All-electric Model S sedan receives 5-star safety rating
All-electric Model S sedan receives 5-star safety ratingTesla Model S sedan is setting the bar, not just for electric vehicles, but for the entire automotive industry.
In November of last year, the car was named Automobile Magazine's 'Automobile of the Year,' besting any other vehicle produced in 2012--electric or otherwise. Motor Trend Magazine agreed, bestowing their coveted 'Car of the Year' award on the Model S.
And it wasn't just automotive enthusiast publications singing the car's praises. In May, Consumer Reports called the Model S the best car it had ever tested. "Let me repeat that," said Consumer Reports director of automotive testing Jake Fisher, "not just the best electric car, but the best car." They awarded the Model S a 99 out of 100 rating, tied for the highest Consumer Reports score ever conferred on an automobile.
Building on this trend, Tesla has just announced that the Model S has achieved the best vehicle safety score of any vehicle ever tested by the National Highway Traffic Safety Administration.
"Independent testing by the [NHTSA] has awarded the Tesla Model S a 5-star safety rating, not just overall, but in every subcategory without exception," Tesla said in a release. "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."
Tesla says that, while the NHTSA does not publish scores above 5 stars, it does provide an overall vehicle safety score, or VSS, to manufacturers. The Model S scored off the charts, with a VSS of 5.4, exceeding the combined safety score of any car, SUV or minivan ever tested.
Tesla credits its large front crumple zone--where you would typically find the engine on a gas car--for being able to better absorb the impact of the NHTSA's frontal crash test.
In the side pole intrusion test, Tesla outdid the competition by a wide margin. "Compared to the Volvo S60, which is also 5-star rated in all categories, the Model S preserved 63.5 percent of driver residual space vs. 7.8 percent for the Volvo," said the automaker. Tesla attributes its success in this test to "multiple deep aluminum extrusions in the side rail of the car that absorb the impact energy," an approach that the automaker says was used on the Apollo Lunar Lander.
To round out the battery of tests (no pun intended), Tesla points to a robust double bumper protecting the car's rear and heavy batteries keeping the car stable during rollover testing. "The Model S refused to turn over via the normal methods and special means were needed to induce the car to roll," according to the automaker.
In preparing the Model S for production, Tesla says they commissioned a series of internal tests to validate the vehicle's safety. During a "roof crush protection" test, the automaker claims that the Model S actually broke the testing machine, after withstanding over 4 G's of pressure.
UPDATE: ABC News is reporting that the National Highway Traffic Safety Administration (NHTSA) is "pushing back on Tesla Motors' claim that its Model S car had a crash test rating greater than five stars." This is in reference to a statement made on the the NHTSA website that says, "NHTSA does not rate vehicles beyond 5 stars and does not rank or order vehicles within the star rating categories." The agency's communication usage guidelines further state, "NHTSA strongly discourages the use of potentially misleading words such as 'perfect,' 'safest,' 'flawless' or 'best in class' to describe the star rating received by the vehicle."
None of the discouraged phrases are explicitly mentioned in Tesla's press release and, as we originally reported, Tesla notes that the NHTSA does not publish scores above 5 stars.
We reached out to Tesla for further clarification. The automaker says it stands by its press release, and provided the following reasoning for their claimed 5.4 combined vehicle safety score:
NHTSA defined 5 stars as 10 percent or less risk of injury for frontal crash, 5 percent or less chance for injury for side impact, and 10 percent or less risk for rollover. For our safety tests, we assume that means that 6 stars is 0 percent risk of injury. Both probability (P) and Relative Risk Score (RRS) go into the star ratings.
While Tesla's claimed 5.4 combined vehicle safety score may not have the blessing of the NHTSA, all parties can agree that the electric Model S sedan has received a 5-star safety rating across the board.
SETS NEW NHTSA VEHICLE SAFETY SCORE RECORD
MONDAY, AUGUST 19, 2013
Palo Alto, CA - Independent testing by the National Highway Traffic Safety Administration (NHTSA) has awarded the Tesla Model S a 5-star safety rating, not just overall, but in every subcategory without exception. Approximately one percent of all cars tested by the federal government achieve 5 stars across the board. NHTSA does not publish a star rating above 5, however safety levels better than 5 stars are captured in the overall Vehicle Safety Score (VSS) provided to manufacturers, where the Model S achieved a new combined record of 5.4 stars.
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. While 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.
The Model S has the advantage in the front of not having a large gasoline engine block, thus creating a much longer crumple zone to absorb a high speed impact. 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 one percent of vehicles tested. Compared to the Volvo S60, which is also 5-star rated in all categories, the Model S preserved 63.5 percent of driver residual space vs. 7.8 percent for the Volvo. Tesla achieved this outcome by nesting multiple deep aluminum extrusions in the side rail of the car that absorb the impact energy (a similar approach was used by the Apollo Lunar Lander) 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, Tesla factory installs a double bumper if the third row seat is ordered. This was needed in order 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 substantially better in rollover risk, with the other top vehicles being approximately 50 percent worse. During testing at an independent facility, the Model S refused to turn over via the normal methods and special means were needed to induce the car to roll. The reason for such a good outcome is that the battery pack is mounted below the floor pan, providing a very low center of gravity, which simultaneously ensures exceptional handling and safety.
Of note, 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 due to Model S breaking the testing machine, what this means is 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.
The above results do not tell the full story. It is possible to game the regulatory testing score to some degree by strengthening a car at the exact locations used by the regulatory testing machines. After verifying through internal testing that the Model S would achieve a NHTSA 5-star rating, Tesla then analyzed the Model S to determine the weakest points in the car and retested at those locations until the car achieved 5 stars no matter how the test equipment was configured.
The Model S lithium-ion battery did not catch fire at any time before, during or after the NHTSA testing. It is worth mentioning that no production Tesla lithium-ion battery has ever caught fire in the Model S or Roadster, despite several high speed impacts. While this is statistically unlikely to remain the case long term, Tesla is unaware of any Model S or Roadster occupant fatalities in any car ever.
The graphic below shows the statistical Relative Risk Score (RSS) of Model S compared with all other vehicles tested against the exceptionally difficult NHTSA 2011 standards. In 2011, the standards were revised upward to make it more difficult to achieve a high safety rating.