Study On Capacity Of Reconstruction And Extension Of Expressway Work Zone

In recent years,with the vehicle ownership increasing,the original expressway has been unable to meet the growing traffic demand.Comparing to the newly built expressway,the reconstruction and extension project has benefits of shorter construction period,less investment and less impact on the traffic.In 2002,the reconstruction and extension project of Shenyang Dalian Expressway was launched,followed by other reconstruction and expansion projects across country(e.g.Huning,Guangfo,Huhang Yong,Lianhuo,Jingzhu,Fokai,Jinggang Macao and so forth).The Expressway reconstruction and extension mode has become the major trend in China for highway network improvement.However,work zones in the reconstruction and expansion projects become bottlenecks that have significant impact on traffic operation and safety.Consequently,studies with respect to capacity analysis and traffic design in work zones are important for dealing with these issues.The reconstruction activities in work zone have impact on the traffic flow characteristics and reduce the capacity of corresponding road section as well.In order to figure out the influence toward traffic flow raised by work zone,this paper analyzes the traffic flow characteristic in terms of different lanes and capacity change in each work zone sections(warning section,transition section and activity section).The study is based on the Guangxi Lan-Hai expressway reconstruction and extending project and the hourly traffic flow data was collected constantly since November 2017 to June 2018.Main contributions of this paper includes: 1)identified the bottleneck in the work zone by comparing the traffic flow characteristics within different control sections;2)compared the traffic flow characteristics in each lane of the objective work zones and obtained a functional relationship with respect to traffic volume and speed;3)regarding the feature of work zones,a new definition of work zone capacity was proposed based on the queuing flow rate and 4)values of work zone capacity was obtained along with calibrated parameters through VISSIM simulation.The parameters in the VISSIM are calibrated by using orthogonal experiment method based on the observed traffic flow data.The result identifies the transition section as the bottleneck in the work zone.In addition,the lane change behavior of vehicles has significant impact on traffic operation: the traffic flow will change suddenly as density is greater than 30 veh/kmand the frequency of lane change increases a lot if the density in work zone is greater than 15 veh/km.Plus,the lane changing behavior has more impact on inner lanes comparing to that of on outer lane.By comparing the maximum flow rate before and after traffic shut down for different road cross section,we found: 1)for road section with two lanes on each direction,the maximum flow rate will be reduced by 8.56%after congested if outer lane is closed.2)For road with three lanes on each direction,the maximum flow rate will be reduced by 10.56% after congested if the two outer lanes are closed 3)and the maximum flow rate will be reduced by 9.75% after congested if two inner lanes are kept.Moreover,the traffic simulation shows that the speed limitation and opening length of median fence are positively correlated to the work zone capacity.Lastly,the coefficient of traffic composition with respect to the work zone capacity is calibrated as 0.74 by simulation as well.