New developments from the world of urban traffic science: Apparently, what we want is a decentralized, “self-organizing” system, in which individual traffic lights don’t run according to a rigid program, but make local decisions based on global information.
From Popular Science:
[The researchers] started by modeling traffic as if it were a fluid, comparing intersections to a network of pipes. Then they gave each traffic signal a sensor that provides information about traffic at a given moment. Computer chips in the lights calculate the expected flow of vehicles, and determine how long the lights should stay green.
But this “jungle principle” of every light for itself does not result in harmony, the researchers said. If each traffic light responds to its immediate demands, then all the lights will just react to the traffic coming from nearby intersections, which defeats the purpose of a smart network.
The solution is a decentralized approach that lets the traffic lights work together by figuring out how changes at each individual intersection would affect the entire system. Instead of being stymied by natural fluctuations in traffic, the system takes advantage of them, using random gaps to help improve traffic flow. Traffic lights could request green time only when there is a definite demand for them, the researchers write. This acyclic approach could eliminate the particularly annoying problem of sitting at a red light while there’s no traffic.
Normally, traffic lights run on coordinated, rigid cycles that are programmed according to normal traffic patterns. In this system, by contrast, each traffic light has much more flexibility to turn itself green or red depending on both its own local traffic conditions and the effect its state will have on surrounding intersections.
Where the status quo is rigid and centrally programmed, this system is decentralized and flexible. The researchers estimate that an effective decentralized system like this might reduce delay times by somewhere in the 10 to 30 percent range.
I’m not qualified to provide a useful technical assessment of the quality of this research. You can download the original paper here. Also, it’s important to remember that reductions in traffic may just offset themselves with increases in driving. The net effect of implementing a program like this might just be a higher carrying capacity for our roads rather than traffic-free driving.
That said, it’s interesting that figuring out how to best program traffic lights, which may seem like a very 20th-century challenge, is actually still at the boundaries of our understanding.
Photo (cc) by Flickr user masochismtango
