Design and Evaluation of an Adaptive Traffic Signal Control System - A Case Study in Hefei, China

:As a part of developing an adaptive signal control system using VS-PLUS method for optimal network traffic control, a study was carried out along the Huangshan Road in Hefei, China, to evaluate this system. This paper described the study which included field survey about traffic performance; development of trip matrix using an improved Furness method; using the TRANSYT traffic modelling software to find the optimal fixed-time signal plan and VISSIM micro-simulation software to affirm and evaluate the TRANSYT model and to help assess the optimal signal plan; building adaptive frame signal plan and refining and evaluating the plan using VISSIM with VS-PLUS emulator. The results indicated that average delay per vehicle was reduced significantly with consequent improvement in network performance. Adaptive signal control plan was then designed for the VS-PLUS signal control system based on the optimal fixed-time signal plan. Through micro-simulation, it was shown that delay in the adaptive signal control was shortened noticeably than that in the fixed time control. This study has been the very first for this system. Further and more comprehensive studies are expected to follow to fully evaluate and appreciate this system. This study has filled some of the gaps in evaluating the performance of and provided a benchmark for such an adaptive traffic signal control system in a typical urban setting in cities in China. The study has also raised a number of questions in setting the optimal frame plan regarding driver behaviour, safety concerns and tradeoffs between shorter cycles and higher responsiveness to traffic variations.