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Comment by dhx | Hacker News Reader

If a Model 3 decides to emergency brake without warning, can the driver still steer it to the shoulder of the highway, or are steering commands from the driver ignored?

I'm guessing the first car crashed into the rear of the Model 3, causing the Model 3 to spin out into another lane. Then a second car crashed into the Model 3 (probably side impact?) as it was now very dangerously exposed to oncoming traffic in the other lane. If the driver could have steered the vehicle during the emergency braking to the shoulder of the highway they'd likely still be alive. Unfortunately if the highway was heavily congested and this driver was sandwiched between vehicles on either side, there is probably nothing additional the driver could have done to improve the situation.

From the linked Facebook post there is the following comment:

My husband unfortunately was one of the drivers that struck the Tesla. He said the car in front of him almost hit the car so they swerved barely missing him and then there was the Tesla right there . He absolutely could not of stopped in time. It's a very traumatic situation. My husband is now dealing with survivors guilt and is taking it extremely hard. We are so very sorry this happened....I have no doubt that the gentleman that lost his life was loved by many and God help us all to find some strength to deal with the grief.

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> He said the car in front of him almost hit the car so they swerved barely missing him and then there was the Tesla right there.

This is not a criticism of the driver, because everyone does it, but one of my pet peeves is hardly anyone follows at a safe distance. Most of the time you can’t even if you want to because someone will merge in front of you with that much space.

So true!

> Most of the time you can’t even if you want to because someone will merge in front of you with that much space.

This annoys me so much. It creates a game theory situation where everybody has to drive like an asshole in order to avoid being cut off by assholes.

Seems like the game theory being applied there is a bit of prisoners dilemma. Is playing “asshole” the right move?

In California, unfortunately, the answer seems to be "yes." When I moved to the northeast US, drivers were more sane on highways.

When I moved to Boston, the first lesson I learned was any gap in front of me that can fit a car will soon have one there. I think it is big cities in general not just regions.

It is not big cities per se, it is any road that has surpassed carrying capacity. Obviously, this will be seen more in areas more densely populated with cars relative to road capacity.

If you drive in south or east Asia, you will see what naturally happens when the number of vehicles on the path greatly exceed the capacity of the path traveling at a certain speed. You can basically model it as fluid dynamics at a certain point in places like Mumbai and Bangkok.

Frankly it's fine to create enough gap that people are passing in front of you.. My response is usually to widen the gap even more. It actually has the effect of helping to smooth traffic, reducing traffic jams.

> It actually has the effect of helping to smooth traffic, reducing traffic jams.

I hear this a lot from people who practice this sort of driving, but don't the simulations suggest that the opposite is true, traffic actually improves when drivers are more aggressive?

Having cars be "aggressive" in this context basically means they flow into the voids more readily.

An example would be moving left into a "this would be an impolite move in any other context" sized cap between two cars to in order to let someone merge and then getting right back out of the lane.

https://www.youtube.com/watch?v=iHzzSao6ypE

You are also reducing throughput, and causing more congestion behind you. There is no having our cake and eating it too. Once a road hits maximum capacity at the safest distance gaps between cars, the only way to increase the road capacity is to reduce the distance gaps between cars.

In addition to increasing the gap, you have to drive steadily, with no braking. This makes you become the most predictable car on the road, people behind you can follow steadily instead of constantly accelerating & braking. This leads to reduced congestion.

This CGP video covers some of this https://www.youtube.com/watch?v=iHzzSao6ypE

There is no steady in high congestion areas with lots of on and off ramps. The rules are nice when there is no congestion and plenty of room to spread out, but the problems are inevitable at rush times or at chokepoints.

Not all congestion are created by those chokepoints. It's created because someone at some point hit the brakes, and then cars behind get into a pattern of accelerating & braking constantly until the congestion resolves. Steady driving with lots of gaps helps resolve this faster and prevent congestion in general.

unless you do this in the left lane or something, it probably doesn't change throughput that much or at all. A major cause of traffic jams is cascades of braking, so leaving a safe distance allows for coasting instead of overreacting to brake lights, and prevents a traffic jam. You can get higher capacity temporarily, but eventually by reducing distance, you just cause a jam that destroys throughput.

