Operational performance optimization of signalized intersections is one of the most important tasks for traffic engineers and researchers. To compensate for the limitations of practical implementation, simulation software packages have been widely used to evaluate different optimization strategies and thus to improve the efficiency of the intersections as well as the entire network. However, for the existing optimization studies on signalized intersections, the relationships among various optimization measures and the combination of strategies have not been fully investigated. In this paper, uniform design experimentation was introduced to combine different optimization measures into strategies and achieve the minimum time cost in model construction. VISSIM software package was then calibrated and used to evaluate various optimization strategies and identify the one with the best measurement of performance, namely, control delay at the signalized intersection. By taking a representative congested intersection in Shanghai as a case study, the optimal strategy was identified to reduce the overall control delay by 27.3%, which further verified the modeling capability of the proposed method.

This paper provides a safety assessment tool (SAT) for long-span bridges in China. The authors selected the Sutong Yangtze River Bridge, one of the largest long-span bridges in China, for a case study. Currently, safety assessment of long-span bridges in China is primarily based on human judgment. No effective method exists for estimating the traffic crash risk of long-span bridges under various conditions; this situation creates difficulty in providing effective safety control strategy and developing counter-measures. In this study, the Traffic Software Integrated System was used to simulate the traffic on the Sutong Bridge. A safety assessment model (SAM) was developed from four contributing factors: traffic volume, free-flow speed, percentage of heavy vehicles, and weather conditions. SAM was used as the basis for developing an SAT that could aid policy makers and traffic professionals in better understanding of traffic safety of the Sutong Bridge: (a) a risk map was created to indicate different safety levels of the bridge under various conditions and (b) a user interface was designed to allow users to identify the safety level of the bridge quickly and easily.