Electric vehicle safety via crash test | Hacker News Reader

Electric vehicle safety via crash test

kbtx.com

33 pointsGabriel5452 comments

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...

> 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.

I would love that. At the very least, anyone with an at-fault accident should be barred from driving the heaviest vehicles.

> 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.

Like the rest of the world?

Australia car license limit: 4500kg for C (Car) class [0]

New Zealand Car license limit: 6000kg for Class 1 (Car) [1]

United Kingdom car license limit: 3500kg or 8250kg for class B [2]

France limit: 4250kg towing for class B [3]

Cavet: the above weights can be a vehicle or a combination vehicle weight depending on a bunch or intricate rules.

[0] https://www.transport.wa.gov.au/licensing/vehicle-classes.as...

[1] https://www.nzta.govt.nz/driver-licences/getting-a-licence/l...

[2] https://www.gov.uk/driving-licence-categories

[3] https://www.service-public.fr/particuliers/vosdroits/F2845?l...

4500kg is ~10,000lbs. That's about where the US draws the line, https://ai.fmcsa.dot.gov/NewEntrant/MC/Content.aspx?nav=Lice...

There are of course exceptions.

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.

Pretty much:

Tesla Model 3: 3,862 to 4,054 lbs

BMW i4: 4,553 to 5,049 lbs

Note that the model 3 and i4 are compacts (accord sized), the BMW 3 is a sub-compact. The i4 shares a chassis with the 4 series, which is

3,578 to 4,034 lbs

You really feel the extra pounds also, but I still like my i4.

I'm surprised the BMW 4 series is a compact, and a BMW 3 series is a sub-compact.

A 3 series is 185.4 in long, a 4 series is 187.7 in long. Does that make it jump from sub-compact to compact?

Apart from that, BMW wants to use its CLAR platform. Ever popped the hood of your BMW i4 and removed the 'engine cover'? What a load of wasted space there...

I had a loaner 3 once when my i4 was in the shop. It was so much narrow than my i4, at least when parking in my tight garage situation it was really noticeable. Only a couple inches I think. A civic is 70.9 inch wide compared to an accord that is 73.3 inches wide. The 3 series is wider than a civic while the 4 series is narrower than an accord, for what it’s worth. The diff between a compact and sub-compact isn’t that great.

Edit: it’s actually just an inch narrower. Goes to show how tight my parking situation is.

And the hazard detection in a Tesla means it's much more unlikely to crash in the first place, at any great speed.

Very debatable. A driver paying attention is much safer than any TSLA software, at least in my opinion. They've had plenty of recalls, dangerous bugs, and mislead/scam current/future customers in every way possible.

It's the 'paying attention' that is the problem.

The vehicle in the video looks like a Tesla Model 3 though.

The article points out the weight distribution matters too, perhaps the lower center of gravity of electric cars leads to greater penetration capability.

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.

> The battery used to power EVs creates a lower center of gravity and the front is a storage space instead of an engine compartment. These factors can all be seen in a crash test conducted at the RELLIS Campus

I cant brain the physics of both design details. Could you explain?

In this case it's a bad test thing.

The car impacted at a barrier splice which was not correctly joined. Barrier splices can come apart in the real world, but the fasteners will tear apart the sheet metal in the process. That splice gently deflected apart, like two sections of barrier were gently leaned against each other.

Two posts fall over on the initial impact, one on each side of the loose splice, without causing noticable specific damage to the car. The third post absolutely caved in the front end of the car before being violently bent down underneath, as properly anchored posts do in the real world.

This also isn't how this type of barrier is tested. "Barrier deflections listed below are results from crash tests with a 2,000 kg (4,400 lb) pickup truck traveling 100 km/h (62 mph), colliding with the rail at a 25-degree angle." More diverse testing done with seriousness would be a useful way to challenge if that standard continues to be appropriate, but this isn't it.

https://en.wikipedia.org/wiki/Traffic_barrier#Stiffness

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.

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?

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?

Maybe we should just have reasonable weight and size limits?

And power limits.

And bumper height compatibility.

