Experimental Findings about Wide Moving Jams: Case Study in Beijing

Abstract

Wide moving jams (WMJ) have been reported for over a decade in the three-phase theory. However, existing studies about wide moving jams have mostly been based on simulation data or limited empirical data. In addition, wide moving jams have been studied by only a few researchers, and identification of wide moving jams is still an important issue. Based on a large amount of real-world floating car data (FCD) in Beijing, this paper discusses the identification of wide moving jams and evaluates their impact on traffic flows. The identification of wide moving jams was studied based on the spatiotemporal characteristics of link-based travel speeds. It was found that wide moving jams were widely recognized. Next, the characteristics of traffic speed and the propagation speed of wide moving jams were studied. The average vehicle speed inside wide moving jams was 8.0 km/h, and the average propagation speed of wide moving jams was −8.7 km/h. Finally, the influence of wide moving jams on traffic flows was quantitatively studied for the 3rd Ring Road in Beijing. This paper contributes to the identification of wide moving jams based on link-based FCD with specific space-time granularity instead of the trajectory-based FCD that has been used in previous studies. Wide moving jams are common occurrences, but they are difficult to identify due to the inappropriate space-time granularity of the data. Wide moving jams show different characteristics when the space-time granularity of the data is different. The engineering applications of the findings in this paper include two aspects: (1) traffic control to avoid traffic breakdown induced by wide moving jams, and (2) predictive routing for travelers according the propagation speed of wide moving jams. The influence of wide moving jams on the probability of traffic breakdown and capacity in wide moving jams are further studied.