Until you realize being cut off doesn’t actually impact you much so you play a much safer game of giving everyone a wide enough berth to act like an idiot and not ruin your day. Driving habits are extremely psychologically interesting, from road rage at a stranger who did something you didn’t like to people feeling compelled, and indeed proud, of unsafe driving habits that put multiple lives at risk to save a couple minutes on a trip. An argument could be made that curing these tendencies would stand to save more lives then almost any other mass behavioral correction (saving maybe dietary choices).

> Until you realize being cut off doesn’t actually impact you much

I keep a long distance, and I drive fast. Germany, so fast means actually fast. My large safety margin means I have to keep braking because slower cars move past me and into my safety margin. Then, once the original blockage in front of me is cleared, I have to pass all those slower idiots who just overtook me again.

If driving wasn’t such a rare occurrence (usually 3-4 times a year) for me, I’d probably stop keeping a large safety distance like every other asshole.

Granted, race car drivers who think distance is measured in centimeters are even worse.

Absolutely. In the context of high way driving especially with its high speeds, the slight slowing down to maintain follow distance even if people were constantly moving in is negligible to the overall trip time, and it’s highway driving where that follow distance is the most critical to saving lives.

If people sat down with the numbers and realized how little that slight slowing down in the moment someone moves in front of them impacts their trip time, how little it matters to the original trip time that someone passed them, the roads would be a lot safer, less stressful, and faster overall.

If everyone slowed down, there would be far more congestion backing up due to reducing the throughput of the road.

I would argue that the people driving at distances closer to the car in front of them are reducing congestion by increasing the throughput of the road. Obviously this is mitigated by decreased throughput due to increased probability of collisions.

But if EVERYONE drove such that they could fully stop if the car in front do them fully stopped, you would have a public uproar over how much backed up traffic there was.

There road is basically constantly in flux and politicians could enforce minimum driving distances very easily with cameras and drive down collisions, but it would be massively unpopular and they would get voted out immediately. I presume that is why we already do not have speed cameras in the US.

It would be trivial to fine everyone breaking the speed limits. Or even driving too close to each other. For a tolled road, you can get go back however many years you want and retroactively fine people for going past the speed limit based on toll time stamps. But I figure the lack of this happening means the public wants to make this risk vs convenience trade off.

As soon as someone crashes, that congestion is going to go way up. In very specific conditions where a road is congested already, slowing down does cause a cascading effect, BUT, if everyone is already maintaining a proper follow distance, it takes longer for the road to reach max congestion in the first place. Consider it like a bunch of springs all lined up spring wise; if you have the same number of springs, and you’re trying to insert a new spring (someone is merging), the springs which were less compressed will more easily accept a new spring, while the ones where are already compressed will experience more strain.

And imo, I’d rather be going slow because “we’re going the follow distance” than going slow because “someone went too fast in an unsafe condition and crashed (or worse)”. In the face of sheer car volume, we’re all going slow(er, though note that we’re usually still getting there faster than a horse would have) pretty much no matter what, might as well be safe while doing it.

> BUT, if everyone is already maintaining a proper follow distance, it takes longer for the road to reach max congestion in the first place.

I do not think this is a realistic model of the way roads work due to rush hours and sudden increases in demand. The ideal rules are great for when demand ebbs and flows gradually, but things change when everyone wants to be on the road between 8AM and 8:30AM. Then, you can have all the protocols you want, but the system has reached max capacity and there is no avoiding that other than dealing with the consequences (congestion -> stop and go traffic -> gridlock) and of course a collision or two.

I am not saying this justifies driving like a maniac and cutting people off. I simply expect people to act a certain way over the boundary conditions of a situation are approached, and I will not expect it to be the same as how they act when we are not pushing the limits.

There are several major traffic accidents in Atlanta every morning during rush hour on the most important arteries. Most of these are probably caused by tailgating or aggressive behavior during merging. They turn a 30 minute commute into a 90 minute commute if any lanes remain open.

I can’t imagine that the downstream effects of maintaining a safe following distance and permitting people to merge would cause anywhere near the inconvenience of these daily, destructive events.

There are varying levels of safe driving distance. You can drive close enough to the car in front of you such that you can slow down quickly enough if they slow down from 70mph to 50mph, or if they slow down 70mph to 10mph, but gradually.

