The trouble with traffic at intersections

traffic-lights.jpg

These rather beautiful graphs are space-time plots of vehicles approaching, entering and then leaving an intersection controlled by traffic lights.

The plots were calculated using cellular automata to model the behavior of the vehicles.  Here the upper plot shows the pattern of traffic at a traffic lights with a fixed schedule. The lower figures shows what happens when the lights respond to the weight of traffic. The plots have a certain symmetry and many similar characteristics (in fact one seems to be a larger version of the other).

Ebrahim Foulaadvand at the Institute for Studies in Theoretical Physics and Mathematics at Zanjan University in Tehran, Iran, and a pal say that the work needs to be calibrated with data from real traffic lights to determine the braking and acceleration characteristics of real cars.

You can say that again. These plots seem rather improbable given that traffic flow is well known to demonstrate phase changes as the density of vehicles increases. They don’t seem to have toyed with that problem yet.

Looks like Foulaadvand and co have some work to do if they want their model to match the behavior of real road traffic.

Ref: arxiv.org/abs/0809.3591: Simulation of Traffic Flow at a Signalised Intersection

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