And guardrails that respect motorcyclists body integrity.

So smaller EV batteries and less range and lower price. That seems ok to me. It's possible that advances in batteries will reduce battery weight, so replacing all the guardrails right away may not make sense. Difficult to predict battery future though. Maybe EV's need a cage at the front so the front end doesn't collapse so easily without an engine there?

Similar study in Nebraska, was discussed 8 months ago:

https://news.ycombinator.com/item?id=39215662

https://news.ycombinator.com/item?id=39641878

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.

Fairly common. A lot of things can happen during accidents, and cars sometimes run into guardrails at angles greater than 45 deg.

I’m just surprised they hold up to non-EV vehicles at a similar angle/speed. At 45 degrees, seems like most ICE cars would fly through them too, except for some of the more compact ones. But especially SUVs and trucks.

To me it seem reasonable middle ground. You get either 0 degree or 90 degree. That is glancing or head-on. 45 being between is not unreasonable option to set as coming at some repeatable angle. As you cannot test all collisions.

Head on crashes have already other methodology. Which covers some ground. After all you can only do limited amount of testing.

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.

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

Guardrail Damage Ahead

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.

They also don't get the clicks and eyeballs the way stories on EV do.

Ironically, it's only been the "huge truck with massive lift kit" type of people who have insisted that the weight of EVs makes them unusually dangerous killing machines versus ICE vehicles. It's plainly obvious that they don't actually care about safety, they just regurgitate anti-EV talking points because it supports their cultural needs to remain gas powered.

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.

Exactly. The weight of EVs is so overplayed, as if there was no difference already between a Corolla and a Camry.

Look at those gigantic utes\trucks Americans drive. Suddenly weight is only a problem if the car is electric?

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

Or make guardrails better. The EV center of gravity is a plus in lots of other situations.

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.

Huh? It sounds like it's a reason to re-design the guard rails. EVs aren't going away short of the discovery of some miracle fuel that doesn't generate greenhouse gasses. Even with a 100% hybrid fleet, the emissions will still continue to exacerbate climate change. We either figure out how to stop burning oil, or mother nature will take care of the problem (us) herself.

Where do you think the electricity to power EVs comes from?

Nuclear and Solar, at least for ours.

Residential rooftop solar in the US already produces enough energy to cover the charging of every EV currently on the road, and we're adding capacity each year faster than new EVs are consuming it, so that'll continue to be true.

Where do you think gasoline comes from?

Even if you collected 100% of tailpipe emissions EV’s would still be cleaner in the US.

Here (central CO) our energy supply is 33% renewable (increasing each year), 35% coal (phasing out, target 2030, NM coal plants we drew from already phased out back in 2020), 18% natural gas/oil, and 14% produced by others (no direct control). The benefit of shifting the energy from gas cars to electric is that as the grid converts to increasingly focus on renewables the overall emissions drop. Many people here are also putting in rooftop solar (this is a very sunny area, even through the winter though obviously with shorter days).

Mine's almost entirely hydro.

The power comes from a mix of natural gas, wind, solar, hydro, and coal. Coal is a shrinking component of the US power supply.

EVs are so efficient in using that power that even if you were to power entirely from coal, the CO2 produced with be no more than that produced by a 50mpg Hybrid. The US grid is not remotely as dirty as that.

Nuclear, wind, solar, and decreasingly coal.

Sibling comments have the answer. The math is that petrol powertrain is only 16% efficient, so coal power plant+long distance transmission+electric drivetrain still leads to less emissions.

https://thedriven.io/2024/01/31/electric-vehicles-use-half-t...

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.

I live in Seattle, a region of four million. Right now I see more new EVs on the road than new non-EVs. I think Tesla 3/Y are a plurality of vehicles I see in the city.

The number one selling car in the world is electric.

> Average Joe concerned with commute isn't buying them.

Eh? Costs me 3p/mile compared to 12p/mile on my old diesel. Pre-heated/defrosted automatically every morning. Fully charged and ready to go, and I don’t have to waste 15 minutes a week driving to the petrol station and refuelling. Best commuter car I’ve ever had.

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