from Hacker News

Smarter programming of stoplights could improve efficiency of urban traffic

by meneses on 4/1/15, 1:31 PM with 45 comments

• by WalterBright on 4/1/15, 8:16 PM

  With all the image processing cameras out there, and the cameras already mounted on the traffic lights, it boggles the mind that nobody is making traffic light controllers that optimize traffic based on current conditions and a cost function.

  For example, if 5 cars are coming from one direction, turn the light red for the 1 car on the cross street.

  I'm pretty fed up with the light perversely stopping the 5 cars at the last moment to let one car, that is already stopped, enter the intersection from the cross street.

  I wonder how much gas and congestion can be saved this way.

• by heydenberk on 4/1/15, 9:29 PM

  It's a neat thought, and everyone who's watched a light turn red ahead of them just as they cleared a green has thought it before, but there is a serious downside. Urban stoplights should be optimized for the safety of non-motorists (pedestrians and cyclists) above all else. Giving cars more uninterrupted travel leads to higher speeds and more collisions. I'm happy that where I live there's more attention paid to traffic calming and bicycle infrastructure than motorist travel-time optimization.

• by 3minus1 on 4/1/15, 8:18 PM

  Virginia currently uses smart traffic signals:

  > Traffic-responsive signals vary the timing of the lights according to the amount of traffic. They use sensors to detect the number of vehicles on an approach. The time the light stays green adjusts to let as many drivers as possible through before the signal changes to respond to traffic coming from another direction.

  Back when I lived in NoVa, the lights near me had this and it was awesome

• by jakejake on 4/1/15, 7:55 PM

  I sometimes get the feeling that traffic signals in my home town (Chicago) are designed to maximize ticket and speed camera revenue, rather than improve the flow.

• by j_s on 4/1/15, 10:03 PM

  Startup opportunity: micro payments to change the light green in your direction ASAP. Voice-activated bidding with a floating fee that everyone sitting at the light can contribute towards.

• by ChuckMcM on 4/1/15, 10:27 PM

  There is an interesting side effect here. Autonomous learning.

  Basically when the stoplights in my city switched to a 'three program' light (they have 'normal workday', 'normal non-work day' and 'commute' patterns available it means that people who drive "on autopilot" start having the wrong thing anticipated when they are sitting at the light, (for example expecting a left turn signal to go green before oncoming traffic gets the green, or expecting turn signals to activate before through traffic) and that leads to some interest effects. Most notably people "jumping" into traffic when their anticipation is incorrect.

  The other thing that this does with non-native/less well trained drivers, is put them in lose-lose situations. I got out and talked to a guy who was sitting in a non-left lane (it was one lane over), waiting for the left turn light to activate. I explained to him (he barely spoke english) that from the lane he was sitting, the left turn light would NEVER activate and by sitting there while the light in front of him was green he was at risk of being hit by a car. He had no clue. It was very sad.

• by joe_the_user on 4/1/15, 8:29 PM

  This seems like a nice idea but I actually think it would be terrible. The big discovery recent-ish is "Traffic Expands to Fill Available Road Space" [1]. A situation where traffic lights become smarter to keep traffic balanced between main streets and side streets and between different intersections of the city would just mean result in every single intersection of a given city being in grid-lock simultaneously rather than just some of them.

  Already, I've notice that rush-hour lights seem to tuned to take longer than mid-day light - assume that's because any light-change is going to be inefficient (logically enough). But since rush is fated to total congestion anyway, the result just congestion plus tortuously long lights.

  [1] http://www.culturechange.org/issue8/traffic%20expands.htm

• by shijie on 4/1/15, 9:06 PM

  Or, we could use roundabouts[0]

  [0]: http://www.wsdot.wa.gov/Safety/roundabouts/benefits.htm

• by nerdy on 4/1/15, 11:22 PM

  Highway commutes will be significantly streamlined when merges are done in a perfectly interlaced fashion with autonomous drivers. Anyone who has tried to get on the highway in the US during rush hour probably knows exactly what I am talking about.

  Imagine driving on roads where all the vehicles followed the rules and you didn't have to pay attention and the road system worked with the vehicles to improve efficiency.

• by arasmussen on 4/1/15, 8:18 PM

  I would love to see this implemented in SF. Every day I drive I see one light turn green just as the next one turns red. You really can't do much worse.

• by allochthon on 4/1/15, 11:33 PM

  Note that some cities optimize for driver inconvenience, to discourage driving through the city center.

• by vinchuco on 4/2/15, 2:47 AM

  If you want to minimize traffic, instead maximize the number of people transported per vehicle.