Supersize Electric Cars Are Pushing Road Safety to the Limit
Raul Arbelaez: We’ve been conducting tests on electric vehicles for several years now, but I wanted to be sure that we’re prepared to test something this heavy. So I said, “Can you get me an old junker?” Some older model pickup. Some of the Youtube commenters weren’t too happy that I was calling them junkers. They said, “Hey, I’d fix them up.” But we got them for close to nothing from the junkyard. All I needed to do was hook it up to our propulsion system and figure out if it can get up to our highest crash speed, 40 mph for our frontal crash. My biggest concern was that we wouldn't have enough energy to pull the system. Our system has a series of 16 cylinders that have nitrogen in them, which is compressed to store energy. It typically takes up to four minutes to charge and store that energy. For this test, it approached 10 minutes.
So it worked. And at some point, whether it’s the Hummer or some other EV truck, you’re going to be testing vehicles this heavy. What do you expect from that?
What happened over many years with improvements in powertrain technology is they didn't always go toward making more efficient engines. They went into making more powerful, higher-torque engines that are great for marketing but maybe aren’t the safest thing for people.
With electrification, I hope we can change course. I hope we can say, you know what, we're not going to make this thing 9,500 pounds. We can shave a few thousand pounds off and not get 1,000 horsepower and 300 to 400 miles range and that’s fine. Maybe instead let's focus on infrastructure improvements that make it easier for people to charge more often and get rid of this range anxiety. And can we put in a battery that’s half the mass and save some of those resources and maybe make the vehicle more nimble. But it certainly seems like instead the momentum is in favor of heavier and stiffer cars.
Stiffer too? What does that mean in a crash?
A designer of a heavier vehicle has two choices for managing the extra energy of a crash. The first choice is to make the front-end much longer. There is a little flexibility there, but there are limits. The other option is to increase the stiffness of the front-end. That makes it more dangerous for every other smaller vehicle. You’ll have more people who are vulnerable. All of a sudden that 20 mph crash where the other car was safe isn’t safe anymore.
Just like anything else in safety, there are tradeoffs. You have to design a vehicle in two ways: enough stiffness to handle your own vehicle's mass in a single-vehicle crash, but not so much it’s a battering ram to all other vehicles. Something like a larger pickup has to be stiffer to protect the occupants in the vehicle. But once it hits anything smaller it becomes potentially more dangerous. A lot of the time the path to doing the right thing isn’t obvious.