POLICY BASED TRAFFIC SIGNAL CONTROL

In reality, all traffic signal control is policy based. Some may not recognize the policy or who is setting it, and that is the point of this paper. The policy may be set by the mayor who orders a signal installation or by the traffic engineer who used the MUTCD. This example is rather obvious. Less obvious in the case where the person doing the signal timing selects a particular tool. The professional timing the signal assumes that are being technically accurate because they are using an accepted tool, when in fact they are setting policy. The policy may be to minimize delay or minimize stops or whatever measures of effectiveness the tool uses. Most tools minimize vehicle delay or vehicle stops, and do not recognize that some vehicles should have a higher priority. Now enter the fire chief requesting a pre-emption. A transportation professional responsible for signal timing may assume that fire priority is undesirable because it disrupts whatever measure of effectiveness that is being optimized. The obvious questions are who should be setting the policy and what should it be? The point of this paper is that transportation professional may assume, because they are using the accepted tool, rational, and objectives procedures, that there is in fact only one right answer, the one that they are implementing. The policy based traffic signal control can be better understood using a hierarchy of priorities. Currently the railroad has the highest priority. This priority is based on the law and lot of history. Second priority is emergency vehicles and the third priority is transit. Certainly 40 people in a bus or 100 in an LRT should be given higher priority than a single occupant car.