Bus-stop Capacity Considering Berth Layouts And Dwelling Organization Maneuvers

Public transport is an important component of urban transport system. Transit priority policies are necessary requirements of improving the service level of public utilities, releaseing traffic jam and changing the urban development way. Bus stops are the most common infrastructures in urban public transit system and play a great influence on the service quality and operational efficiency of the whole bus transit system. However, the bus-stop operation reality is subject to two aspects, including design levels and management measures. That is to say, different berth layouts and dwelling organization maneuvers will lead to the change of bus-stop capacity.To improve the traffic efficency and avoid the large-scale queueing phenonmenon at bus stops, this dissertation develops the bus-stop capacity calculation method under different queueing conditions, based on the improved classical queueing models and state transition diagram behavior models. To highlight the mechanism of berth reaction and berth utilization, the operational results and applicable conditions of buffer allocation and exit maneuvers are analyzed. Moreover, the influence factors of bus-stop capacity are discussed and the change trends are explained. Main works of this dissertation are summarized as follows:(1) According to the saturation value of queueing systems, the bus-stop queueing state can be classified into under-saturated state and near-saturated state. Under-saturated bus-stop capacity is decided by the vehicle capacity of platforms and berths. However, near-saturated bus-stop capacity is related to the carrying capacity of facilities and the maximal discharge flow that can be achieved at stops of different berth number and layout forms is explored.(2) A numerical model is proposed to estimate the under-saturated bus-stop capacity considering the berth clearance time and failure rate. The model is used to reflect the variations of berth pooling and blocking effects. Take two typical bus stops and two common dwelling ways for example, the change trends of bus-stop capacity caused by bus arrival rates, boarding and alighting passengers and interflow delay are analyzed. Accordingly, the saturated capacity and influence thresholds under different berth layouts and dwelling organization maneuvers are compared.Results show that bus-stop capacity exhibits the exponential growth trend with the increase of arrival rate and has a power function decline with the increasing number of boarding and alighting passengers. In addition, the relationship between bus bay capacity and interflow delay accords with the quadratic function. The fixed-dwelling way will decrease the efficiency of bus queueing system. Compared to free-dwelling, bus-stop capacity achieves saturated value in advance and the influence thresholds are lower than free-dwelling ways.(3) A calculation model is presented to estimate the near-saturated bus-stop capacity applying the behavior modeling methods of state transition diagram and timeline event graph. The model is used to reveal the coupling linkage effects among multi-berth and the influence of berth layout property. And the conception of vehicle-holding buffer between dual-platform at the same bus stop is described. The Monte Carlo Method is adopted to calculate the bus-stop capacity and bus delay. Results show that the buffer helps decline the berth blocking effect to some extent. The applicable conditions of different berth layouts and buffer design length are given for reference. When the dwell time coefficient of variation changes in a specific range (0.4-0.8), with the increases of the buffer length, the capacity of two tandem berths increases. While the capacity of three tandem berths and four tandem berths have no increment with the longer buffer and the buffer with space for holding a single vehicle is suitable.(4) Given the proper limited-overtaking exit discipline, an analytical model applying the small propability event judgment is formulated to predict the near-saturated bus-stop capacity under limited-overtaking maneuvers. The threshold conditions and consequences of exit maneuvers are explored. The model is used to explain the two influence aspects on capacity, including exit delay and vacated berths. For two tandem berths, when the dwell time coefficient of variation is more than 0.6 and there are no holding vehicles in the buffer, the limited-overtaking scheme produces sizable gains in capacity. For four tandem berths, the limited-overtaking scheme will in many instances retard the maximum rates that buses can discharge from busy stops due to the frequent appearance of vacated berths. Compared to earlier work, the effect of exit maneuvers on road traffic in this model is less and that is the reason why the threshold conditions are more strict.