Bus Priority of SCOOT Evaluated in a VISSIM Simulation Environment

Transit usage is based on reliable and timely service. Priority is one method for maintaining reduced transit travel times and a reliable schedule, which make transit more attractive. However, with most buses operating within the same traffic lanes as other vehicle traffic, priority policy affects the surrounding traffic. Consequently, priority is often limited to minimal green time extensions or recall, often only when the bus is behind schedule. The Split Cycle Offset Optimization Technique, SCOOT, provides opportunities for bus priority options while also reducing delays for all traffic. A connection between an actual SCOOT system and the simulation VISSIM has been developed to evaluate bus priority performance. A Salt Lake City, nine-intersection modeled corridor, evaluates SCOOT’s performance, both with and without bus priority. The SCOOT analysis is compared to an actuated-coordinated optimal signal timing developed in SYNCHRO. The modeling includes the existing 7-routes on the corridor. A single route with a range of bus headways is also modeled to evaluate the impacts priority with increasing bus frequency. The results indicate that SCOOT with bus priority, compared to the actuated-coordinated timing, reduces non-bus vehicle delays by 16% or 4.4 seconds per person per intersection and bus delays by 27% or 9.2 seconds for the 7-route system. Without bus priority, SCOOT reduced non-bus person-delay by 21% or 5.9 seconds per person and bus person-delay by 5% or 1.8 seconds per person. SCOOT’s bus priority can reduce transit delay with a minimal impact to other traffic.