The New York Times Blogs (Wheels)
August 23, 2013
The Tesla Model S just received the government’s highest safety rating. What are the implications for electric vehicles (EV) in general?
Are electric cars not simply cleaner, but safer as well? The high federal safety rating given to the Tesla Model S this week suggests that key elements of the electric sedan’s design may have positive implications for passenger safety.
But the money spent on engineering and building the luxury car is also a factor, and that may be harder to replicate in EV's aimed at the mass market.
The 2013 Model S got an overall combined score, called the overall Vehicle Safety Score, of 0.42. This is the lowest score - and in this case lower is better - of any vehicle that NHTSA has tested under a new rating system it began applying to 2011 models. However, the 2012 Chevrolet Camaro came close with a score of 0.47, and it isn't electric. The score of the 2013 Nissan Leaf, which is an electric car, was 0.77. The Model S has not yet been evaluated in crash tests performed by the Insurance Institute for Highway Safety. Since the institute's tests are different from NHTSA's, and some are more demanding, there is no way to know what the results will be until the institute, which is financed by the insurance industry, actually smashes a few Tesla EV's. Tesla put in a request to undergo the institute's testing regimen, but no tests are currently planned, said Joe Nolan, the vice president for vehicle research at the institute.
The design of current EV's can provide some safety advantages, Nolan said. By not having a big engine under the hood, there is more room to absorb the energy of a front crash before it reaches the passenger compartment.
"With these new drivetrain variants—electric, hydrogen—the vehicle package can be different than we are all accustomed to," Nolan said. "And if you can have more efficient energy absorption in the front, that means you can deal with frontal crashes better; and that seems to be borne out in the NHTSA testing of the Tesla."
In addition, Nolan said, heavier vehicles fare better in crashes than light ones no matter how they are propelled.
"The fact that this particular design needs fairly heavy batteries helps it," he said. "And it really helps that those batteries are low on the vehicle, so you get a rollover benefit as well."
Still, if an EV were designed differently, it might not have the same safety benefits, he said.
Tesla's results could also could have something to do with the car's significant price tag, said Clarence M. Ditlow, executive director of the Center for Auto Safety. With a starting price of $69,900, before a federal tax credit of $7,500, Tesla Motors can afford to spend more on engineering than automakers selling electric cars of the $40,000 variety.
"It is clear they are paying attention to engineering," Ditlow said. "When you make a luxury car, the buyers expect you to build safety in. They are doing what they should be doing."
In its news release about the safety rating, Tesla Motors noted that the testing machine at an independent facility "failed at just above 4Gs" during a roof crush validation test for the Model S. Tesla claimed that the test result meant that "at least four additional fully loaded Model S vehicles could be placed on top of an owner's car without the roof caving in." The company attributed the results to a B-pillar reinforcement attached with aerospace-grade fasteners.
Nolan of the insurance institute said he did not think the roof-crush test results had anything to do with EV design or mass. His institute also conducts roof crush tests; to get the top rating of "Good," a vehicle must be able to withstand a force equal to four times its weight before reaching five inches of crush.
"There are lots of vehicles that earn 'Good' ratings in the roof crush test and that can either hold up four times their weight or more," Nolan said. "It's a good thing, but it's not that unique."
NHTSA's New Car Assessment Program rates vehicles on a scale from 1 (the lowest) to 5 (the highest) stars. So Tesla's claim in a news release that the Model S received a 5.4-star rating seems strange. In response to a request for comment, the agency said in a statement that "NHTSA does not rate vehicles beyond five stars and does not rank or order vehicles within the starred categories."
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