Diana Kruzman

USA TODAY

The insurance industry's auto safety arm has added three full-size cars to its list of vehicles that have been given the highest rating for crash worthiness, but the Tesla Model S and two others didn't make the cut.

The three receiving the top Top Safety Pick Plus designation from the Insurance Institute for Highway Safety are the Lincoln Continental, the Mercedes-Benz E-Class sedan and the Toyota Avalon. Tesla Model S, Ford Taurus and Chevrolet Impala didn't hit the top mark.

The IIHS is a nonprofit organization funded by auto insurers that crash tests cars, trucks and SUVs to determine crashworthiness.

The Tesla, Impala and Taurus all struggled with the small overlap front test, said David Zuby, a vice president for IIHS, in a statement. The test was introduced in 2012 to test the car’s ability to handle a collision on its front driver-side corner as if it were hitting a telephone pole.

“They need a strong structure so the safety cage, the part in which the driver and the passengers ride, isn’t crushed,” Zuby said.

Tesla stands out in the field because it is the upstart entry into the luxury-car field. It's all electric and has a premium price. CEO Elon Musk has talked frequently about making the car safe.

Zuby said the Tesla Model S didn’t have a strong enough safety belt, and a dummy used to simulate a driver in the small overlap test moved too far forward during the crash, striking its head on the steering wheel. Impala’s structure held up during the test, but the dummy’s head was partially unprotected. And the Taurus, which like the Impala was being tested for small overlap protection for the first time, controlled the dummy’s movement but left its lower left leg exposed to potential injuries.

The Continental, E-Class and Avalon all included appropriate airbag timing and seatbelt tension that helped earn them high safety ratings, Zuby said. The Avalon joins the Kia Cadenza as a Top Safety Pick Plus vehicle in the large cars category, while the E-Class and Continental are now among six vehicles with this designation in the large luxury cars category.

The growing number of vehicles with top safety rankings, Zuby said, gives consumers greater choices when deciding what kind of car they want to buy.

Although the IIHS ranks cars in all size categories, from minicars like the Toyota Yaris to large pickups like the Honda Ridgeline, large cars provide more protection for drivers and passengers. The top safety designation in the large car category, Zuby said, is typically safer than the same rating in the small car category.

“Large cars, by virtue of being large, are safer than smaller ones,” Zuby said.

In 2017, to qualify as a Top Safety Pick Plus, the IIHS says that a car has to pass five safety tests and receive a high rating for front crash prevention. The car also has to have an additional “good” or “acceptable” headlight rating.

The five tests measure how a car responds to small overlap front, moderate overlap front and side crashes, as well as the roof strength and effectiveness of the head restraints.

More cars coverage:Kia tops J.D. Power initial quality survey. See how other cars rank