Analytical formulation and empirical evaluation of pre-signals for bus priority

One of the major causes of bus delays in urban environments are signalized intersections. A commonly used solution to give priority to buses at signalized intersections is to dedicate a lane for bus-use only. However this strategy can waste valuable green time at signals and impose additional delays to cars, especially when bus flows are low. Overall, the total person hours of delays in the system (i.e., buses and cars) can increase due to excessive delays experienced by car users. To this end, an additional signal upstream of the main signal, called a pre-signal, can be used to better utilize the capacity of the main signal while still providing bus priority to reduce the system-wide person hours of delays.