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Comment by yamtaddle | Hacker News Reader

You basically can't, realistically, do that in dense city highway driving, which looks like what this is. Like, we still say the driver who hits the back is "at fault" in these kinds of pile-ups but it's entirely a "there, but for the grace of God, go I" situation. They were just unlucky. 99% of drivers on that road drive the same way they were, and the ones who don't are probably driving in a way that makes things less safe.

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> You basically can't, realistically, do that in dense city highway driving, which looks like what this is.

Yeah you can.

The maximum carrying capacity of a single lane of highway traffic is around 1900 cars per hour (that is from real-world measurements of what human drivers can actually achieve). At 70 mph that is 194 feet per vehicle. Even assuming something like a 20 foot long F250 or something that leaves 174 feet of spacing between vehicles. Which is nearly 9 vehicle lengths and nearly 2 seconds of room. Up until you hit that point you're not impeding any traffic flow by adding more space. Almost nobody in this video is leaving that much room.

What causes traffic congestion and causes that 1900 vehicles per hour number to be that small is the people who are tailgating and when someone brakes everyone behind them has insufficient following distance and has to brake harder and harder until you've got vehicles nearly stopped on the freeway and have formed a traffic compression wave (if you haven't just created an accident and snarled traffic even worse).

No, you generally shouldn't drive that anomalously. A driver will pass you and insert themselves in front of you. You will fall back to create distance. Another driver will pass you and insert themselves in front of you. You create constant aggravation and churn around your car.

Source: I spent several months last year helping someone learn to drive in the Bay Area, and they insisted on leaving the recommended gap between cars as they prepared for their driving test.

That doesn't matter. And if you're not in the left lane usually people merging in front of you are heading for the "fast lane" (which is typically even more congested and slower) or heading for the exit lane. Just let them go on their way, into and just as rapidly out of your life.

And if you don't let yourself feel "aggravation and churn" then people will just merge into and later leave your lane and it just becomes normal driving without any ego involvements.

Source: the past 30 years of driving in Seattle traffic that I've done where I've stopped being a tailgating idiot and opened up more space and stopped caring about people "cutting me off".

Churn is not a feeling of your ego. Churn is the physical movement of cars on the road that creates numerous additional opportunities for collision.

100 people merging into 170 feet of space in front of you[*] is dramatically safer than 1 person trying to squeeze their way into the 20-30 feet of space you're leaving in front of you when you're tailgating.

[*] not all at the same time...

if they do, so what? even if 10 people cut in front of you, with a 30 minute drive, how much time are you really losing? 50 seconds?

In several countries in Europe they occasionally paint markings on the road (chevrons or dots or similar) with a sign like "Keep apart 2 chevrons". Some places have electronic speed limit signs to reduce the maximum speed in heavy traffic, which reduces risk and improves flow.

https://www.alamy.com/stock-photo-keep-apart-2-chevrons-moto...

(Obviously we can't tell the speed of the cars in the photo, but if it's the standard speed many drivers are still ignoring it.)

That's a UK motorway, so assuming the national speed limit applies they'll be travelling at around 70 mp/h.

There is very heavy traffic on both sides, so it wouldn't be unusual for the actual speed to be 50mph, 40mph or even less. The second nearest car is braking, and there's a "Queues Likely" sign a little further -- I found the place:

https://www.google.com/maps/@53.3015568,-2.722796,3a,75y,235...

StreetView gives a much better impression of the chevrons; the Alamy photo has an unusual choice of lens. The "M56 B 45.0" [km] milepost is way ahead of the chevron sign.

Sounds like a case for gap cameras similar to speed cameras.

Oh the money that could earn.

They'd have a revolt on their hands in short order, around here, and I suspect in most places. You can't handle enough traffic on the parts of our highways that go through the city, while maintaining the kinds of gaps that would be necessary to avoid these sorts of wrecks (well, the later pile-ons, anyway). Commute times would shoot up and areas that don't usually experience congestion would become intolerable around rush hour, if people really started leaving that much space, consistently.

Which is, perhaps, one of many arguments against having so many people on the roads to begin with, but that's what we have.

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