5. Conclusions

A control algorithm for traffic lights has been developed under the assumption that the actual state of the crossing is known; i.e. there is a device (an observer) which is able to reconstruct the crossing state, given the input events. The aim of the control algorithm is to minimize the overall waiting time or to maximize the throughput. The control of a single crossing or a crossing with combined phases is pretty easy; coupled crossings have additional co-ordination rules.

The state space does not exhibit (explicitly) time, but ordered customers. The algorithm does not reduce the state space, but

• the number of transitions is reduced, and
• the number of states to be searched all over is be reduced, too.

Problems only raised in the paper are subjects of further research:

• design of an observer,
• simulation of a crossing to test the controller and the observer,
• robustness of controllers and observers with respect to unreliable sensor outputs.