Priority for buses at traffic signals

Various methods of giving priority to buses at traffic signals are outlined in three groups, the first requiring only appropriate calculation of signal timings, the second requiring traffic regulations, and the third requiring detection of approaching buses by the signal control apparatus. Although methods in the second and third groups do not explicitly require special calculation of timings, they do have implications for timings and their calculation. For the second group, these implications are simple enough to be described briefly. For the third group, the implications lead to quite extensive theoretical analysis. Because the general theory is rather intricate to describe, the analysis is presented for an example which illustrates the principles fully without giving rise to too many complications of notation. This analysis also provides an example of the application of probability theory to a traffic situation from first principles. Some illustrative results are given (a).