from Hacker News

Electric vehicle safety via crash test

by Gabriel54 on 10/10/24, 2:32 AM with 52 comments

  • by Animats on 10/10/24, 5:27 AM

    Overview of guardrails - reasonably good video. [1]

    Motor Trend: "America's vehicles are fat, and its guardrails suck."[2] Motor Trend is critical of the U.Texas tests, because they didn't test larger gas-powered trucks. The current guardrail test weight for pickup trucks is 5000 pounds. That was increased from 4500 pounds in 2019. Current Ford F-150 trucks can be over 7,000 pounds, empty. The Rivian EV pickup is listed as 7,148 lbs. The Hummer EV is over 9000 lbs.

    Guardrails have ratings - TL1 through TL6. TL3 is most common. That's the 5000 pound pickup truck level. The standard test is not straight-on; it's 45 degrees. After all, these things are alongside roads, and are rarely hit straight on at high speed.

    The last big problem with guardrails was collisions with guardrail ends, especially at freeway offramps. There are good solutions for that in place now. Take a good look at the high-traffic Interstate offramp you see. There are various different crushable systems used, and they work reasonably well. The main problem is replacing them after use. They're a consumable.

    Low center of gravity is a big problem. Guardrail heights have been increased over the last few decades as cars got bigger. Low-CG electrics push their way under. Notice, though, that the Tesla test resulted in the vehicle traveling parallel to the guardrail after the vehicle went under it. Enough energy was absorbed to redirect the vehicle. The Rivian went clear through.

    Maybe for pickups above some weight drivers should have to have a commercial driver's license, the one you need to drive a real truck.

    [1] https://www.youtube.com/watch?v=w6CKltZfToY

    [2] https://www.motortrend.com/news/guardrail-safety-study-evs-p...

  • by bryanlarsen on 10/10/24, 4:16 AM

    Poorly designed EV's without a bespoke chassis are 20-30% heavier than gasoline cars. But better designed ones are much closer in weight, and those are the cars that sell well.

    For example, a Tesla 3 is within 5% of the weight of a BMW 3.

  • by wenc on 10/10/24, 3:00 AM

    Just curious, is this an EV thing or just a high weight and low center of gravity thing? Because a number of gas cars also fall into the latter category.

  • by esjeon on 10/10/24, 3:11 AM

    Upgrading all guardrails isn’t terribly difficult - it just takes long. Guardrails usually last 20-30 years, and governments will not replace them until they fail.

    Also, this experiment also means that BEVs can inflict bigger damages to other hard objects (e.g. buildings), and drivers would get injured more seriously during collision. So I think we should get a safer design that kills the kinetic energy on collision.

  • by breakyerself on 10/10/24, 3:06 AM

    It showed a Tesla crashing at a high rate of speed and steep angle. Didn't show a comparable ice car. I am distracted by the TV. Did I miss it?

  • by kmoser on 10/10/24, 3:11 AM

    I'm surprised it took this long to figure it out. I would have thought every new model of car would be subjected to guardrail crash tests, starting with the earliest EVs and hybrids from several decades ago (Prius in late 1990s, Tesla in mid-2000s). Or maybe the media is just slow on the uptake?

  • by MBCook on 10/10/24, 3:29 AM

    Maybe we should just have reasonable weight and size limits?

  • by helsinkiandrew on 10/10/24, 4:12 AM

  • by jader201 on 10/10/24, 3:06 AM

    The test seems to be sending the EV into the guardrail at a 45 degree angle, moving straight ahead. Is this common for guardrail collisions?

    Granted, it’s ideal if they can withstand that angle of impact, but I’m trying to understand the real world impact to safety this has.

  • by diebeforei485 on 10/10/24, 6:39 PM

    What they don't say is: (1) Vehicles are heavier now, not just EV's. (2) Regardless of the barriers you are safer in an EV because EV's don't rollover.

  • by yieldcrv on 10/10/24, 2:56 AM

    Skip to 1:05 if you value your time to see the first video examples

  • by ekianjo on 10/10/24, 3:12 AM

    Makes no sense. pick up trucks in the US are way larger and heavier than regular EVs and they don't seem to raise an alert on that.

  • by userbinator on 10/10/24, 3:06 AM

    one piece of this was noticing EVs weigh 20 to 30% more than their gas-powered counterparts.

    ...which isn't much on the absolute scale; the difference in weight between a small sedan and a larger one, or an SUV or truck. If EVs weren't being stopped by guardrails, neither were the latter.

  • by erikaww on 10/10/24, 3:02 AM

    Couldn’t this be engineered away? Put half the battery on top and another on the bottom

  • by 01HNNWZ0MV43FF on 10/10/24, 3:00 AM

    Another reason to buy a Prius

    > It’s not only the weight of the vehicle, TTI said. The battery used to power EVs creates a lower center of gravity and the front is a storage space instead of an engine compartment.

  • by wg0 on 10/10/24, 3:16 AM

    And that EVs are mostly rich boy's toy or enthusiasts are buying them.

    Average Joe concerned with commute isn't buying them. They aren't doing good at car rentals even. Hertz comes to mind.

    Mr. Musk must be given credit that he created such a FOMO that whole car industry went into panic and started building assembly lines.