For a vehicle to qualify for the Top Safety Pick award, IIHS said it must earn "good" ratings in all five crashworthiness tests - small overlap front, moderated overlap front, side, roof strength, and head restraints and seats - and come with a front crash prevention system that earns an advanced or superior rating.
The IIHS also raised concerns about the possibility of lower leg injuries during the same test. Tesla confirmed that it had fixed the problem, and wrote in an email that it would be beefing up its crash safety even further with an "automatic emergency breaking" feature, which will be rolled out as an over-the-air software update "in the coming weeks".
Although the i3, the Volt and the Prius all did better in the small overlap evaluation than the Model S, the results can't be compared because the Model S is larger than the others. They excelled in front, side and roof crash protection and safety of their head restraints. Tesla says it is working with its supplier to improve the headlights, and IIHS will evaluate the new ones when they are available.
The Model S also would not have qualified for the award since IIHS has not rated it for front crash prevention. If a vehicle meets the requirements and passes the assessments, it can earn the "Plus" moniker if its headlights are found to be good or acceptable, as explained in a video below. Achieving a "good" rating in all five would enable the vehicle to be designated as an IIHS top safety pick.
The BMW i3 fell short in the head restraint test, which measures how well the auto protects an occupant's head in a rear crash. In the other four tests conducted, the vehicle managed to get a "good" rating.
According to IIHS, the tests were on Tesla cars built after October 2016. Secondly, the roof of the Model S P100D that was tested wasn't strong enough to ensure safety in a rollover, due to the car's weight.
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National environmental groups joined the fray soon after, bringing the issue to global attention. But a local tribe opposed to the pipeline vowed to continue to fight the project in court.
Most recently the 2017 BMW 2 Series Coupe was awarded a "Top Safety Pick" in the 2017 IIHS TSP/TSP+ in early December 2016.
Conversely, the Volt can go longer in electric-only mode at 53 miles while the Prius tops out at 25 miles.
According to the new test ratings that were released by IIHS after the test of vehicle crash test, it was found that Tesla's electric auto was not able to score the highest ratings.
The IIHS says it plans to test the Chevrolet Bolt EV electric vehicle soon.
Tesla says it made a change to its production line on January 23 that modified its seat belt position to address the head-contact problem, and will deliver a new vehicle for IIHS for small overlap crash testing.