SCSC2003 Abstract S441
Sensitivity Analysis of Transit Signal Priority Impacts on Operation of Isolated Signalized Intersections
Sensitivity Analysis of Transit Signal Priority Impacts on Operation of Isolated Signalized Intersections
Submitting Author: Dr. Hesham Rakha
Abstract:
The study conducts a systematic simulation evaluation of transit signal priority impacts on the operations of an isolated signalized intersection. The study demonstrates that in general transit priority provides benefits to transit vehicles that receive priority. These benefits are highly dependent on the time of arrival of the transit vehicle within the cycle length and the phase of the traffic signal that is requesting priority. Second, transit priority has a marginal system-wide impact for low
traffic demands, however as the demand increases the system-wide disbenefits of transit priority increases. Third, the
system-wide impact of transit priority is dependent on the frequency of transit vehicles. Specifically, as the transit vehicle frequency increases larger system-wide disbenefits are observed. Forth, transit priority impacts are sensitive to the demand distribution at a signalized intersection. Specifically, transit vehicle arrivals on heavily congested approaches may result in system-wide benefits if the conflicting approaches are not congested. Alternatively, transit vehicle arrivals on lightly congested approaches may produce significant system-wide disbenefits if the conflicting approaches are heavily congested. Fifth, the system-wide benefits of transit priority are dependent on the phase at which the transit vehicles arrive especially if the cycle length is maintained within the priority logic. Specifically, transit vehicle arrivals during the early phases produce minimum disruptions to the general traffic while transit vehicle arrivals for the latter
phases produce significant system-wide disbenefits. Sixth, the system-wide benefits of transit signal priority are highly dependent on the optimality of the base signal timings. Specifically, if the priority logic enhances the signal timings system-wide benefits can be achieved by virtue of improving the signal timings. Finally, transit vehicle dwell times at near-side bus stops can have significant system-wide impacts on the potential benefits of transit signal priority. Specifically, the system-wide disbenefits increase with an increase in bus dwell times if the bus stop is located within the detection range
of the traffic signal.
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