Jerks actually reduce the risk of traffic jams | Hacker News Reader

Jerks actually reduce the risk of traffic jams

physicsbuzz.physicscentral.com

28 pointstimf22 comments

That conclusion is a weakly implied by the research (at least the way it was explained), which was based on "a computer model of how a crowd of people move across a confined space".

They did not clarify how it applied to car-traffic. For instance, people react very differently to minor collisions while walking versus driving. I'm just guessing here, but I would think the simulation does not account for complicated behavioral factors (e.g. some people, when cut off, may overrreact when hitting their brakes, thus causing more traffic behind them).

The best way to avoid traffic jams is to adjust your speed according to the person in front of you by accelerating smoothly and decelerating without braking. Sudden stops cause traffic waves.

http://trafficwaves.org/

It's best just to leave a big gap between yourself and the car in front of you and drive at a slower speed. Your average speed will probably end up being the same anyway as if you had continually accelerated and braked abruptly, but it would be less frustrating.

The biggest gap in front is left by stopping altogether. This is also the safest posture a driver can take but it accomplishes nothing.

Yes, leave room in front but also have some consideration for the person behind you. If I can't (or am not willing to) pass, I try to leave as much room behind me while staying a safe distance from the vehicle in front of me as possible.

In traffic, making space in front of you usually creates safer distances between those behind you as well.

You slow down a bit so the one who drives behind you gradually drives closer until he notices that you slowed down. Then he realizes he must slow down as well, making space between you and him, and the safe distance propagates further backwards.

Would that this theory worked so well in real life where different drivers have differing motives for being on the road. If everyone's priority was to get off of the road as fast as legally possible, you could assume a uniform speed just below the limit. The only problem left to solve would be creating space between the vehicles and the approach you've mentioned would likely work well.

However, the road is full of people who are more concerned about watching the scenery pass, carrying on a phone conversation or looking for landmarks in unfamiliar territory. This is perfectly fine until traffic starts backing up behind them. As cars are added or lanes reduced away, a jam becomes increasingly imminent. And jams are just the extreme example. Patient motorists driving slowly behind distracted ones still have their goals deferred.

What I'm saying is, haste is relative. Slow down if you want to--it's a free country. Just have some consideration for the people behind you.

This also greatly improves your and your fellow drivers' gas mileage.

nyt had a great feature analyzing the effect of the "jersey merge" last year:

http://www.nytimes.com/2008/08/03/magazine/03traffic-t.html

That's a really good article.

I like it, too. The "early 1900s Dane" not mentioned by name is Erlang, btw.

Definitely the most amusing journalism piece I've read lately.

It also didn't smack of that whole "I don't know what I'm talking about" thing that plagues modern journalism.

"However, there is one rule you shouldn't break... the 'three-second rule' for following distances; after the car ahead of you passes a point on the road, count to three."

Three seconds? I've heard of the two-second rule, which has an entry on Wikipedia:

http://en.wikipedia.org/wiki/Two-second_rule

When did the extra second get added?

Two seconds is what I learned years ago. (My guess is that I am older than most participants on HN.) In actual practice, if I am more than two seconds behind the car in front of me, some car will pull in from another lane to fill the gap. I'm lucky to keep my desired two seconds most of the time.

I just check how many dashes on the highway... the distance from the beginning of one "dash" to the beginning of another is 40 feet... So at 70 mph you need at least 5 dashes.

The two-second rule is definitely the bare minimum... At 70mph that's 210 ft/s, and depending on whether the car in front of you can stop faster, that might not be enough distance.

Very cool - I did not know this measurement, though it seems painfully obvious now that you've pointed it out. I will start using the lane dashes; thanks.

I always wondered if you need less than two seconds if you're behind a vehicle that can't stop very fast (e.g., a large truck). Your superior stopping rate could make up for the decreased reaction time.

This can fail horribly. Consider that the truck can decelerate faster than its solo braking ability by hitting a wall or another car. Chain reaction pile-ups aren't only about reaction time.

So, you can count on not being forced to collide by the driver acting alone, but it takes some extra margin to reduce the threat of rear-ending by a poor braker following you, and to account for obstacle-assisted braking by the driver in front.

wow I never thought about that. Thanks!

When I was in Driver's Ed, I got told to use 4 or more seconds.

Then you must be older than me, as when I learned to drive in 84 it was 3 seconds. I think is below one now.

I sometimes do a 3 second gap just to see how fast people will fill it up.. which is instantly.

'Platoons' are potential pile-ups++. My wife used seek these out. She said she thought of them as being like a group 'hug'. It's much safer to spread out a bit.

The instantaneous risk incurred by speeding away from the group for a bit is usually far lower than the sum of sustained risk it averts.

Slowing down only helps until there's someone behind you. The real issue is traffic density. If it's 2AM and you're the only one on the road, you couldn't cause a wave if you tried. Traffic density can be reduced by increasing the speed of traffic and or the number of lanes as well as by reducing the number of vehicles.

Waves are an interesting phenomena to keep in mind but if everyone were to slow down, there'd be problems at the on-ramps (in addition to the cost in time just from being slow). You need the guys at the front to speed up until they can move right/exit to a less-traveled road.

At least until they wreck and hold up traffic for hours.

Just to clarify for those who didn't RTFA: 40% of jerks is the best. More than that is counter-productive.

100% of jerks is worse than 100% of non-jerks.

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