated the safety feature in SUVs long before the U.S. government mandated its inclusion in all vehicles, regardless of size, for the 2012 model year.

There's more to it, though. Automakers have changed SUV design markedly, lowering the center of gravity and making SUVs inherently more stable. As the SUV/crossover market has exploded, it's come mainly from car-based models -- and quite a few vehicles that are little more than cars in SUV guise. As a whole, this approach is more stable than the old body-on-frame truck-based design.

Of the 2012 SUVs and crossovers rated by the National Highway Traffic Safety Administration as of this writing, there are only a few car-based models with rollover ratings of three stars instead of four (five is best), including the Ford Escape (plus its sister models, the Mercury Mariner and Mazda Tribute). All other three-star-rated 2012 SUVs are the heavier-duty, truck-based type.

One of the truck-based SUVs currently rated gets four stars: the hulking Toyota Sequoia. Four-wheel-drive versions of the Ford Expedition, Lincoln Navigator and Jeep Grand Cherokee also rate four stars, but the rear-wheel-drive models get three stars. No SUV has a five-star rollover rating.

Safety Features for SUVs

Some desirable safety features for SUVs and crossovers are the same as those for any vehicle: antilock brakes, three-point (lap-and-shoulder) seat belts and head restraints in all seating positions, multistage frontal airbags, and occupant classification in the front passenger seat, which determines the occupant's weight (and thus size) and fires the airbag at one of two or more levels of intensity.

Three features are especially useful in SUVs and crossovers, and one you should avoid, if safety is a concern:

1. Electronic stability system: Electronic stability systems can limit acceleration and apply any of the antilock brakes to keep you on course if you start to lose control. It doesn't prevent a rollover, but it's quite effective at preventing conditions that can lead to one. For this reason, the industry was already on its way toward making the feature standard equipment on SUVs before the NHTSA mandated it on all cars and light trucks for the 2012 model year. If you're shopping for a used SUV, make sure it has a stability system, which is marketed under names like ESP, StabiliTrak, DSTC, VSC and VDC.

What to look for: Don't confuse this feature with simple traction control (also sold under acronym names), which only prevents wheelspin upon acceleration. Be sure that an electronic stability system is what you're getting.

2. Side curtain airbags: This type of airbag deploys downward from the ceiling to cover some or all side windows upon side impact. One could argue that this type of airbag is less important on taller vehicles because other tall vehicles are likely to strike your SUV's doorsills or doors, which are built to absorb energy. (A car, on the other hand, would have only windows and narrow pillars to protect its occupants from a collision with a truck.) But side curtain airbags in some models can serve another purpose: In the event of a rollover, they protect occupants and help keep them inside the vehicle, staying inflated long enough for several rolls. Occupant ejection — not roof crush strength — is the main cause of deaths in rollover accidents.

What to look for: Just having side curtain airbags isn't enough. Make sure they're designed to deploy in a rollover. Also favor systems that cover all rows of seats. Not all three-row vehicles have protection for the third row.

3. Rollover prevention:
Something of a holy grail among SUV safety features, a rollover prevention or avoidance system actually senses an impending rollover and triggers the electronic stability system to forestall it. (Stability systems alone can only diminish the chance of tipping up on two wheels to begin with.) The Volvo XC90 was the first vehicle to offer this feature, which the automaker calls Roll Stability Control. Once a Ford division, Volvo shared the RSC system with other Ford vehicles, including the Lincoln Navigator. It is still available on some models from Land Rover, which Ford owned until 2008.

What to look for: Check our model reports to find which Ford, Mercury, Lincoln and Land Rover products offer RSC.

4. Aftermarket wheel and tire "upgrades": This is the feature you should avoid if you care about safety and rollover prevention. This will be unpopular with style-conscious buyers, but it must be said: An increasing number of vehicle owners are customizing their vehicles (wheels and tires being the most common upgrade) in complete ignorance of the effects on safety. To put it plainly, vehicles are designed to work as a system. Change any part, and there are consequences. Wheel and tire combinations that are larger, heavier and/or have greater traction are likely to diminish an SUV's safety. Larger diameters foil antilock brakes and stability systems, and can compromise braking. Heavier weight affects the suspension's ability to keep the tire on the road and again affects braking. Tires with greater grip can increase the chance of rollover. If that doesn't convince you, bear in mind that the manufacturer has little or no responsibility for your safety if you've modified the vehicle mechanically. In short, your next of kin would have a tough time in court.

What to look for: If you must customize your vehicle, your best bet is to stick with the options developed by the manufacturer, of which there are now more choices than ever. If you insist on aftermarket equipment, don't go to extremes. Keep the outside diameter of the tire the same, don't increase the wheel diameter too much and think twice about putting significantly different tires on your ride. Believe it or not, the people who engineered your vehicle — as a unit — really know what they're doing.

Protecting Those Outside Your Vehicle

While SUVs and crossovers are getting better at protecting their occupants, there's also the issue of protecting the occupants of the smaller vehicles with which they might collide. Aside from the weight issue, it's a matter of geometry: A truck can ride up over the most robust part of a car's frame structure, bypassing its crumple zone and plowing into its cabin. Thankfully, there's evidence that SUVs are becoming less deadly in this regard. Many manufacturers have worked since 2003 to make SUVs more compatible in crashes with smaller vehicles by lowering their frames to engage a car's crumple zones.

IIHS cross-referenced a list of such SUVs with fatality data from the past few years and found that the fatality risk for a belted car driver was as much as 21 percent lower when crashing head-on with a compatible SUV than with a conventional one. (There's practically no change for unbelted drivers.) The side-impact results are more dramatic: a nearly 50 percent decline in car occupant fatality risk when hit by a compliant SUV.

There are also features that can help protect pedestrians behind vehicles — a significant problem in SUVs that sit high and have large blind spots. One is a sonar-based "park assist" system that sounds beeps of increasing frequency as the rear bumper nears an obstacle or person. A newer feature, the backup camera, shows a wide-angle view behind the vehicle on a screen when the vehicle's transmission is in Reverse. This feature mainly comes along with expensive optional navigation systems, but in the past couple of years, the feature has proliferated as a stand-alone option with separate, smaller displays in dashboards and rearview mirrors.

Young Drivers and SUVs

Speaking generally, SUVs aren't the best choice for young or inexperienced drivers. The threat of rollovers still looms, and when you combine that with the fact that single-vehicle accidents are most common among young drivers, you can see the danger. The lesson that too few drivers learn is that trucks don't handle or stop like cars do. They're generally not as nimble, and they don't stop as quickly. A young driver who takes a freeway off-ramp at 50 mph in a sports car might continue unscathed. One who does the same in a family sedan might slide off into the weeds or something less forgiving. One who tries it in an SUV is more likely to roll over. Simply put, SUVs are best for drivers who have more self-control than teenagers do.

© 09/12/2011