You can also drive further back such that you can slow down if the car in front slams on their brake and comes to a complete stop. This is the distance I am referring to which would be politically unpalatable to enforce.

I agree that people weaving in and out and tailgating and cutting people off are doing more harm than justified, but it all starts getting murky once the road hits capacity limits and people start trying to figure out the best way to optimize their travel times. Eventually, with enough congestion, the situation will deteriorate from stop and go traffic to crawling traffic to downtown Manahattan to Delhi and so on.

> it all starts getting murky once the road hits capacity limits and people start trying to figure out the best way to optimize their travel times.

that actually happens sooner when everyone is crawling up each other's asses.

once you get that first compression wave due to tailgaters slamming on their brakes then you've started the traffic jam.

I think that's an extremely suspect hypothesis. Most congestion is caused by:

- Construction

- Accidents

- Directly counter to your point: people driving like assholes and cutting others off or forcing others to take abrupt maneuvers that then cascade through the tightly packed traffic

Slow speeds and ample space do not cause congestion, changes in the flow of traffic do, and usually those are caused by people following too close and making sudden maneuvers. If enough space is given and the flow of traffic is not disrupted you could go as fast as you want with as many cars as you want and not experience congestion.

It's the mentality you're espousing here that I find so fascinating about road travel. There appears to be such dissonance that one will justify speeding or tailing or road rage in all kinds of ways.

Too many cars on a certain section of the road at a certain point in time is congestion. This can be caused by many things, such as roadwork, collisions, but more often than not, it is simply a result of lots of people wanting to drive in the same direction on the same road at the same time. Aka rush hour.

I am not justifying road rage or tailgating. I am explaining that it is inevitable once the road gets close to carrying capacity, which can only be increased in the immediate term by driving faster and/or decreasing the distance of gaps between cars.

You say you're not justifying tailgating, but it sounds like your prescription for rush hour is exactly that.

I suppose there are different characteristics in different types of congestion. Stop and go congestion is usually caused by disruptions to the flow of traffic, while slower than usual congestion is indeed caused by over-capacity as you indicate. Just moving slower would be all such times would experience if not for people tailing and cutting others off, leading to the stopping part.

Even moving slower will not prevent stop and go traffic if the road has reached its capacity, due to the various different accelerations and decelerations of cars.

My overarching point is something like this video:

https://m.youtube.com/watch?v=Suugn-p5C1M

There simply is not a way to avoid the consequences of being near or above a road’s capacity. Of course, I recommend everyone to play it safe and stay far enough back to avoid any liability of being too close to the car in front. But the reality is we make lots of calculations and choices in driving and at various times, we choose farther distances and other times nearer distances (even though we know it is riskier) and these collective decisions will propagate down through the whole road.

> due to the various different accelerations and decelerations of cars.

Right, changes to the flow of traffic.

> There simply is not a way to avoid the consequences of being near or above a road’s capacity.

I agree, that is a valid bullet point. But that is certainly not the only cause of congestion, and driving aggressively in congestion and attempting to justify it by keeping the roads clearer doesn't hold a lot of water I don't think.

But I see you're saying you're not advocating unsafe driving so that's good, and I take your greater point, thanks for expounding on it.

You're doing static analysis on a dynamic situation. The biggest issue with overcapacity is the start of compression waves of traffic, which are generated much sooner by tailgaters slamming on their brakes in a panic with each following vehicle having to brake harder than the one in front, eventually coming to a complete stop (or just causing an accident).

> If everyone slowed down, there would be far more congestion backing up due to reducing the throughput of the road.

This isn't true. The greater the following distance, the more time a driver has to respond. More time to respond means fewer and gentler inputs. In turn, this reduces propagation to following vehicles, and as a result traffic moves faster. It's the difference between turbulent and laminar flow.

> I figure the lack of this happening means the public wants to make this risk vs convenience trade off.

Joe Public has never sat down to think this through, nor is he qualified to do so.

Joe Public decides this by demanding their politicians to not enforce speed limits. A campaign would be dead in the water the second it talks about having cops issue more speeding fines or install speed cameras or using toll times stamps to issue fines. The US public is not sufficiently scared of injury or death from collisions to make it a political priority.

