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Status Report, Vol. 41, No. 10 | December 19, 2006 Subscribe

First crash test results for minicars

For the first time the Institute has tested the smallest vehicles sold in the United States, which gain popularity as fuel prices rise. Now these cars are rated for comparison of occupant protection in front, side, and rear crashes. The Nissan Versa earns good ratings in all three tests. Two other cars earn good ratings in front and side but not rear tests.

Crash test results indicate which vehicles in each weight category afford the best protection in real-world crashes, and this round of tests reveals big differences among the smallest cars. But results of real crashes show that any car that's very small and light isn't the best choice in terms of safety. Driver death rates in minicars are higher than in any other vehicle category. They're more than double the death rates in midsize and large cars.

"People traveling in small, light cars are at a disadvantage, especially when they collide with bigger, heavier vehicles. The laws of physics dictate this," says Institute president Adrian Lund. Death rates in single-vehicle crashes also are higher in smaller vehicles than in bigger ones.

Minicars weigh about 2,500 pounds or less. A typical small car weighs about 300 additional pounds, and midsize cars weigh about 800 pounds more than a minicar. A mid-size SUV weighs 4,000 pounds or more, exceeding the weight of a minicar by at least 60 percent. In every vehicle category (car, SUV, or pickup truck), the risk of crash death is higher in the smaller, lighter models.

"Despite the safety trade-off, more consumers are buying minicars," Lund says. "This is why we tested them. We want consumers to use the ratings to choose the most crashworthy designs among the smallest cars."

Versa is best

Bigger than the other cars the Institute tested this time around, the Nissan Versa is classified a small car, the next size class up from the minis. But this car is marketed to compete with minicars, so the Institute is releasing its ratings along with those of competing models.

The Versa is the only car in this round to earn the highest rating of good in all three tests. In the frontal test, its structure held up well, minimizing intrusion into the space around the driver dummy. Most injury measures were low. In the side test, the standard curtain-style airbags prevented contact between the striking barrier and the heads of the crash test dummies (Nissan is modifying the side airbags in cars built after November 2006 to improve protection in side impacts).

The Institute's side test is especially challenging for small cars because the barrier that strikes the test vehicle represents the front end of a pickup truck or SUV. Side airbags designed for head protection are crucial because the barrier crashes into the side of the car right at the level of the heads of the two dummies that are positioned in the driver seat and in the rear seat behind the driver.

"The Versa is bigger than the other cars we tested, so it has size and weight on its side as well as good test results," Lund says.

The Honda Fit with standard side airbags and the Toyota Yaris equipped with optional side airbags also earn good ratings in front and side tests. However, rear protection isn't rated good. The Yaris is rated marginal for occupant protection in rear impacts, and the Fit's rear rating is poor.

The Institute conducted two frontal tests of the Fit. In the first test the frontal airbag deployed too early, allowing high forces on the driver dummy's head. Honda is modifying the airbags in cars built after November 2006 and says it will recall cars built earlier. In the second test of a Fit with the design change, the frontal airbag deployed properly, and injury measures recorded on the dummy's head were low.


Driver deaths per million registered vehicles by vehicle weight, 2000-04 models during 2001-05

graph

Rates are adjusted for some differences in driver age and sex within and between vehicle types. Remaining differences plus driver demographics may account for some of the death rate differences.

Minicars aren't the best choices in terms of safety because small, light vehicles afford less protection than ones that are larger and heavier. There's less structure to absorb crash energy, so deaths and injuries are more likely to occur in both single- and multiple-vehicle crashes.

Bigger generally is safer

This doesn't mean the very heaviest vehicles are the only safe choices because those weighing more than about 4,500 pounds afford only small injury risk reductions. Meanwhile they increase the injury risks for people in the other vehicles with which they collide, especially when the other vehicle is a small, light minicar.

While the risk of death generally is higher in minicars than in bigger vehicles, size and weight don't tell the whole story. Some minicar models are safer than others because some have more crashworthy designs. The Institute's ratings highlight these differences.


Side tests trip up four cars

The Hyundai Accent, Scion xB, and the Toyota Yaris without its optional side airbags earn poor ratings in the side test. The Chevrolet Aveo is marginal. The Accent and Aveo didn't perform well even though they have standard side airbags. The Aveo's front seat-mounted side airbags did a good job of protecting the driver dummy's head, but this car's structural performance was marginal. Intrusion into the occupant compartment led to high forces on the driver dummy's pelvis. There's no side airbag protection for rear-seat passengers, and the barrier struck the dummy's head.

The Accent's structural performance in the side test also was marginal. Curtain-style airbags in front and rear seats provided good head protection, but measures recorded elsewhere on the driver dummy indicate a motorist in a similar real-world crash would sustain internal organ injuries, broken ribs, and a fractured pelvis.

Overall the Accent is the lowest-rated car in this group. The rank order takes into account all three ratings (front, side, and rear).

Another poor performer in the side test is the Scion xB. Side airbags aren't available, and the xB's side structure didn't do a good job of resisting intrusion during the impact. The barrier intruded into the car and struck the driver dummy's head. Measures indicate the likelihood of brain injuries, serious neck injuries, and a fractured pelvis in a real-world crash of similar severity.

"The Scion's poor side rating and marginal rating in the rear test are especially disappointing because this car is marketed to young drivers, who have the highest crash rates and thus the greatest need for crashworthy vehicles," Lund says. "Toyota says it will replace the current xB design later in the 2007 model year, and hopefully the new version will be a better performer."

People often choose to buy very light cars for fuel economy but "you don't have to buy the smallest, lightest car to get one that's easy on fuel consumption," Lund points out. "Models including the Honda Civic, not even the hybrid version, and Toyota Corolla are bigger than the minicars we tested and weigh more, so we would expect better occupant protection in serious crashes. At the same time, these and other small car models get nearly as good fuel economy as minicars."

Rear protection isn't keeping pace

Cars have been earning good ratings in frontal crash tests for several years, and now improvements in side crash protection are accelerating. But the seat/head restraints in many cars still don't provide adequate protection for most people in rear-end crashes. This is the case among the cars the Institute recently tested. Every model except the Versa, classified a small car, earns a low rating of marginal or poor.

"When a vehicle's seat/head restraint design isn't good, people are more likely to suffer neck injuries in rear impacts," Lund points out. This is the most common crash type in commuter traffic. More than 2 million insurance claims are filed for whiplash each year, costing more than $8 billion. About 1 in 10 of these injuries results in long-term pain and/or disability.

To reduce this burden, seats and head restraints have to work in concert to support people's necks and heads, accelerating them along with the torso as the vehicle is driven forward. The head restraint has to be tall enough and close enough to the back of the head to catch it early in a crash, and the seat has to have some "give" to help keep the head and torso moving together (see Status Report special issue: protection against neck injury in rear crashes, Nov. 20, 2004).

"The seat/head restraint combinations in every car we tested this time around except the Versa wouldn't provide adequate protection against whiplash," Lund says.

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