Study of Integrated Control Strategy of Urban Expressway Traffic Systems and Correlated Surface Street

An integrated control strategy of urban expressway and traffic signal control is proposed in this article. ALINEA control approach is adopted for ramp study so that expressway is ensured to be unblocked. When overfull queue does not exist at the on-ramp or correlative section, the object is to minimize the vehicle average delay on ramp and intersections based on the precondition that expressway is unblocked. When overfull queue exist only at the on-ramp, green truncation strategy or red extension strategy is adopted. When overfull queue is only existed at correlated section of signal intersection, green extension strategy or red truncation is adopted. When overfull queue exist both at on-ramp and correlated section of signal intersection, road guidance and VMS control are activated. Cell transmission model is adopted for signal control surface street so that the cycle and green time of intersection can be optimized dynamically to maximum the whole benefit of expressway and surface street. The model and the control strategy have been illustrated via a simple case study, which shows that integrated control strategy proposed in this paper can keep overfull queue from the on-ramp and correlated intersection while vehicle average delay of correlated intersection is still acceptable.