The Effect Of Bus Stop Of Expressway On Taffic Operation Of Mainline

With constantly increasing travel demand, traffic congestion is getting worse in Chinese megacities, which seriously affects quality of urban life. Being important transportation corridor, urban expressway carries the large amount of traffic because of its high capacity and speed. Expressway operation intents to relieve traffic congestion and to enhance transportation level of service. However, many expressways in large cities are not functioning well due to frequently occurring traffic congestions.Traffic congestion on expressway can be caused by many factors including the location of bus stops. To promote public transit usage and take advantage of expressways’ high level of service, many bus routes use expressway as a part or entire service distance. The number of bus stops running is 68 on Third Ring Road in Beijing, for example. Due to their big physical dimensions and their acceleration/deceleration needs, buses’ maneuvering at a bus stop could significantly affect traffic flow of the expressway. Because of land use limitation and consideration on passenger mobility conveniences, most of bus stops are located near or at an access point(either on or off an expressway), even which is not recommended. The conflicts between buses entering/departing from a bus stop and other vehicles adversely affect capacity and flow efficiency of expressway.In this context, the bus stop on the urban expressway was chosen as the research object depending on the National Basic Research Program of China. This dissertation is aimed to investigate how traffic flow is affected by the bus stop location on the expressway. Specifically, the research was designed to find out how traffic operation characteristics(namely lane use distribution, capacity, traffic flow block) changes by bus stop located before and after an access point(either on or off the expressway). In order to alleviate traffic jam near the bus stop with the access, the traffic organization near a bus stop with an access was proposed. The main contents studied are as follow:Firstly, analysis of traffic characteristics of vehicles at the bus stop and the access on the expressway was conducted. Based on the analysis of traffic characteristics of vehicles at the bus stop, the confluence area of the bus stop, the characteristics of the merging and diverging vehicles at the access on the expressway, the weaving process of between buses and merging vehicles, diverging vehicles was considering according to bus stops location near the accesses. The traffic flow characteristics on the expressway near bus stop, entrance and exit were studied by collected data.Secondly, lane use distribution on the expressway near a bus stop, an entrance, an exit and a bus stop with an access was studied. The lane use distribution reflects the traffic volume on different lanes of road section at a single direction. It influences the stability of traffic flow and is an important factor of influencing road capacity. Based on the lane use distribution on the basic segment of expressway, the effect mechanism of buses entering and departing from the bus stop, vehicles merging and diverging from the mainline on the lane use distribution of expressway was analyzed. A series of nonlinear regression models on the lane use distribution of expressway near bus stop, entrance, exit, bus stop with access was developed based on collected data on the expressways in Beijing. The models were validated by survey data.Thirdly, the effect of the location of bus stops on the expressway capacity was analyzed. The capacity model on the expressway near the bus stop was developed based on queuing theory and considered bus bay stop with overflow and bus bay stops without overflow. The relationship between the expressway capacity and bus residence time, berth number and different priority were discussed respectively. Depending on a bus stop position to an entrance or exit ramp(upstream or downstream), the weaving process of between buses and merging vehicles or diverging vehicles was analyzed based on gap acceptance theory. The capacity models of the expressway were developed for four cases. A comparison of simulation experiment and model calculation was carried out. The relationship between the expressway capacity and bus arrival rate, merging or diverging volume, berth number were discussed respectively.Fourthly, the block influence of the location of bus stops on the traffic flow on the expressway was analyzed. The two kinds of vehicle delay models on the expressway with low and high flow volumes near the bus stop were developed based on the queuing theory and traffic wave theory. Vehicles delay of the expressway near an entrance includes merging delay and conflict delay. Vehicles delay of the expressway near an exit was determined based on the distance between diverging vehicles and following vehicles. To illustrate the block influence of the bus stop with the access on vehicles on the expressway, a bus stop located in the upstream of an exit was as an example. Survival analysis model of traffic flow was developed based on survival analysis theory and was used to determine the association between vehicle travel time and risk factors. The sensitivity analysis of individual variables such as traffic volume on the mainline, bus arrival rate and traffic at the exit was illustrated.At last, the traffic organization near the bus stop with an access was conducted. Many measures of traffic organization and control near the bus stop with an access were proposed from traffic system management, traffic demand management, traffic guidance and control. The space connection between the exit of expressway and the adjacent intersection was analyzed. Research has focused on the predication of traffic flow in the upstream of bus stops on the expressway included traffic guidance and control. A multi-step adaptive model of traffic flow based on chaos theory is established. In order to reveal chaos property of traffic flow on the expressway, a phase-space based on chaos theory on traffic flow time series was reconstructed. The C-C method was used to calculate the first embedding dimension and delay time. The G-P method was applied to calculate the correlative dimension of attractor. The largest Lyapunov exponent of traffic flow set was calculated based on the improved small data set method to verify the presence of the chaos in traffic flow time series. Based on the chaos characteristic in traffic flow time series of expressway and the short-term predictability of traffic flow time series and the adaptive tracking chaotic trajectory of adaptive algorithm, a novel multi-step adaptive prediction method was proposed to resolve the problem of adjusting the filter parameters of the chaos local adaptive prediction method during traffic flow multi- step prediction. The model was verified by collected data. It is helpful for traffic guidance and control near bus stops with accesses on the expressway.