Is parking permit management effective for multi-modal transportation systems with carpooling and high-occupancy vehicle lane users?

This paper studies the morning commute problem in a linear transportation corridor that is connected by a general purpose (GP) lane, a high-occupancy vehicle (HOV) lane, and a transit line. Commuters can choose solo-driving or carpooling, or take transit to fulfill their journeys between home and the workplace in the morning. In previous studies, carpoolers are often to be assumed to use the HOV lane only for facilitating model formulations and derivations. In reality, carpooling users can and will opt for using the GP lane when they perceive a congested HOV lane. Although a few studies have relaxed this assumption, they intentionally separated solo-driven vehicle and carpooling vehicle flows on GP lanes, and unrealistically considered fixed carpooling-related extra costs and money-cost savings, because both fuel and inconvenience costs are travel-time/distance-dependent. Moreover, very limited attention has been paid to analyze the impact of parking availability on carpooling and HOV-lane choice behavior in the literature. To address these issues, we firstly relax the assumption and formulate a multimodal user equilibrium (UE) model for the commute problem with GP lane, HOV lane, and sufficient parking spot supply to characterize users’ behaviors of carpooling, departure time, and mode choices. Our analysis is then extended to address the case where the impact of insufficient parking supply on the departure time choice of solo drivers and carpoolers is incorporated. On top of this, we propose three parking permit management schemes for traffic management, namely, undifferentiated, tradable undifferentiated and system-optimum parking permit schemes. A couple of numerical analyses are conducted to evaluate and compare the effectiveness of the three parking permit schemes. Numerical results reveal several managerial insights. First, increasing the number of carpooling participants per vehicle enhances the comparative advantage of carpooling. Second, restricting carpoolers to use only the HOV lane yields a bias in measuring the system cost, especially for the case with moderately insufficient parking provision. Third, if carpoolers are restricted to the HOV lane, the effectiveness of the undifferentiated parking permit allocation scheme is overestimated and if carpoolers are allowed to use the GP lane, it is only effective for the case with severe shortage of parking provision at the destination. Fourth, the tradable undifferentiated parking permit scheme consistently improves system performance when parking provision is inadequate and it plays the same role as the system-optimum parking permit scheme in enhancing travel efficiency when parking provision is severely inadequate.