Study On Capacity Of Bus Lane With Intermittent Priority And Its Impacts

So far,the total mileage of Exclusive Bus Lanes(XBL)are over 10 thousand kilometers in China.In recent years,the development of XBL is increasing due to continued deployment in different cities.Besides,the motor vehicle ownership increases at a fast speed that the total number of vehicles already reaches 327 million.Note that building a new XBL will reduce the road resource of the social vehicles,which impacts the road capacity,the traffic delay as well as the vulnerability of the transportation system.The limited road resources should be allocated appropriately between the buses and the social vehicles in a way that the priority of the buses can be maintained without harming the travel efficiency of the social vehicles too much.To achieve this,the concept of Bus Lane with Intermittent Priority(BLIP)are introduced.Analyzing the impact of BLIP on road capacity helps investigating the impacts on lane change behavior of social vehicles and patterns of traffic states.Furthermore,it can provide the traffic manager to design efficient policy to promote the BLIP.It has the significant and practical influence on improving the road traffic capacity and operational efficiency of XBL and reducing the negative impacts on the social vehicles.This study analyzes the characteristics of traffic state of urban roads,including the feature of traffic infrastructure,traffic management,traffic environment et al.Further,we study the characteristic of traffic flow such as traffic volume,speed and time headway et al.We analyzed the distribution of speed by vehicles class and type of lanes on urban roads.We also studied the time for which the bus enters and leaves the bus stations and corresponding dwell time based on real data.We demonstrate the relationship between the number of passengers get on and/or off the bus and the corresponding time duration.This study seek to analyze the relationships between the urban public transport and urban traffic flow in several dimensions,including the relationship between the traffic flow of public transportation and road capacity,and the relationship of traffic flow characteristics and the corresponding bus dwell time.Besides,the requirement and influence of installing BLIP is given.Those findings will be useful for modeling the urban traffic flow under BLIP.Considering the different car-following behavior of each vehicle pair,the Kruskal–Wallis test and Mann–Whitney U test methods are used to study the time headway,speed and accelerated speed.A modified NS model is proposed to prevent vehicle collisions and mitigate the impact of heavy vehicle on the following vehicles.We then develop a CP model by considering the vehicle-pair-based car-following model using Cellular Automaton(CA).Through error test,we evaluate the performances of the proposed CP model.Further,we compared the performance of the existing car following CA model.It shows that the proposed model is valid.Based on the CP model,this study can verify the BLIP-SCP model in context of two lanes on which the social vehicles giving way to bus on the BLIP.The simulation results show the main traffic flow characteristics of BLIP.The validity of the model is also verified.Based on the proposed CA model and lane change model,a numerical simulation approach is developed to study the road capacity of BLIP,the lane change behavior and its influence on the traffic flow.We seek to understand the discount rule of road capacity of BLIP and the conditions for which BLIP can be set.Results show that increasing clear distance and decreasing bus departure interval will reduce the road capacity of BLIP.The simulation results show setting BLIP can increase the speed of bus,decrease the running time of bus.It can realize bus priority without reducing the passenger capacity.Based on the DriverModel.DLL API in VISSIM,this study develops the external driver model by considering the rule of drivers in BLIP.We simulate the traffic flow in VISSIM using a real-world traffic network with explicit bus schedule,signal timing and traffic volume from Tucson city(Arizona)in American.By calibrating the incorporated parameters,verifying the index of traffic flow and running time in the simulation model,the simulation results are effective.We developed a VISSIM simulation model of BLIP.Based on the proposed VISSIM model with different clear distance,this study analyzes the performances of BLIP using two indicators,the bus average speed and the bus delay.We also study the impacts of BLIP on traffic flow such as traffic density,speed and delay.Based on these results,we provide reasonable clear distance.Simulation results shows that setting BLIP can increase the average speed and reduce the average delay of buses.But it will also increase the traffic density of the adjacent lanes,which decreases the average speed of the total network and slightly increases the average delay.This study shows that deploy a new BLIP has no influence on the total network capacity.Furthermore,while the longer clear distance enhances the bus priority,the negative influence on the network traffic flow will also be increased.Furthermore,the sensitivity analysis of the compliance rate of social vehicles changing lanes show the average speed and delay are affected by compliance degree of social vehicles drivers dramatically.Increasing the compliance degree can help improve the bus average speed and delay,but it has a little influence on the network traffic flow.The study results help the traffic operator to set right rules for planning,deploying,and analyzing the performance of BLIP.Furthermore,it gives the suggestions of improving the XBL and building new BLIP.Last,this study is useful to increase the attraction of buses and usage of road resource,increase the road capacity and mitigate the traffic jams.