Impact of curbside bus stop locations on mixed traffic dynamics: a bus route perspective

Intermittent lane blockage at curb-side bus stops, characterized by aggressive lane changes, undue traffic delay and drop of road capacity, creates the major bottleneck in mixed urban traffic. This paper develops an extended link-node structured two-lane cell transmission model (CTM) that is capable of dynamically capturing the effect of lane blockage at bus stops and comprehensively modelling mandatory and discretionary lane changing (MLC & DLC) manoeuvers along a bus route under various traffic demand levels. Such modelling features, with proper calibration, have been validated to outperform the traditional CTM in terms of replicating the impact of curbside bus stops on mixed traffic dynamics. Application of the proposed model at a route level indicates existence of the optimal distribution of bus stop locations that minimizes the total traffic delay regardless of link lengths and stop densities on the route. Microscopic traffic flow characteristics such as time-varying DLC, MLC and cell densities along the bus route further demonstrate the capability of the proposed route-level model to capture the traffic phenomena (e.g. turning traffic and spill-over exacerbated by stops very close to upstream intersections) that are underrated in traditional single link or intersection based studies. The proposed model, embedded with a mathematical optimization framework, may provide insights in better planning, design, and relocation of curbside bus stops along urban streets to mitigate traffic congestion and to improve bus service.