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Comment by dmurray | Hacker News Reader

If you brake more aggressively, you will be involved in more accidents, but in fewer accidents that are considered your fault (courts and insurance companies will almost always find against the rear-ender).

You might also be involved in less serious accidents: a low or moderate speed rear end collision is safer overall than hitting a pedestrian, T-boning someone, or colliding at the higher speed from before braking.

That's a trade off that Waymo presumably know about, and are taking intentionally. It would be interesting to know what they prioritise: is it fewer overall deaths and injuries, or fewer accidents where they were determined to be at fault?

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>If you brake more aggressively, you will be involved in more accidents, but in fewer accidents that are considered your fault (courts and insurance companies will almost always find against the rear-ender).

I was talking to a kid once that was bragging about how his dad always got rear-ended, due to aggressive braking, but it was 'never his fault'. I was like "your dad is an asshole, that isn't something brag about."

That kid's dad is exactly why insurers push the OBD2 dongles and cell apps so hard.

The insurers want to know who those people are so they can jack their rate preemptively because there's a non-trivial chance that a) both parties in a collision have the same insurer b) the rear ended party's conduct is both indefensible and caught on camera and their insurer will wind up paying out anyway.

It's variation on a tired joke -

If you've been rear-ended, chances are the person behind you wasn't a very good driver. If you've been rear-ended 7 times, chances are that you are the person who isn't a very good driver.

Yes what do people do when behind somebody that's chronically slow and incompetent?

They tailgate them

I'd file tailgating under "incompetent". Being impatient is no excuse.

Insurers want those things to jack up all of our rates no matter how we drive. Give them enough data and they'll find something to justify screwing you over no matter how you drive.

Thats flat out wrong.

That’s not how insurers are permitted to set rates by state regulators and also it’s a good way to go out of business due to what’s known as adverse selection.

It's already been happening. https://www.nytimes.com/2024/06/09/technology/driver-scores-...

There's only one state in the US that prevents data collected from cars being used to increase your rates. Drive at night? Your rates go up. Drive "too often"? Your rates go up. Hit the breaks and successfully avoid hitting an animal or person suddenly running into the road? Your rates go up. Good luck counting on captured regulators to protect you. They did nothing to stop insurance companies from using records purchased from data brokers for ages. The EFF is calling on them to do more but don't expect much. https://www.eff.org/deeplinks/2023/06/steering-mobility-data...

Look, once again that’s not how rates work.

What you’re describing is segmentation, which is another way of saying geico charges the people without speeding tickets less than those with speeding tickets.

If ACME co decides to charge everyone the same, then the drivers without speeding tickets will go switch to geico leaving ACME holding the bag of speeders… and losing a ton of money since prices weren’t set for that.

Switch speeding tickets with hard breaking or whatever other thing correlated with accidents.

Also, as far as fairness goes, using actual driving behavior sound far better to me than using credit scores. But strangely I don’t see nearly the same level of complaints about that

You really can't control the behavior of the driver behind you, you just have to trust that they're going to do their job of not hitting things in front of them, just as you are. If humans are hitting things in front of them more often because they're concerned that the person behind them might not stop, that's probably indicative of a flaw in human driving behavior. The rules surrounding accident fault exist because of the individual responsibility assigned to driving behavior. If someone would have rear-ended a hesitant waymo, they would have rear-ended an equally hesitant human.

It obviously wouldn't be ethical for Waymo to brake aggressively just to catch out humans tailgating them too closely (at no risk to Waymo, after all, since the insurance of the car behind them will pay for damage and let's say they do this only when there are no human occupants). Even though it's a "flaw" in the tailgater's behaviour and even though he will have the responsibility assigned to him.

So is it ethical to brake aggressively to avoid a 1% chance of an accident up ahead? 5%? 0.1%?

This is a real life trolley problem, and the answer can't be as simple as "always brake, feel no remorse because it's the other driver's problem" even if that might be a good heuristic for a human to teach in driver's education.

That isn't just unethical, it is illegal. You can't intentionally cause an accident. The waymo would have the responsibility assigned to them if it was determined that was programmed that way intentionally.

