In August, Tesla Motors announced that its Model S electric vehicle had received the highest safety rating in the United States, achieving "a new combined record of 5.4 stars" based on crash test data. There's only one problem with that: the US National Highway Transportation Safety Adminstration, which conducts those tests, doesn't give ratings over five stars — period. So today, the NHTSA is attempting to set the record straight, revising its advertising guidelines to forbid automakers from stating that a car received a higher score.

The new advertising guidelines actually don't explicitly mention Tesla, and they're really not solely targeted at the electric automaker at all. They also state that vehicle manufacturers shouldn't advertise cars with phrases like "double 5-star rating" — as some have when a car merely recieves five stars for both the driver and passenger safety — or implying that an entire vehicle received a five-star rating when, say, it only recieved five stars for front impact collisions.

Could a 6-star rating make sense?

That said, Tesla has an interesting case. While there may not be such a thing as a 5.4-star rating right now, the actual safety scores Tesla received might put the Model S in the vicinity of 5.4 stars if such a rating existed. A Tesla spokesperson explained to The Verge that while the NHTSA presently defines five stars as a 10 percent or less risk of injury from combined and weighted crash scores, the Tesla Model S has a roughly 7 percent risk of injury using those same calculations. If you assume that a hypothetical 6-star rating would be given to vehicles with 0 percent risk of injury in a crash — as Tesla did — a 5.4-star rating might be apt. That assumes, of course, that it makes sense to count down to zero percent risk in such a fashion.