The Tesla 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. The ratings for the Model S apply to 2016 and 2017 cars built after October 2016. Tesla says it made a production change on Jan. 23 to address the head-contact problem, and IIHS will test the updated vehicle for small overlap protection as soon as it can be delivered.