It doesn't need to be intentionally programmed to cause an accident. The far more likely scenario is that it simply doesn't take into account what's behind them. It causes accidents by unintentional negligence, simply because nobody bothered to add a check.

Human drivers are taught to avoid scenarios like that. During drivers' lessons you will be taught to check your mirror before braking, and you will be taught to activate your alarm lights when there's a sudden stop on a highway to alert the drivers after you. Basic self-preservation makes it pretty clear that you don't want a car crashing into your rear.

Waymo doesn't need to care. If the other vehicle is considered at fault, their insurance is going to pay for your damages. It's at worst a minor inconvenience, so why bother spending engineering time on writing code to avoid it?

>Human drivers are taught to avoid scenarios like that. During drivers' lessons you will be taught to check your mirror before braking

If I'm going to crash into something I'm going to be slamming the brakes without checking my mirrors first.

Priorities. You should brake immediately to avoid an impending collision, of course.

OTOH, if you're driving and the light changes to yellow and you have room to stop, you should check your mirrors to see if there's a vehicle behind you that's unlikely to stop.

Additionally, in the impending collision decision, once you've taken initial action, you'll want to check on traffic to see if you have an option to evade the obstacle. And if you don't have an out, if there's a vehicle behind you and try to maintain space ahead and behind if possible.

>OTOH, if you're driving and the light changes to yellow and you have room to stop, you should check your mirrors to see if there's a vehicle behind you that's unlikely to stop.

If there's room to stop, then I'll still be braking immediately because braking immediately gives me the most time to brake, which makes the deceleration as gradual as possible and gives the person behind me the most time to react. I'm not sure what the alternative is supposed to be. Delay braking but having brake harder later? Gun it and try to run the yellow?

No, you should brake.

It sounds like people defending their terrible driving.

I had to retake a driver’s test recently and I’ve never heard of checking your mirrors before a yellow. What’s “a vehicle unlikely to stop” even mean? Like I can ascertain that in a second? The driver behind you is supposed to be traveling a minimum safe distance behind you for their reaction time. If they aren’t it’s 100% their problem.

> If they aren’t it’s 100% their problem.

It's your problem too if you stop for a yellow and they don't. They may be 100% at fault, but you're delayed at best, at worst may be injured and may not have a driveable car, and they may not carry insurance, so you may have a large, uncompensated loss.

By 'unlikely to stop', I really mean 'unlikely to stop without striking your vehicle if you were to stop', so things like following too closely, clearly not paying attention (which is hard to tell in a quick glance, but maybe you noticed their lack of attention before and haven't had time or space to make space), has a large vehicle that needs more room to stop, etc. I likely wouldn't stop on a fresh yellow if there was a trash truck following me closely, for example. Even at the extreme where I end up running a fresh red, it's more likely a better result than getting rear ended by a vehicle that's around 10x the weight of mine.

>By 'unlikely to stop', I really mean 'unlikely to stop without striking your vehicle if you were to stop', so things like following too closely, clearly not paying attention (which is hard to tell in a quick glance, but maybe you noticed their lack of attention before and haven't had time or space to make space), has a large vehicle that needs more room to stop, etc. I likely wouldn't stop on a fresh yellow if there was a trash truck following me closely, for example. Even at the extreme where I end up running a fresh red, it's more likely a better result than getting rear ended by a vehicle that's around 10x the weight of mine.

At best that's an argument for not slamming on the brakes on a yellow if you already know that someone is following you, not for you to waste precious seconds diverting your attention to your rear view mirror and trying to make a judgment call. In critical moments like that you really can't afford to divert your attention for whatever is happening behind you, because there could be important stuff happening in front of you as well (eg. the car in front decides to slam on the brakes). If you're really in a situation where you think you can't safely come to a stop because there's a truck tailgating you, you really should get yourself out of that situation rather than trying to run the next yellow.

> The far more likely scenario is that it simply doesn't take into account what's behind them.

Which would make it a bad driver.

Good luck extracting intention from the driving AI.

> (at no risk to Waymo, after all, since the insurance of the car behind them will pay for damage and let's say they do this only when there are no human occupants

That vehicle will still be taken out of rotation for repairs. In situations like that, does the insurance typically cover lost revenue as well? Otherwise there's still a ton of risk for Waymo if it's a typical deductible + repair costs. I genuinely know nothing about insuring a business like Waymo.