> In turn, this reduces propagation to following vehicles, and as a result traffic moves faster. It's the difference between turbulent and laminar flow.

And in turn, this decreases the rate at which vehicles enter the highway, which backs up onto the streets that lead to the highway.

This is another reason why I think of commuting as a religion. Where else would you see such zeal and self-righteous behavior?

You can count lines at the side of the road? I’ve never found it particularly hard to silently count to two. If someone merges in front we just slow down a bit and repeat the excercise.

It's not the counting that's hard. it's that others will merge in front of you constantly.

Also as you adjust to increase the gap in front of you, the person behind starts tailgating, if they were not already.

In my experience, tailgaters are never satisfied by the speed of the car in front of them. The only good play is to leave enough space in front to stop without getting rear-ended.

In Atlanta, people will tailgate in spite of a wide open lane to the left and the driver in front going the speed of the road. I’m not going to tailgate the person in front of me just because the person behind me is tailgating.

Yeah, tailgating the person in front of me because the person behind me is tailgating has always felt like a: "well, now I have two problems" kind of situation.

If someone is tailgating me, I purposefully slow down, to 10-15% below the speed limit. If someone is determined to crash into my car, I prefer them to do so at as low a speed as I can get.

This does happen, but I find it doesn't result in me getting to my destination any slower.

If someone merges close in front of me, I reduce my speed by 5 mph or so for as long as I need, probably usually around 10-20 seconds, until there's an adequate gap again. Often someone will pull into that gap within a few mins, and I do the same thing. Overall it reduces my average speed by an imperceptible amount. It might add up to a couple minutes over a several hour journey, but I take that as worth it for being less likely to rear end someone.

Additionally, it really only happens in dense traffic when in the outside lane to exit the highway. When you're in the fastest moving lane and keeping up with traffic, few drivers are going to over/undertake you just to get into the gap. More typically they'll overtake the car in front of you too so it's not a problem.

Admittedly most of my driving is in UK and NW Europe rather than the US. US drivers seem a lot more suicidal and US highways tend to be less predictable by design.

I drove a rental a year or so ago, and it had adaptive cruise control. This is where it would be like cruise control, except it would slow down if a car in front of you was going slower, and adjust the car speed to match their speed.

I'd never seen this before. I found that I couldn't really use it, because the distance you could set for it to follow the car in front of you was too close for my taste. I found you could decrease the distance by quite a bit, but I wasn't able to increase it to what I wanted.

Which brand was it? The ones I've seen adapt to the speed, so 2 bars in the cruise control adjustment means a certain distance at 100 km/h, and a longer distance at 130.

Everyone does it because the law isn't enforced, and because nobody is following the law enforcing it is seen as unreasonable.

On the spectrum between charging people for involuntary manslaughter for cases like this and saying "there's nothing they could have done" we are very far on the latter part of the spectrum.

My car and that of my wife warn audibly, if the distance to the car in front is below a configurable distance. I have to actively ignore that wanring.

Same here. And it will display a constant icon on both the console and my HUD if I have insufficient stopping distance.

I saw someone was downvoted for calling you an asshole. I guess that doesn't really follow the spirit of HN, but it's crazy to me how much we have normalized driving dangerously as a society.

We have seemingly decided it's perfectly fine to drive in a way that puts others at risk of death or serious injury. It's to the point that if you call someone out on it, like the other commenter did, you're the one in the wrong. Yet they were just calling out a person for putting other people's lives at risk. We should be condemning driving like this, just like we condemn many other activities that put other's lives at risk.

There is some ambiguity in jhoechtl's comment. It isn't clear if they are saying they choose to routinely ignore the warning, or if they are saying that they would have to ignore the warning in order to routinely follow too closely and end up in a situation like was being discussed.

One of the site guidelines is to interpret a comment in the best possible way, so I am choosing to interpret it as the latter.

The latter was the first way I read it. It is a common expression.

Sure there is. Every driver has a duty to be able to stop in assured clear distance and to maintain proper lookout. The vehicle that struck the Tesla, breached these duties and is the proximate cause of the loss. Tesla/the driver of the Tesla, shares some contributory negligence for assumption of risk. 80% liability on the rear ending vehicle and 20%on the Tesla.

