Two all-electric cars fall short on safety, report finds

The Model S fell short in testing for head restraints and roof strength for the P100D model.

Headlights for the Model S received a poor rating.

During crash testing, the seat belt in the Model S caused the torso of a crash test dummy to move too far forward upon impact, hitting its head against the steering wheel.

"There's no reason the most efficient vehicles can't also be among the safest," said David Zuby, executive vice president and chief research officer for IIHS. "We hope that Tesla and BMW will continue to refine the designs of their electric models to maximize driver protection."

Tesla responded.

"One of the improvements recently introduced in January 2017 specifically addresses the 'acceptable' (or second highest) rating that the Model S achieved in the small overlap frontal crash test, and we expect new tests to yield the highest possible rating ('good' rating) in the crashworthiness category," said Tesla spokeswoman Keely Sulprizio.

Rollover crash testing of the P100D version of the Model S showed a lack of roof strength.

While this car has the same roof as other Model S vehicles, the P100D is heavier, IIHS said.

The BMW i3 missed the mark because of what was found during rear-crash testing for head restraint and seat safety.

The car received an "acceptable" rating in those categories, falling short of a "good" rating.

"We narrowly missed the IIHS rear impact test rating of 'good,' and therefore, the BMW i3 does not achieve a IIHS Top Safety + rating," said spokeswoman Rebecca Kiehne. "However, the BMW i3 with its carbon-fiber structure is designed to meet and exceed global safety standards."

IIHS has plans to test another electric vehicle, the Chevrolet Bolt, once it becomes readily available to the public.