Modeling and Simulation of Rainfall Impacts on Urban Traffic Flow: A Case Study in Beijing

Recently many studies have emphasized the negative influence of inclement weather on microscopic and macroscopic traffic flow characteristics, including road capacity and operating speed. Although many conclusions have been drawn, only a few researches have investigated simulation-oriented rainfall influences on urban traffic systems. Simulation of rainfall scenario requires detailed theoretical study and statistical calibration, from both demand side and supply side, where related study is limited. This paper proposes a systematic study process to realize the simulation of rainfall scenario, based on a case area in Beijing, China. Firstly, rainfall impacts on urban traffic flow from both demand side and supply side are investigated by using traffic detector data and weather data. Then results are utilized to build a rainfall-integrated module in the microscopic simulation software of FLOWSIM. Results show that with rainfall module, FLOWSIM can describe the rainfall impacts on urban traffic systems with higher accuracy than without rainfall consideration. The methodology can be useful as references for similar studies and future applications; and the calibrated rainfall-integrated simulator can facilitate to improve traffic evaluation, operation, and management. Both data analysis and simulation tests conclude that rainfall has negative impact on urban traffic flow.