I once took a defensive driving class, and the teacher's primary point throughout the whole thing is the only area of your car you have control over is the area in front of you. You obviously can't control whether people are beside you or not. You can't stop the person behind you from tailgating. All you can really do is ensure you have adequate space in front of you to respond to events.

My driver's ed teacher said a similar thing about right of way - you never /have/ right of way, you are given it. I try to drive defensively, but it's a challenge when others are able to choose not to in ways that affect my driving.

That should be "priority". Right of way is about laws allowing walkers to cross private lands etc.

You don't have complete control of what's behind/beside you but you have some control.

Maintaining situational awareness of these areas and adjusting your behavior to coax other traffic to behave in a way that is best/easiest/safest/whatever-ist for everyone is a prerequisite to being a "good" driver IMO.

Unless it is just heavy traffic, I constantly tweak my speed and following distance to avoid driving in other driver's blind spots and ideally not be driving beside them.

>This is not a criticism of the driver, because everyone does it,

It is a valid criticism of the driver and not everyone does it. It is a major problem that so many people treat safe following distances as great places to cut someone off to save .05 seconds on their commute while risking the lives of others.

To reply to your first question: if the car decides to emergency brake, you can still override it by pressing the accelerator. In my experience, the braking that happens is "hard" but no more hard than you would do yourself if something suddenly appeared in your drive path, and if you are paying attention you can press the accelerator within a second or so. If the person behind you has adequate following distance it shouldn't be a problem.

If the car loses power entirely then it gives you a few seconds warning in which you may or may not be able to cross to the shoulder before the car coasts to a stop. In this scenario the braking is not "hard", but obviously there is no real way to recover and you'll need to get towed.

I have not experienced any scenario where the car does not respond to steering or acceleration commands when it was physically able to do so.

Self-reply to add: despite (occasionally) experiencing phantom braking and my wife once experiencing the "loss of power" scenario due to a defective drive unit, I'm still very happy with the Tesla overall. In my experience it is the best car I've owned despite the flaws that seem to disproportionately make the headlines.

if it emergency brakes, does steering still work or not until you accelerate?

It does work, yes.

Yes - a slight nudge on the steering wheel or pedals deactivates autopilot. You always have full control like when driving like normal.

One should therefore always have the hands on the wheel and feet by the pedals and be ready to drive.

> slight nudge

To clarify, this only applies if the car doesn't think you're about to exit the lane. It will momentarily fight you, and it will take more than a slight nudge to override it.

> if something suddenly appeared in your drive path, and if you are paying attention you can press the accelerator within a second or so.

So if something appears in your path, the right course of action is to accelerate into it?

within a second or so is great but not if you have 1/4 second time to respond.

> If the person behind you has adequate following distance it shouldn't be a problem.

Nice assumption.

> If the car loses power entirely then it gives you a few seconds warning in which you may or may not be able to cross to the shoulder before the car coasts to a stop.

may or may not indeed.

> So if something appears in your path, the right course of action is to accelerate into it?

Not into it, but around it – if possible, of course. It's something you learn in motorcycle school, for example.

The idea is that a motorcycle is harder to maneuver while under hard braking, so you have a better chance of avoiding the obstacle or falling by going around it.

>> If the person behind you has adequate following distance it shouldn't be a problem.

> Nice assumption.

Of course. This also feeds into the above. As in, not only do you have to stop, but also to make sure that the person following you will stop without hitting you.

> So if something appears in your path, the right course of action is to accelerate into it?

>> ...the braking that happens is "hard" but no more hard than you would do yourself if something suddenly appeared in your drive path...

parent post was just giving a comparison to the deceleration-snap experienced during phantom braking, and saying in the event of a phantom brake, you can cancel the event by tapping the gas (battery?) pedal

> So if something appears in your path, the right course of action is to accelerate into it?

You mis-parsed what I said here. My sentence was probably too long. Let me try using shorter ones. Say you are driving. Suddenly a squirrel appears on the road 50m away. You apply brakes "hard" to avoid hitting it. This amount of braking is what the car does. You can still press the accelerator. The accelerator works as expected, cancelling the software's braking.

> if you have 1/4 second time to respond.