Depends on state law:

https://www.mwl-law.com/wp-content/uploads/2019/01/LOSS-OF-U...

But generally, yes, loss of use is generally something that courts recognize as a valid claim.

> you just have to trust that they're going to do their job of not hitting things in front of them, just as you are.

Thats a very human-centric viewpoint, understandably. A human driver can only see in one direction, and should be looking in the direction where things are happening the vast majority of the time. A self-driving car can see in all directions and in fact is looking in all directions at all times. Perhaps the rules will be updated at some point.

No, it's not a human-centric viewpoint. It's a physics centric viewpoint. When one vehicle follows another, the rear vehicle is on a collision course.

Human drivers are required to be aware of vehicles in all directions at all times.

You only need to train one person to drive to realize there's a really huge gulf between the bare minimum you're legally mandated to do when driving and what you should do to make driving less dangerous and less frequently displeasurable.

> A human driver can only see in one direction

Cars have mirrors. Any halfway-decent drivers' education will teach you to regularly check them, especially when you're about to brake.

It doesn’t really matter what’s behind you. If there is a danger in front of you and you don’t brake, it’s your fault, if you hit the brakes and someone rear ends you, it’s their fault for not keeping a safe braking distance.

You’d never design your system to intentionally be at fault.

Safe breaking distance is 2 seconds of travel between two and the car in front of you. In my experience almost no one ever follows this guidance and therefore yes, the rear-ender is always at fault.

I’m imagining some kind of future system where self driving cars are constantly scanning for tailgating, and when it happens, the number plate is logged and the data sold to insurance companies so they can adjust for high risk drivers.

Modern traffic radars have enough spatial and velocity resolution to apply a tailgating measurement. There are existing speed camera systems that can detect and ticket vehicles for tailgating, after a manual review of video and telemetry data (often just a quick glance and mouse click from a police officer).

There are relatively few jurisdictions that have a concrete quantitative definition of tailgating. So it's not yet widespread, but law enforcement certainly has the option available now.

The future will be that California will pass a law that mandates that newly manufuctured cars cannot tailgate at all, just like the one pending to beep at you when speeding.

In all serousiness, eventually, driving will be removed from humans.

How can you simultaneously check all the mirrors at the same time while also not looking away from the front?

> A human driver can only see in one direction

And it's usually in the direction of their phone. Even while driving.

You might not be able to control the behavior of the driver behind you, but you can certainly influence it. When there's someone close behind me and I know I'm approaching a situation that might require me to make a sudden stop, I often hold the brakes just enough to trigger the brake lights. This lets the person behind know to back off, or at least be ready.

I'm curious if Waymo does any sort of warning brake lights like that if chance of panic braking > 15% or something.

> "If you brake more aggressively, you will be involved in more accidents"

Is that statement based on evidence?

While that seems plausible, it also seems counter-intuitive to me. I suspect that many crashes happen because someone was afraid to apply maximum brakes, either out of fear that someone might hit them from behind, or simply due to being unfamiliar with braking hard.

It's true at some points in the parameter space, not at others. If you never brake at all, starting to brake more aggressively would be great!

Once you've tuned your parameters to be driving pretty safely and minimizing accidents, which is what Waymo is surely doing for some definition of "minimizing accidents", it must be true that every further parameter change involves a tradeoff like this.

Of you brake aggressively and someone rear ends you, could it not also be that the person behind was too close in the first place?

Not to be rude, but American drivers are not normally considered great, and San Francisco is number 7 on the list of cities you are most likely to get in an accident in the US.

https://www.forbes.com/advisor/legal/auto-accident/cities-mo...

The degree to which people tailgate is incredible. I live in a small town and people still act like it's going to take forever to get to where they are going.

One of 4 cars on a city street? Better try to push the car in front of you along, even if the other 2 in front of them are going the same speed.

Driving 2 miles on a 45 mph road? Better crowd the car in front of you that is already going 50 mph.

And then you get to the freeway where people think it's a great idea to try to push the car in front of you out of the way so you can weave through a little bit of traffic.

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