Two all-electric vehicles fall short of meeting the Institute's awards criteria, but consumers who want to minimize gas consumption while also prioritizing safety can choose from two plug-in hybrids that earn the 2017 TOP SAFETY PICK+ award.
The two recently evaluated 2017 all-electric models are the Tesla Model S and the BMW i3. The plug-in hybrid models are the Chevrolet Volt, whose award was announced in December, and the Toyota Prius Prime.
"There's no reason the most efficient vehicles can't also be among the safest," says David Zuby, IIHS executive vice president and chief research officer. "We hope Tesla and BMW will continue to refine the designs of their electric models to maximize driver protection and, especially in the case of Tesla, improve their headlights."
To qualify for TOP SAFETY PICK, a vehicle must earn good ratings in all five crashworthiness evaluations — small overlap front, moderate overlap front, side, roof strength and head restraints — and have an available front crash prevention system that earns an advanced or superior rating. The "plus" is awarded to vehicles that meet all those criteria and also come with good or acceptable headlights (see "In the best light: 2017 TOP SAFETY PICK+ winners meet new headlight criteria," Dec. 8, 2016).
The Model S, a large luxury sedan, earns good ratings in all IIHS crashworthiness evaluations except the challenging small overlap front crash test, in which it earns an acceptable rating. Despite lengthening the side curtain airbags to improve small overlap protection in the Model S, Tesla ran into problems in the test when the safety belt allowed the dummy's torso to move too far forward. That allowed the dummy's head to hit the steering wheel hard through the airbag. Measurements from the dummy indicated that injuries to the head, along with the lower right leg, would be possible in a real-world crash of the same severity.
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. Since the kinetic energy involved in a front crash depends on the speed and weight of the vehicle, the Tesla's acceptable rating is based on a more severe crash than the good ratings of the lighter cars.
One version of the Model S, the P100D, also falls short on roof strength, which is important for protecting people in a rollover crash. The rating is based on a strength-to-weight ratio. The P100D has the same roof structure as other Model S versions but is heavier, due to a larger battery, so it earns an acceptable rating.
The current version of the Model S hasn't yet been rated for front crash prevention. While automatic braking equipment comes standard, Tesla hasn't yet activated the software for all vehicles.
The 2017 Model S isn't available with anything other than poor-rated headlights. Tesla says it is working with its supplier to improve the headlights, and IIHS will evaluate the new ones when they are available.
The i3, a small car, fails to reach the winner's circle because it rates only acceptable in the head restraint and seat evaluation, which measures a vehicle's ability to protect against neck injuries in a rear crash. While such injuries are rarely fatal, they are the most common type of crash injury and can cause debilitating pain.
The i3's only available headlight system earns an acceptable rating.
"BMW clearly thought a lot about safety when designing the i3," Zuby says. "It's a shame that it missed the mark on head restraints, which is something most of today's vehicles get right. Among small cars, the i3 is the only 2017 model that doesn't earn a good rating."
The 2017 Volt can be optionally equipped with either an advanced- or superior-rated front crash prevention system. It earns a good rating for headlights when equipped with optional high-beam assist, which automatically switches between high beams and low beams based on the presence of other vehicles. Without high-beam assist, the Volt's headlights are acceptable.
The Prius Prime is the plug-in version of the Prius hybrid, also a TOP SAFETY PICK+ winner. Its standard front crash prevention system earns a superior rating, and its only available headlights earn an acceptable rating.
While the Volt and the Prius Prime can both run on gas, the Volt has an edge in electric-only driving. It can travel 53 miles in electric-only mode, while the Prius Prime can go 25 miles without using gas, according to EPA estimates. When it hasn't been plugged in, the Prius Prime gets 54 miles per gallon, while the Volt gets 42 mpg.
IIHS plans to test another green car, the all-electric Chevrolet Bolt, once it becomes widely available later this year.