Tesla Motors' recent five-star sweep in the National Highway Traffic Safety Administration (NHTSA) safety ratings shed light on an important aspect of electric cars: They’re inherently safer than vehicles powered by internal combustion engines.
Tesla’s Model S served as a prime example of those safety advantages, recording the highest (five-star) ratings in frontal, side, rollover, and overall crash categories. The Model S joined the 2013 and 2014 models of the Ford Focus EV, which also captured five-star NHTSA safety ratings across the board.
Experts said that the performance by both vehicles was not surprising. “There are some very inherent safety dimensions to the design of an electric vehicle,” David Cole, chairman emeritus of The Center for Automotive Research, told Design News. “The design may have had more to do with energy storage and powertrain issues, but the safety advantage is a gift that comes along with it, and it’s very real.”
Tesla Model S’s lithium-ion batteries are placed low in the vehicle, dropping its center of gravity. (Source: Design News)
Cole noted that electric cars have three primary safety advantages over their gasoline-powered counterparts. The first is that the batteries are located low in the vehicle, dropping the center of gravity and reducing the possibility of rollover. The second is the elimination of the internal combustion engine, which typically transmits crash energy rearward.
”An engine block is just too rigid,” Cole told us. “So the shock wave is pretty much transferred to the area directly behind the engine, with minimal energy absorption.” In contrast, he said, electric car batteries deform and absorb energy during a crash.
The EV’s other key safety advantage is the elimination of gasoline, Cole said. “You don’t have a highly volatile liquid onboard, which can quickly get away from you during a crash and become a real problem."
In a press release, Tesla claimed that its Model S was approximately 50 percent better than other top vehicles in rollover tests. “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 release said.
A separate claim by Tesla that “the Model S achieved a new combined record score of 5.4 stars” has since been refuted by NHTSA. A statement on the government agency’s website said “NHTSA does not rate vehicles beyond five stars and does not rank or order vehicles within the star rating categories.”
Tesla’s high-profile effort to publish its safety news may serve as an important step for the electric car market, however. Companies that build gasoline-burning cars have been less inclined to publish such news, Cole said. “With the exception of Tesla, manufacturers are not going to talk about this,” he explained. “Most EV makers sell a lot more internal combustion engine cars than electric cars, so it’s not something they want to publicize.”
To date, electric cars have done well in NHTSA ratings, although several have yet to be rated. The Nissan Leaf and Mitsubishi iMiEV have received mostly four-star ratings, while the Fit EV, Spark EV, Fiat 500e EV, and RAV4 EV are awaiting evaluation. Chevy’s Volt, which incorporates a 16-kWh lithium-ion battery along with an internal combustion engine, received mostly fives in its NHTSA evaluation. Thus far, Tesla and Ford are the only automakers to receive across-the-board five-star ratings on their EVs.
“They’ve definitely done a good job with the design of those cars,” Cole said. “There’s no question about that.”
I too would like to know if the battery packs are damaged and leaking is it an environmental hazard? Certainly not all electrolytes are created equal and some of them must be toxic. It would be interesting to know how first-responders or clean-up crews deal with it.
Telsa's publishing of safety news certainly leaves other companies with fewer choices. If they counter Telsa by publishing such news, they will be advertising against their gasoline powered vehicles. On the other hand, if they don't publish, they will be compromising their EVs. I believe, however, that it will not hurt them as much as it seems apparently. Because what they might lose in gasoline powered vehicles they will gain in EVs.
@ Rob Spiegel, it is clearly stated in the article that EVs have at least three inherent safety advantages over their gasoline powered counterparts. But I think it is more about Telsa than EVs because some other EVs by other companies got four stars. There must be something more than these three inherent advantages in Telsa's Model S that got it five stars.
I don't know the definitive answer to your question, bobjengr, but I'm not familiar with any NHTSA standards that target only EVs, ICEs, or hybrids. Is there a reader out there who can enlighten us on this?
Well, I think - based on some very vague observations, the ICE can be very reliable and about as safe as any other rapidly moving vehicle with slow witted humans in control. Minor design and manufacturing errors can make it unsafe at any speed. Similarly the battery car can be extreemly safe. And while it may do a thermite thing, it is not as likely to spray you with burning fuel when ruptured. Unfortunatly the failure mechanisms are less familiar to both the typical user, the maintenance personel, and the designers.
Of the two - however - only one gets you to work when solar/wind/nuclear are the only inexpensive energy sources and gasoline tops $4 a gallon. And a bit odd at that. I thought coal-oil (nuclear assisted or not) was around $2/gal which should mean our very cost conscious market should now be producing coal oil for our cars, not gasoline??? Is there a problem here way way beyond just the obvious one with a (relativly) new battery technology, and it's annoying limitations???
"Gasoline is poisonous, forms explosive mixtures with air, and is quite flamable. Batteries - because they carry both fuel and oxidizer - can burn without air. The better the battery the hotter it burns. The Li Ions are pretty good at doing the thermite thing. Overall, I do not feel either one is particularly "safe", just different risks."
Fred, you are right; risks are associated with all source of energy. The only question is which is minimal and economical
NHTSA mandates three major types of crash testing:
1. Frontal impact. There are several subcatagories based on overlap between vehicles (100% overlap, 50% overlap and 25% overlap). Some impacts are with a massive concrete barrier. Others are into softer "deformable" barriers.
2. Side Impact. A test sled is driven into the target vehicle at a specified speed and mass.
3. Rollover. The test vehicle is driven or pulled onto a helical ramp which then triggers the rollover.
There is also some rear impact testing, mainly to verify head restraint performance, seat attachment robustness, and fuel leakage.
IIHS (Insurance Institute for Highway Safety) often performs additional testing or testis to more severe conditions than mandated by NHTSA regulations.
The auto industry has learned a lot about how to improve the crashworthiness of vehicles over the past 30 years. However, Tesla has a definite advantage because they began with a clean sheet design. They could then address all the crashworthyness regulations from the beginning, making design decisions that could optimize crush zone characteristics which reduced occupant injuries.
Disclosure: I spent a majority of my career designing electronics to mitigate occupant injuries in crashes.
I haven't had a chance to read all the comments here, but I've looked at a few and some are making the case that lithium-ion chemistries aren't safe. And, yes, it's true that lithium-ion (particularly cobalt oxide chemistries) are more energetic than other battery chemistries. But bear in mind that gasoline has a much, much higher energy density than any battery...yet engineers have been able to make gasoline-burning vehicles very safe.
Leto, you are probably correct, but I was thinking that if I were driving a car that expensive I would be very careful indeed. Even with my present car I have avoided being hit by taking the initiative and getting out of the way of some people. So it is possible for some of us to pay enough attention to avoid the errors of others. At least sometimes. But there are a lot of other folks who would never consider getting out of the way of a car sliding towards them, because the have a right to be where they were. I consider that to be quite dumb.
For industrial control applications, or even a simple assembly line, that machine can go almost 24/7 without a break. But what happens when the task is a little more complex? That’s where the “smart” machine would come in. The smart machine is one that has some simple (or complex in some cases) processing capability to be able to adapt to changing conditions. Such machines are suited for a host of applications, including automotive, aerospace, defense, medical, computers and electronics, telecommunications, consumer goods, and so on. This discussion will examine what’s possible with smart machines, and what tradeoffs need to be made to implement such a solution.