The National Highway Traffic Safety Administration has awarded the Tesla Model S a 5-star safety rating -- not just overall, but in every subcategory without exception, Tesla Motors announced.

Approximately 1 percent of all cars tested by the federal government achieve 5 stars across the board. NHTSA does not publish a star rating above 5, but safety levels better than 5 stars are captured in the overall Vehicle Safety Score (VSS) provided to manufacturers. The Model S drew a new combined record of 5.4 stars, Tesla said. Of all vehicles tested, including every major make and model approved for sale in the United States, the Model S set a new record for the lowest likelihood of injury to occupants.

Though the Model S is a sedan, it also exceeded the safety score of all SUVs and minivans. This score takes into account the probability of injury from front, side, rear and rollover accidents.

In the front, the Model S has the advantage of not having a large gasoline engine block, thus creating a much longer crumple zone to absorb a high-speed impact, the automaker pointed out. This is fundamentally a force-over-distance problem – the longer the crumple zone, the more time there is to slow down occupants at g loads that do not cause injuries. Just like jumping into a pool of water from a tall height, it is better to have the pool be deep and not contain rocks. The Model S motor is only about a foot in diameter and is mounted close to the rear axle, and the front section that would normally contain a gasoline engine is used for a second trunk.

For the side pole intrusion test, considered one of the most difficult to pass, the Model S was the only car in the "good" category among the other top 1 percent of vehicles tested. The Model S preserved 63.5% of driver residual space. Tesla said it achieved this outcome by nesting multiple deep aluminum extrusions in the side rail of the car that absorb the impact energy and transfer load to the rest of the vehicle. This causes the pole to be either sheared off or to stop the car before the pole hits an occupant. 

The rear crash testing was particularly important, given the optional third-row children's seat. For this, the Tesla factory installs a double bumper if the third-row seat is ordered. This was needed to protect against a highway speed impact in the rear with no permanently disabling injury to the third-row occupants. The third row is already the safest location in the car for frontal or side injuries.

The Model S was also superior in rollover risk tests. During testing at an independent facility, the Model S refused to turn over via the normal methods and special means were needed to cause the car to roll. That’s because the battery pack is mounted below the floor pan, providing a very low center of gravity.

During validation of Model S roof crush protection at an independent commercial facility, the testing machine failed at just above 4 g's. While the exact number is uncertain because the Model S broke the testing machine, this means that at least four additional fully loaded Model S vehicles could be placed on top of an owner's car without the roof caving in. This is achieved primarily through a center (B) pillar reinforcement attached via aerospace-grade bolts, Tesla said.