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Is Tesla S the safest car ever?

Company claims safety rating beyond that endorsed by U.S. government agency

Published: August 26, 2013, 8:15 PM

Tesla Model S - Front

Tesla founder, Elon Musk is well known for pushing the limits, as his visionary achievements with PayPal, Space-X and Tesla itself attest.

But sometimes that trait can lead to pushing the limits of credibility, as was the case with a recent press release from Tesla, touting the crash performance of the Tesla Model S.

It wasn't that the car performed poorly. Quite the contrary. It achieved five-star ratings in each of the crash-test modes prescribed by the U.S.National Highway Traffic Safety Administration (NHTSA), as well as five stars overall – the highest ratings possible.

It's an impressive result. But not impressive enough for Tesla, apparently.

While it's not the only car to have achieved an overall five-star rating, the company announced that it was the best safety rating of any car ever tested, then went a step further.

While acknowledging that NHTSA does not publish a star rating above 5, Tesla said safety levels better than 5 stars are captured in the overall Vehicle Safety Score (VSS) provided to manufacturers. And it interpreted those results as "a new combined record of 5.4 stars" for the Model S.

NHTSA quickly responded with what could be considered a slap on the wrist for Tesla, by posting the following notice on its website:

"NHTSA does not rate vehicles beyond 5 stars and does not rank or order vehicles within the star rating categories. In addition, the agency has guidelines in place for manufacturers and advertising agencies to follow to ensure that accurate and consistent information is conveyed to the public."

Those guidelines "strongly discourage" the use of superlatives such as "safest" or "best in class."

NHTSA's reprimand notwithstanding, the Tesla S did pass the government-mandated crash tests by significant margins.

In the frontal crash test, its good performance was attributed to the lack of a rigid gasoline engine up front, thus enabling a long crumple zone to help absorb a high speed impact. (The Model S's electric motor is mounted in the rear.)

For the side pole intrusion test, considered one of the most difficult to pass, the Model S was the only car in the "good" category among the other top one-percent of vehicles tested. Compared to the Volvo S60, which also achieved 5-star ratings in all categories, the Model S was said to preserved 63.5% of the driver's residual space, compared to 7.8% for the Volvo.

For protection in a rear-end crash Tesla installs a double bumper if a third row seat is ordered.

The Model S particularly excelled in terms of rollover risk, because of the low centre-of-gravity (CG) resulting from mounting of the cars batteries (its greatest concentration of mass) below the floor pan.

In terms of roof crush protection, the Model S sustained the equivalent of more than four similar vehicles stacked on top without the roof caving in.

It is important to note that the NHTSA star rating system is based on performance in the crash and safety tests mandated by the U.S. and Canadian governments. The are different from tests and ratings established by the U.S.-based Insurance Institute for Highway Safety (IIHS).

IIHS test results, which are frequently cited in vehicle advertising, tend to be more severe than the mandated government tests.

It should also be noted that both sets of ratings are based on occupant protection in the event of a crash and do not consider the effects of crash-avoidance technologies.