In a multi-car pileup, the car immediately in front of you literally stops in an instant, much faster than if it were to fully hit the brakes. It's much faster than any driver could realistically expect. It can happen so fast, you may not even see brake lights turn on. It's why these pileups can get so surprisingly large.

Indeed. This is why you can't drive around just looking at the back of the car in front of you, you need to look way down the road. The distance to the car in front of you needs to be large enough that you can react if that driver steps on the brake, but will never be enough should they impact a stationary object. You need to see stuff like that much earlier, and if you can't, you're driving too fast.

I'm constantly baffled that these pileups happen, since it's obvious these people were driving much, much faster than is justifiable under the conditions. They should all lose their licenses.

They're so rare that most drivers can't even imagine it happening to them. Combined with the fact that most drivers don't even understand what it is they should look for.

Really? The need to look far down the road is literally the first thing that comes up if you google "where should I look when driving":

* In order to avoid last minute moves and spot possible traffic hazards, you should always look down the road ahead of your vehicle.

* Your attention should be focused on the road ahead, following your intended path of travel. It would be best if you allowed a visual lead-time of at least 20-30 seconds.

* Scanning the road ahead while you’re driving is one of the best safety tips you can employ when you’re behind the wheel! Generally speaking, you should look ahead 15 to 20 seconds or an eighth of a mile when driving in the city and 20 to 30 seconds or about a quarter of a mile on the highway.

etc, etc.

Normalisation of deviation.

When a person first gets their licence they may google the content you describe. Then they drive to work and home - down the freeway - every day for years.

They quickly learn that leaving too much space in front means people keep jamming in front of them. And the vehicle in front is the one you react most to - when it slows down or speeds up a little. So they pay attention to the car in front rather than down the road. Why look down the road? It hasn't been relevant for XYZ hours of driving so far...

Eventually they confirm to the norms of traffic. And why not? They haven't seen an accident in ages and if they have, they likely drove past it after the fact without knowing how the accident happened and believing it to be a "freak thing". Thus the deviation from what they should do is rationalised and then normalised through daily use.

Then an accident happens and a multi-vehicle pile up occurs because the "norms of traffic" are NOT what people should be doing.

Sadly most people do that. While continuing to believe that their initial conscientiousness (first impressions!) - since slackened/eroded - means they are an above average driver.

And I too am subject to this human behaviour as much as I try to be conscientious about it. I know I will have some bad habits learned in similar fashion. But I don't know what they are because I have rationalised all my actions to myself. I should go do some training again...

Just to quantify this, the shortest 60-0 stopping distance for a "consumer-grade" car (meaning not a formula one vehicle) is the Porsche 911, which can do it in 27m. This is nearly 6 vehicle lengths. Usual safety guidelines are to stay about 3 car lengths behind whoever you're following, so even world's greatest brakes are not gonna save you if the vehicle in front stops in 0m because it hits an immovable pile of already stopped objects itself.

3 car lengths seems way too close to be following at highways speeds. Assuming a car is about 16 ft long, that gives you less than half a second of reaction time at 70 mph. Even at 25 mph, it's still less than 1.5 seconds.

I very much prefer to be 3 SECONDS behind the person in front of me. It's a nice metric that works at basically all speeds above 30.

According to the Utah government's Drivers Handbook[0] (printed page 27, or PDF page 36), they recommend a 2 second distance on clear dry roads:

following distance Watch when the rear of the vehi- cle ahead passes a sign, pole, or any other fixed point. Count the seconds it takes you to reach the same point (one-thousand-one, one-thousand-two.) You are following too close if you pass that point before counting two seconds. Slow down and check your new following interval. Repeat until you are following no closer than two seconds. Always increase your following distance on slick roads, when following large vehicles, motorcycles, or vehicles pulling a trailer, at night, in fog, in bad weather and when following vehicles that stop at railroad crossings (transit buses, school buses or vehicles carrying dangerous mate- rial.)

[0] https://dld.utah.gov/wp-content/uploads/sites/17/2022/01/Dri...

Please point me to the safety guidelines that say to keep 3 car lengths behind on the highway!

The most common guideline I've heard is the two-second (or sometimes, three-second) rule; that's roughly 54m at 60mph, assuming two seconds.

> Usual safety guidelines are to stay about 3 car lengths behind whoever you're following

Uh, no. Usual safety guidelines are to stay a speed-dependent distance behind whomever you're following. The one I've heard most often quoted is one car length per ten miles per hour, so at 70mph you should be a minimum of seven car lengths behind.

Three lengths is comically short for those kinds of speeds.

> Usual safety guidelines are to stay about 3 car lengths behind whoever you're following

No, safety guidelines are to follow 3 SECONDS behind the car in front, which is about 100m at 70mph.

That is why you should always leave enough space in front of you so that you can react and safely come to a stop if the car in front were to suddenly hit a pileup.

Right. Other people will see the gap and will insert themselves in it. What then?

I try to keep a healthy distance, but I've never been able to reserve enough distance to account the car in front of me hitting a brick wall.

Then I just maintain the gap to account for them. I have never been unable to do this. It does mean sometimes I drive 1-2 kph slower than the average speed.

The braking distance at 70mph is a huge 75m, which is about 9 London buses. Add your reaction time, and do you aee why distances of over 100m between cars are slightly unrealistic?

In the event of a pileup, it doesn’t really matter how much distance you’ve left. If you end up hitting the car in front of you, you get cited for failure to maintain distance. Because, if you had left enough distance, you wouldn’t have hit the car in front of you. It doesn’t matter if you left 50, 75, or 100m. If you hit the car in front, you didn’t leave enough space. And the risk of someone else swerving into that gap doesn’t mean you’re not at fault, it just means you’re both wrong now.

> In the event of a pileup, it doesn’t really matter how much distance you’ve left.

For legal liability, that might be true. In reality, if you've left yourself a safe amount of distance, you have more opportunity to react to events in front of you in such a way that you minimize damage and loss of life (thus mattering).

If you’ve left enough room, you’re not part of the pile up. Kind of by definition…

Even if you still crash, the extra second of braking time can take off ~10-15 mph [0], which at 60 mph V(t=0) is ~40% of the energy that would otherwise dissipate into your car and the cars you hit.

[0] https://copradar.com/chapts/references/acceleration.html

> And the risk of someone else swerving into that gap doesn’t mean you’re not at fault, it just means you’re both wrong now.

Sounds a lot like 'climate change is your fault', because there is nothong I can personally do, you are just shifting the blame

No, at 70mph (31m/s) you travel 100 metres in 3.2 seconds. I was always taught 3 seconds on the highway is a safe following distance, and 4 seconds in adverse weather conditions like rain.

It's not at all unrealistic - it's safe.

Where do you live/drive?

BC: https://www.icbc.com/road-safety/crashes-happen/speed/Pages/...

> Allow at least two seconds' following distance behind other vehicles in good weather and road conditions (three seconds on a highway).

> Slow down for poor weather conditions or uneven roads and increase your following distance to at least four seconds. Remember that the distance required to stop increases in wet or slippery conditions.