Assessment of Integrated Arterial and Freeway Operations Control: Case Study for I-75 and Opdyke Road Corridor, California

Integrated freeway-arterial control implemented using systems approach is an effective traffic management tool during both recurrent and non-recurrent incidents. Its success hinges on several interrelated factors: Incident identification, including precise spatiotemporal characterization; estimation of associated capacity repercussions; activities in nearby special generators; and determination of thresholds necessary to trigger predetermined operational changes. This case study involved a stretch of an interstate route with a parallel major arterial and several ramps. Traffic flow and roadway capacity fundamentals were used to quantify, and then convert, specific incident scenarios into actionable information. Different incident severities with varying levels of freeway capacity loss and duration were simulated. Integrated control during off-peak time but during events in nearby major special generators was also evaluated. The integrated control schemes involved different freeway diversion strategies and concurrent signal timing changes on the parallel arterial. Effectiveness of integrated control was measured through differences in travel time. A base case condition (no incident and no diversion) was simulated as a benchmark. Simulation results show that integrated control of the corridor traffic is beneficial. The level of gains varies with the severity of the capacity loss on the interstate section, the available reserve capacity on the parallel arterial, and the selected signals timing strategy. The benefits of the integrated control schemes become less significant as the level of congestion increases on the arterial and its crossing roads.