Capability-Enhanced Microscopic Simulation With Real-Time Traffic Signal Control

An application programming interface (API) is a feature that is available in some traffic simulation programs to enhance their capabilities by allowing users to customize changes in simulation such as driver behaviors, vehicle characteristics, user-defined control strategies, and advanced Intelligent Transportation Systems (ITS) applications. This paper presents an API in AIMSUN, which is a stochastic and microscopic simulation model, to evaluate a novel real-time signal control technique based on the dynamic programming (DP) algorithm. A transportation network of diamond interchanges is first created and calibrated in the AIMSUN environment. The API, which creates a dynamic link between the DP algorithm and AIMSUN, is then developed and deployed in C++. During simulation runtime, real-time traffic measurements, including vehicle counts and speeds, are provided by detectors in the network and fed into the DP algorithm that subsequently makes a decision on a signal control plan. The signal plan is then transferred back to and implemented in the simulated network, which emulates its actual operation. Extensive simulations have shown that the new signal control technique is superior to other common offline signal optimization tools in terms of handling the demand fluctuations. This paper has demonstrated that the API function is a useful tool to assess new ITS applications that are unavailable in simulation programs.