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Old 04-09-2013, 05:21 PM
Elroch Elroch is offline
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Join Date: Mar 2013
Posts: 143
Default Re: question 2

This is a fascinating topic. I have no doubt that the answer is correct, in that this application is one suitable for machine learning, but the details are far from obvious.

Firstly, the time the lights are on for is not really a suitable target (unless the aim is merely to emulate conventionally programmed systems). This is something that is completely under the control of the system, not something to be predicted.

My first thought is to seek something to optimise. A bit of pondering leads me to average time spent waiting by vehicles. With different traffic light schedules, this will vary and is a reasonable target for optimisation. [It might be improved by weighting long waits more heavily to avoid being excessively unfair to vehicles from minor roads]

But we also need to identify the set of inputs. Far from trivial, but the basic idea is to concisely represent every possible control protocol that might be considered usable. In addition, all the observed information that is available to the system must be included: this could be nothing at all, or it could include various information about vehicles reaching or leaving the junction.

As for input data there are three possibilities. The first is to use data from existing systems of any type at junctions that are similar to one of interest. The second is to use data from the junction itself and use some sort of reinforcement learning. The third is to use simulations of junctions, using realistic vehicle data, and predict the performance of a selection of control protocols. Machine learning could then be used to extend this knowledge to billions of protocols by generalisation. With a bit of luck.

I am now reminded that 23 years ago I had an interview at the Transport and Roads Research Laboratory where they asked me for my thoughts on how traffic light control systems could be designed. Given the naivety of my answer, I'm not sure how I got offered a post: in hindsight perhaps I should have accepted it rather than the one I did take.
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