Design of a Dual-Modal Signal Progression Model for Urban Arterials Accommodating Heavy Transit and Passenger Car Flows

Abstract

Despite extensive studies aiming at contending with congestion on urban arterials, an effective model to produce optimal signal progression for an arterial experiencing heavy bus and passenger car flows remains unavailable. In response to such needs, this study presents a bandwidth maximization model that can offer concurrent progression to both modes or to a selected mode(s) in a selected direction(s), based on traffic volume, bus ratio, and geometric conditions. To capture the operational features of both modes, the proposed model has effectively taken into account all critical issues that may result in mutual impedance between them, which include the potential blockage by passenger car queues of roadside bus stops, the excessive start-up delays caused by transit vehicles queueing at the intersection stop line, and the reduced travel lanes for progressing flows caused by buses dwelling at roadside stations with limited storage capacity. In addition, by weighting the bandwidths with the passenger volumes by mode and by direction, the proposed model is capable of offering progression only to the mode(s) and the direction(s) for which it is justified from the perspective of maximizing the benefits to all arterial users. The numerical analysis results have confirmed the effectiveness of the proposed model in producing concurrent progression bands for both modes under various realistic constraints and volume levels. Further evaluation with extensive simulation experiments has also demonstrated that the benefits offered by the proposed model will not be at the cost of other measures of effectiveness.