
Shockwave traffic jams recreated for first time
About this video
A one-minute New Scientist clip showing a Japanese experiment in which drivers on a circular track produce a spontaneous traffic jam that travels backward. It illustrates phantom traffic jams without any obstacle.
Why it appears in the archive
It is the go-to demonstration HN links whenever traffic shockwaves, phantom jams or cascading failures come up.
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From the Hacker News discussion
This article accounts for some of what causes traffic jams, but have a look at this video. It shows a study done where people tried to drive on a circular track at a constant speed. Things start out okay, but it quickly devolves into the back propagating wave. [VIDEO]
Read original comment ↗Some Japanese scientists did a study to show how traffic jams can appear of of nowhere. They told 22 drivers to drive in a circular path at 30 km/h. A traffic jam appeared, and moved backward. The video is here: [VIDEO]
Read original comment ↗TBH, if you are going to have smart intersections controlling autonomous cars, you might as well try to move to roundabouts as much as possible. Roundabouts provide continuous flow and probably represent a much more solvable problem since it involves attenuating the speed of approaching vehicles and vehicles currently circling. I imagine throwing stopping into the mix complicates things significantly I imagine that computers could completely prevent shockwave traffic jams. [VIDEO]
Read original comment ↗NASDAQ telling the market "you have until noon Monday to prove your losses" most definitely did cause people to dump stock in the first two days of trading. Confusion over whether trades were happening because NASDAQ wasn't confirming orders probably caused investors to be skittish, which could easily have had cascading negative effects. It's hard to say if FB's stock was overpriced. The GM thing couldn't have helped. But to say NASDAQ had nothing to do with it is silly. I look at FB's IPO and think of this[1]. Little (and not so little) permutations causing shockwaves through the system. 1. [VIDEO]
Read original comment ↗Did you read the article? There is no single car that causes a jam. In fact according to previous research [LINK] (see "Conclusions" at the bottom), even if all cars follow the same rules a jam can still occur. They can also occur in very simple situations like in this video [VIDEO]
Read original comment ↗Self-driving cars are the necessary but not sufficient condition to solve traffic problems. Start with that and remove 1-person-1-car model [0], add ride-sharing software, ban human drivers [1] and done, no more traffic problems. As for your example - this jam is a direct result of very high latency of human reaction. It causes stop-and-go in jams [2]. [0] Or it will rot and occupy parking space for 97% of time. [1] This will likely to average speed and reduce time spent waiting for lights. [2] [VIDEO]
Read original comment ↗I think if it's annoying, you're not driving in traffic the right way. Sure, it's annoying for aggressive stop-and-go driving, but if you maintain a consistent speed with the traffic in front of you (see traffic shockwaves [0]), a manual transmission is better than an automatic. [0] [VIDEO]
Read original comment ↗This model is overlooking some aspects of traffic flow. The most important one is that flow does not increase and decrease smoothly. As density increases there starts to be shock waves that bounce longitundinally[0]. It would also makes sense to also distribute some autonomous vehicles along the train to minimize these shock waves. A much simplier solution is to autonomously centre between the vehicle in front and rear[1]. Doing so smoothly is simple local logic which may improve flow rates dramatically but I don't know if it's been implemented anywhere. [0] [VIDEO] [1] [LINK]
Read original comment ↗