With their higher center of gravity, SUVs are more at risk of rollover accidents than sedans or coupes. Swinging a heavy SUV hard in one direction to avoid something that appears on the road ahead—like a moose—is easy even with the most massive SUVs. Power steering lets you do it with a finger. But you may put the vehicle’s center of gravity past its outside wheels in a tight turn. Suddenly, you are driving on two wheels. Decrease the radius or enter the turn with a high enough velocity and you will roll the vehicle over, possibly multiple times. If you hit the moose, you may set off the vehicle’s airbags, but they will deflate after a second, leaving you with only a seatbelt to keep your body from bouncing around the vehicle or flying out of it. Then it is up to the vehicle’s support pillars to keep the roof from collapsing.
It was a rollover that killed Seymour Cray, founder of Cray computers and the father of supercomputers, in a case that is often used for finite element analysis (FEA) of crashes. The 70-year-old Cray was hit while driving his SUV, which rolled over three times. He was wearing a seatbelt, but still the accident broke his neck and he died of head injuries two weeks later.
Why Moose?
Moose like other members of the deer family have spindly legs and a high center of gravity. A full-grown moose can weigh almost as ton. Its center of gravity is eye level to a motorist. Hitting the animal head on will bring the moose over the vehicle’s hood and into the passenger compartment. There is a good chance that no one will survive the accident—including the moose.
Moose are most commonly found as you get into the Northern Latitudes, in Northern New England and Alaska in the US, Canada, the Scandinavian countries and Russia. Swedish automakers Volvo and Saab have conducted moose tests for years. While the evasive maneuver is done with cones, the Swedish National Road and Transport Research Institute has developed a moose dummy to simulate the damage caused by the real animal.
Risk of Rollovers in SUVs
The Ford Explorer, created after Ford, in a hurry to cash in on the SUV market, fashioned a family vehicle from a pickup truck. Accident statistics from Safety Research & Strategies revealed that one in every 2,700 Ford Explorers built between 1990 and 2001 rolled over and killed at least one person in the vehicle.
It was an improvement over the previous Ford SUV, the Ford Bronco II, which was killing one person for every 500 Broncos. A Frontline documentary, “Rollover,” has a Ford engineer saying that the company knew the SUV was killing people in rollovers more often than other SUVs and that the problem had been discovered in road tests prior to the release of the Bronco II. Ford engineers recommended lowering the vehicle’s center of gravity and widening its track by two inches to increase its stability, but those changes would have delayed production and the vehicle’s release date. Ford declined to make the recommended changes.
Most SUVs are sheet metal bodies bolted on to truck chassis, missing the rigidity of the monocoque or semi-monocoque construction that is common to cars. That combined with their extra mass makes them more likely to crush their occupants in rollovers. Rollovers account for only 3 percent of crashes but more than a third of occupant deaths, according to a 2005 Wall Street Journal report.
SUV drivers love the view from the top, sitting high and being able to see over cars and farther down the road. Yet that sensation may be causing them to drive faster. Being higher off the ground makes people feel like they are going slower. A person going 60 mph in an SUV would have a perceived speed of 40 mph, says Ron Noel, assistant professor of psychology at Rensselaer Polytechnic Institute. As a result, they could take turns too quickly and roll over.
Deaths and multimillion dollar lawsuits seem to little to disturb the upward trend in SUV sales. SUVs continue to be extremely popular, accounting for 43 percent of vehicle sales in 2017. Station wagons have become practically extinct, and sales of sedans decline every year, threatening to make them an endangered species.