Impact Analysis of Rainfall on Traffic Flow Characteristics in Beijing

摘要

To improve traffic operations and management under inclement weather, this work quantificationally investigated the influenceof rainfall on the traffic flow characteristics of urban expressways in Beijing. Four basic traffic flow models (Greenshields model,Greenberg model, Underwood model, and Drake function model) were compared to determine the most suitable model for thedetected data, which were collected by microwave detectors in the Beijing 2nd and 4thring expressway under normal or rainfallcondition. Results showed that the Greenshields model was the best-fitted model. Under rainfall conditions, varying degrees ofreductions were observed in the road capacity, free-flow speed, and speed at capacity. The findings also showed that thereductions of road capacity were 7.26%, 10.87%, and 17.09%, and the reductions of free-flow speed were 3.07%, 5.29%, and6.64%under light rain, medium rain, and heavy rain, respectively. The reductions of speed at capacity revealed a similar tendencyas that of the free-flow speed. Simultaneously, a new model that incorporated rainfall intensity is proposed on the basis of theGreenshields model and can achieve good performance. Overall, the results are beneficial for traffic managers in improving theirdecisions and predictions under rainfall weather.