Bottleneck Geometric And Control Strategies For Reducing Congestion On Urban Expressway

In recent years,congestion has become the main traffic problem on most urban expressways.Furthermore,the bottleneck is considered to be the main cause of congestion.The bottleneck phenomena have caused a lot of negative impacts on the transportation system and even on economic development,as well as an increase in travel time and travel delays for individuals and society.The improvement of traffic and elimination of bottleneck can be carried out from the aspects of road geometric design and traffic flow control.As a consequence,how to put forward strategies to eliminate the impact of bottlenecks and alleviate congestion has attracted the attention of scholars all over the world in the past 20 years.The study objectives were to improve and mitigate the traffic flow of bottleneck areas by reducing travel time and delay by using new strategies.Also,to improve the expressway safety by making the estimated incidents in these areas less than before.Four geometric and control strategies were proposed to reach the objectives of this study.Bottleneck sites were identified through continuous monitoring of real street maps through Baidu Map and fieldwork.The data were collected from some sites by drone.Thereafter,the identified sites were simulated using the new strategies by VISSIM software.The SSAM software was used to determine the safety impacts of these sites after applying the new strategies on the current suffering sites.Travel time after improvement was reduced by 44%,43%,29%,38% and 46% for Jiangdong Middle Rd,Ji Village Rd,Yingtian Rd,Longjing Road and East Ring Road,respectively.Moreover,the crossing,rear-end,lane-change and total conflicts in these five segments were reduced by 100%,58%,42%,and 66% respectively.Finally,the results concluded that segments after applying the improvements have reduced both travel time and delay.Furthermore,conflicts were reduced in every segment.