Under what circumstances would you have this short amount of time? IMO only if somebody is following you too closely. Again, remove the software from the equation and insert the aforementioned squirrel. You brake hard for it. The person behind rear-ends you because they were following too closely. Who is at fault?

> Nice assumption

Thank you

> He absolutely could not of stopped in time.

Somebody (not necessarily the husband) was driving too close to the car in front. You should have enough time to see the car stopping and stop yourself. A 2 second gap at 60mph is 178 feet. A second to react and that still gives you 88 feet to slow down in before you even get to the point where the Tesla started to slow, reducing the impact speed to far lower -- not enough that should kill anyone.

crowded expressways have a way of filling gaps

Not necessarily the case.

Friend of mine was on the middle lane on the motorway when somebody switched on to his lane and braked hard.

He crashed against but wasn't deemed at fault by insurance.

Not saying that this is what happened, btw.

> If a Model 3 decides to emergency brake without warning, can the driver still steer it to the shoulder of the highway, or are steering commands from the driver ignored?

Yes - a slight nudge on the pedals or steering wheel will deactivate autopilot and let you drive like normal.

After you've spent another second (and 150 feet) fighting the AP to say, "no, I'm not drifting out of my lane, this is intentional".

150 feet a second? Where are you driving where you're doing that speed and changing lanes and are concerned about 150 feet?

Why doesn't the lane detection deactivate when you indicate?

Sure, maybe 100f/s.

> He said the car in front of him almost hit the car so they swerved barely missing him and then there was the Tesla right there .

This is how my friend lost all 4 wheels on his car. Following too close to react to stuff that the vehicle in front of him could. Hit the raised island for a slip lane when someone swerved out of the right turn lane at the last minute.

So, the car in front was able to swerve, but from 2 cars back, he couldn’t and ended up killing a person. Somebody wasn’t paying attention. Not they he’s unique in this, but his statement is baloney.

Even at a save distance, if the car was at a complete standstill, thats something completely unexpected on the highway. Having to react in such a short timeframe is close to impossible for a human, even when you keep a "safe distance"

The "safe distance" is only "safe" if all the traffic is moving at least.

I've seen cars at a complete standstill on the highway more than once. It's fair to say it is unusual but it should be fully expected, IMO.

I don't understand the scare quotes around safe distance here. Maintaining safe distance (and the implied safe speed and open eyes) absolutely would help in these situations.

Car in front saw the car before them suddenly start to brake, but Tesla was still moving fast enough to get out of the way. Which revealed an almost stationary car to the person behind, whom was still driving 70mph.

I can see how that is hard to react to.

I wasn’t sure how hard though, so I did a thought experiment.

Say there is 50m between each car, and they’re all driving 25m/s. First car starts braking at 5ms. After one second the distance between 1 and 2 is 45m. After two seconds, 35m. After 3s, 20m, and the car is evading. After 4s, car 2 is passing by 1, whom is now moving at only 5m/s. Car 1 is finally revealed to car 3, who now has a maximum of two seconds to do something before it crosses the 50m gap.

And that’s assuming an adequate gap. They were likely closer.

Have you ever had someone in front of you swerve out of the way, leaving you facing a stopped car? It's exciting, let me tell you. The idea of safe following distance is predicated on the car in front of you not being able to defy physics when they stop, presumably their braking power is similar to yours.

Yes. But because I was following at a safe distance from the car in front, that gave me adequate time to slow down and stop without hitting the stopped car.

Safe following distance isn't predicated on defying physics, it means assume the car in front might stop dead for any reason - hitting an unseen obstacle, swerving to reveal an obstacle, sudden mechanical failure, animal collision, whatever. The distance you need to react and stop is around 100 metres at 70mph. Therefore, that's the distance you should keep from the car in front.

As a bonus, it gives any tailgaters more time to notice you're slowing down too. Hopefully this means you're less likely to get pancaked between two cars.

>Safe following distance isn't predicated on defying physics, it means assume the car in front might stop dead for any reason

No, it's based on assuming the car in front might brake at standard non-physics-defying rates at any time. The 'safe' following distances that are advised don't allow for encountering stationary objects. That's why they're called following distances, as in, you're following another vehicle that obeys the laws of physics.

But that Tesla didn't defy physics. Nor did it fall out of the sky. It braked and slowed like any other car.

