Integrated signal optimization and non-traditional lane assignment for urban freeway off-ramp congestion mitigation

Exiting flow from urban freeway off-ramps coupled with limited capacity and traffic weaving at the downstream intersections creates major bottlenecks in urban road network. This paper presents an integrated design model for non-traditional lane assignment and signal optimization at the off-ramp, its downstream intersection, and their connecting segment with the objective to mitigate or eliminate traffic weaving and to maximize the section's overall capacity. A mixed-integer non-linear program model is formulated to capture real-world operational constraints regarding the non-traditional lane assignment, special phasing treatment and signal timing. The mathematical model is linearized and solved by the standard branch-and-bound technique. Extensive numerical analysis and case study results validate the effectiveness of the proposed integrated model and demonstrate its promising application at locations where the upstream freeway off-ramp is located at the middle of the road cross section and the space between the stop line and off-ramp is limited.