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by Swizec 3998 days ago
> Consider another problem the vehicle already solves. The AV wisely yields to those running a red light, even though the AV has the right of way. If it didn't, but was instead frequently t-boned... Google could technically still say its vehicle "never caused an accident," right? It'd never be at fault for these, but the AVs are still designed to avoid them anyway. Is this inconsistent with a choice not to avoid rear end collisions at intersections?

This is called defensive driving. You as a human are supposed to avoid getting killed even in cases where you aren't legally liable. This includes making sure the intersection is clear before going in. It includes checking if anyone is coming down the wrong way of a one way street before going in or crossing it. It involves something as simple as making sure "right lane must turn" actually turned before someone magically appears out of your blind spot.

And, importantly, it also includes knowing what's behind you as much as knowing what's in front of you. If you see someone is going to rear-end you, you should at the very least step off the brake to make the collision less violent. If possible accelerate forward.

And I know this isn't possible [/practical] in most american cars because they're automatics, but don't hold the brake when you're standing still. It makes potential rear-endings work out better. And never turn the wheel before you intend to turn. If you get rear-ended you could get pushed into oncoming traffic.

All this is to say that while only one vehicle is to blame for a collision, two vehicles are responsible. (unless you hit a tree or some other static barrier, a tree cannot drive defensively)

Or, more bluntly, it might be the other person's fault, but you're the one who's dead.

3 comments

I've been taught to always hold the break when at a stop light. If you get rear-ended, you won't roll into the intersection. Also, always hold the steering wheel, so you keep control if you get rear-ended.
I was taught to engage the hand brake when stopping at a junction or lights for this reason, a rear end impact would generally be at low speed compared to the speed of the potentail traffic in the crossing lane.
I've always assumed you can press the brake post fact to prevent rolling into an intersection, which I assumed was better than absorbing a lot of G-force.

Fundamentally, I think, if the impact is too strong for you to be able to react in time to brake before rolling too far, you would have rolled into the intersection despite holding the brake. Except it would be a skid not a roll.

I could be wrong, obviously.

Your vehicle will accelerate less (fewer Gs) if your brakes are on.
The energy is still going to have to go somewhere.

Some of it will go into the crumple zones, the rest will go into burning rubber and throwing passengers against their restraints.

The question is whether a person is better able to withstand being pushed from the back with rapid acceleration, or absorbing the energy of a collision.

I do not have an answer, but I'm very interested where I could find one.

You mention whiplash in another comment. Wouldn't you avoid most whiplash with a properly configured headrest?

Yes, that is what the crumple zones are for!

Not sure what you mean by this: > pushed from the back with rapid acceleration, or absorbing the energy of a collision. The occupants don't have to absorb the impact if the crumple zones take it!

I guess decent seats will do a lot to protect the occupants. A few years back I was a rear-seat-passenger in one of these https://upload.wikimedia.org/wikipedia/commons/5/50/Nissan_M... when it was rear-ended. Luckily our driver WAS on the brake and didn't go forward into the cars in front - unlike the car behind us and the car behind them and the car behind them! (I forget exactly how many cars were involved but it needn't have been as many).

It's not about impact being strong. The surprise of the impact will severely slow down your reaction. By the time you've reacted, it's probably too late.
> You as a human are supposed to avoid getting killed even in cases where you aren't legally liable.

The bar is much higher than that. You are supposed to protect others, not just yourself, and including people who are at fault.

If a pedestrian is jaywalking and you provably have plenty of time and ability to avoid them, but you strike and kill them, you are definitely guilty of something like manslaughter. Although people somethings believe otherwise, the law (and morality) do not have the property that initial minor transgressions by one party absolve the other party of all fault in a resulting interaction.

Sometimes it really is impossible, I was involved with a case where the victim literally ran across the street, hidden by a bus stop panel. Nobody saw nobody, driver well below speed limits.
DO hold the brake if you are about to be rear ended. It results in less acceleration, and you are less likely to be projected into an obstacle.
Doesn't this depend on what is in front of you? If you can safely move forward, wouldn't not holding the brake be better?
No. Rapid acceleration from being rear-ended causes whiplash. Having brakes on reduces the initial acceleration.
In modern bucket seats the risk of whiplash injury is incredibly minimal. Your head doesn't have the distance to travel far enough to hurt your neck. On the other hand, standing on the brake will cause both vehicles more damage and cause the other car to decelerate more quickly, causing the occupants to experience more acceleration in a direction in which the restraints are less effective (getting pressed into seat-belts and airbags hurt more than getting pressed into a seat).

Standing on the brake is simply shifting the energy around at the expense of the other party

If there is a car in front of you, not holding the brake is shifting energy at their expense!
Assuming an intersection, wouldn't it be better to be rear-ended hard than having a vehicle slam into the driver's side door?
Yep, which is why I think it depends on what's in front of you. A human probably doesn't have enough time to analyze the situation and determine whether or not they could do better than holding down the brake. A computer can probably do better in some situations.
Well that depends in where you want the momentum to go and how rapidly do you want to and can afford to dissipate it, does it not?

I mean, if the impact is strong enough, you'll be sent flying whether you are or aren't holding the brakes. Just that if you're not, your steering wheel is still going to steer.

The kind of things I wish driving school could teach you. I don't know how, a set of busted cars on a driving loop with mild collision so you'd know what it feels and how to react. Kind like wet roads and collision avoidance classes.