Maybe there truly wasn't enough time to completely avoid a crash. But there should have been enough time to avoid a serious (deadly) crash.

>It braked and slowed like any other car.

Imagine you're following - at a safe distance - a vehicle. The driver of the vehicle you're following doesn't notice that the car ahead of them is emergency braking. They notice at the last second and swerve around it to avoid a collision.

You are then face to face with a nearly-stationary object which was concealed from you by the vehicle ahead of you.

From your perspective, it fell from the sky. If you don't swerve, a collision is unavoidable.

I think we are in agreement with the the situation, I just disagree and think you're either driving too fast or following too close. Your logic leads to pile ups, as in the event of a pile up, a car stops dead unexpectedly infront of you and you have nowhere to swerve.

I can't speak for the USA, but in the UK, if someone swerves and you rear end a stationary object, you are at fault. Indeed if you rear end another vehicle, you are nearly always at fault (unless e.g. they pulled in front of you then immediately slammed the brakes).

For stopping distances, this is what we are taught in the UK (rule 126): https://www.gov.uk/guidance/the-highway-code/general-rules-t...

Stopping distance at 70mph is about 100m and "The safe rule is never to get closer than the overall stopping distance". This is a minimum - in adverse conditions the distance should be even greater.

This means when you see the stationary object, you're about 100m away, which is adequate time to stop IF you're paying attention and your car is well maintained (we have annual MOTs to ensure this).

I don't know about the USA, but in the UK our stopping distances assume the car might become stationary at any point. That is, they are actually stopping distances - not following distances. If you follow closer than that on your test, you will fail.

Frankly, I can never imagine seeing an empty football field worth of space between two cars on a busy freeway. Even if you attempt to create such a space, other drivers will fill it.

This assertion about following distance feels purely theoretical for busy freeways.

Caveat: I drive in the UK so driving quality may be different here. I always maintain adequate stopping distances on busy motorways. People do fill those gaps occasionally and it does result in me driving slightly slower on average by a couple mph maybe, but it's perfectly possible to maintain a gap.

A lot of experienced drivers here claim it's impossible too, but there's a good way to know that it's not: on your driving test, you'll fail for following too closely, so most people manage to keep an adequate stopping distance for the test. Following closely is usually a habit picked up when someone becomes a more confident driver.

The real reason is probably people don't want to take the tiny average speed hit or find it unfair that they keep letting people in.

Sure. But, in this case, there were three+ cars. The Tesla that stopped, the car immediately behind the Tesla swerved, and the third car ran into the Tesla.

The driver of the third car claims there was nothing he could do. That's baloney, as the car that was EVEN CLOSER to the stopped Tesla was able to react. Fact is, he was following too close and/or not paying attention, and crashed.

If the driver of car 3 could not see past car 2, and car 2 hadn't realised the Tesla had stopped, and instead swerved out the say 1 second / 90 feet (assume 60mph) before collision, that would give car 2 traveling at a reasonable gap no more than 3 seconds / 270 feet to recognise what was going on and stop.

Should have recognised something odd (a broken down car) within 1.5 seconds, leaving 1.5 seconds to slow down.

Applying brakes from 60mph would mean you'd still be traveling over 40mph when you hit the back of the car.

Thus you need to give more than 2 seconds if you can't see beyond the car in front

I agree that the third car is almost certainly at fault. "Didn't have time to stop" is nonsense in every case except if some idiot cuts into your lane within your safe stopping distance and then immediately brakes.

Drivers need to think of every vehicle as being in a moving block[1] signalling system with each block being ~290m long (actual vehicle in the middle of this block) in wet conditions at 110kmh-1[2] and ~230m long in dry conditions at 110kmh-1[2]. No vehicle should ever enter another vehicles moving block. Obviously the type of vehicle, tires, road surface material, etc can reduce (or extend) those required block lengths, but you generally have to assume worst case scenario because how are you to know whether another vehicle has bald tires or is operated by a person who is fatigued or distracted and taking much longer to respond than they should.

[1] https://en.wikipedia.org/wiki/Moving_block

[2] https://www.qld.gov.au/transport/safety/road-safety/driving-...

The question is whether the accident would still have happened, if the second car drove a Tesla, also with the autopilot engaged?

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