Here is a control law that was evovled when using a traffic network with higher traffic volumes than demonstration 1:
See the page "Using Demos" for important information
Try viewing intersections 3 and 4 to see the control law in action. Specifically, around time index 68, see how at intersection 4, it holds the group of cars in the eastbound lane together. It seems to hold the light green just long enough to let that group go through. In fact, the next group behind them, seems to get caught by the red light, because the timing is so precise.
A four intersection network was used when evolving this control law. It consisted of two one-way streets (both are eastbound) and two two-way streets (both north-south). The eastbound streets had a significantly higher volume, each having 700 cars/hour, and the north-south streets had 450 cars/hour.
This control law is again pretty clever. It keeps switching the phase of the signal (keeps changes the traffic light) so that no one lane gets more green time than it needs. It does this by only returning true when the number of cars in the moving lane has fallen below a certain threshold. This threshold is set by CONSTANT_0, which it learned as it evolved.
This creature was found after exploring 4500 different control laws, with a population size of 500 creatures.