Feasibility of Unconditional Transit Signal Priority Considering Delay Savings at Signalized Intersections: A Case Study of Dalian BRT Line No.1

AbstractActive transit signal priority (TSP) is a useful tool to remove or minimize control delay for buses at signalized intersections and consequently improve the performance of bus service. Conditional TSP has been proofed to be an effective measure with fewer impacts to non-prioritized traffic, and aroused increasingly research interests and implementation in European and North American cities nowadays. However, the implementation of conditional TSP requires a sophisticated mechanism for examining the schedule deviation of priority required buses, as well as scanning traffic operational conditions at network level. By contrast, unconditional TSP is a less costly and easier measure for implementation, because it gives priority to every required bus without considering its schedule deviation. The critical argument on unconditional TSP is its adverse impacts to non-prioritized traffic, particularly during peak hours. To determine the threshold for implementing unconditional TSP, in this paper, theoretical analysis based on signal display graphs of differential TSP granting strategies was undertaken to estimate delay savings and increments for prioritized and non- prioritized approaches respectively. In the next step, Dalian BRT line was taken as an example to verify the feasibility of unconditional TSP based on the proposed theory. Results show that unconditional TSP is feasible during off-peak hours, while for peak hours, feasibility of unconditional TSP mainly depended on the traffic volume of each approach

The Analysis Method of Capacity and Delay on Entrance Lane with Road-side Bus Lane

In order to reveal the traffic characteristics at signalized intersections with road-side bus lane, the analysis methods of capacity and delay at entrance lane were studied. Selecting a signalized intersection with road-side bus lane as investigation location, several traffic parameters were surveyed. Considering the traffic conflict between right-turn vehicles and through buses in this kind of entrance lane and based on the Gap Acceptance Theory, the calculation model of saturation flow rate, which is a key parameter both in the formulas of capacity and delay at signalized intersection mentioned in HCM2000, was improved. Using the investigation data, the calculation results of the traditional model and improved model were compared and analyzed. The research indicated that, comparing with common entrance lane, the capacity of right-turn lane at the entrance lane with bus lane should be reduced, and the travelling delay of bus lane and its inside adjacent lane should be increased. The degree of these effects is related to bus volume, right-turn volume and headway between buses

Analysis of Traffic Conflict Characteristic at Temporary Reversible Lane

In order to analyze the existing problems of temporary reversible lane, traffic conflict characteristic at the period of direction changing was analyzed. Taking Huangpu Road as the investigation object, the data of traffic conflict before and after direction changing were investigated respectively. By the method of mathematical statistics, the traffic conflict characteristic before and after direction changing were compared and analyzed. Using the method of regression analysis, the prediction model of traffic conflict was constructed. This paper also discussed the problem of utilization ratio of this kind of lane. The research showed that, in terms of traffic conflict of temporary reversible lane, there are obvious and regular differences between before and after direction changing. There is a certain relationship among the quantity of traffic conflict, flow and density. The problem of lower lane utilization ratio of temporary reversible lane usually exists

Uncertainty Evaluation of Indicative Polychlorinated Biphenyls in Fish by Gas Chromatography

In order to ensure the accuracy of laboratory test results, the uncertainty of the determination of indicative polychlorinated biphenyls in fish by gas chromatography was evaluated. According to the national Food Safety standard, National Food Safety Standard Maximum Levels of Contaminants in Foods (GB 2762-2022), the content of PCB28, PCB52, PCB101, PCB118, PCB138, PCB153 and PCB180) in the "measured" samples was determined as the total content of PCBs. Then, the polychlorinated biphenyls (PCBs) measurement model was re-established according to the "measured" and detection standard, and then the weight of uncertainty affected by the measurement model on test results were analyzed and evaluated. After evaluation, the measurement result of PCBs in quality control fish samples was 149.1 μg/kg, and the relative extended uncertainty was Ur=2.9%, k=2. The contribution of uncertainty was measurement repeatability 70.8%, sample weight 0.025%, internal standard volume 1.8%, sum of concentration ratios of each target in sample solution 27.3%

The Setting Method of Signal Timing Parameters at Over-saturated Intersection

In order to adapt to traffic operation situation of over-saturated signalized intersection, the setting methods of optimal cycle and green split of every phase are studied. Selecting Xinan Rd. and Wuyi Rd. intersection as study object, traffic investigation was carried out. Considering the two factors of the average delay and capacity at over- saturated intersection comprehensively, the optimization method of signal cycle length was proposed. Considering the traffic volume and queue length, setting method of the green splits of every phase was also proposed. Using the measured traffic data, signal timing scheme of the investigated intersection was not only designed, but also compared with the existing situation. The research indicates that, using this method, the average delay will be increased at over- saturated intersection, and the capacity can also be increased. This method is beneficial to reduce vehicles queuing at this kind of intersection

Nonlinear Stability of Natural-Fiber-Reinforced Composite Cylindrical Shells with Initial Geometric Imperfection Considering Moisture Absorption and Hygrothermal Aging

In this paper, the nonlinear stability of a natural-fiber-reinforced composite cylindrical shell with initial geometric imperfection is investigated. The nonlinear governing equations are established by high-order shear deformation theory. The load-edge shortening curves for different imperfection amplitudes are obtained by the Galerkin method. Several numerical examples are presented to verify the accuracy of the proposed method and to investigate the influence of initial geometric imperfection, moisture absorption, and hygrothermal aging on the post-buckling behavior of natural-fiber-reinforced composite cylindrical shells

Determination of Bus Crowding Coefficient Based on Passenger Flow Forecasting

To improve bus passengers’ degree of comfort, it is necessary to determine the real-time crowd coefficient in the bus. With this concern, this paper employed the RBF Neural Networks approach to predict the number of passengers in the bus based on historical data. To minimize the impact of the randomness of passenger flow on the determination of bus crowd coefficient, a cloud model-based bus crowd coefficient identification method was proposed. This paper first selected the performance measurements for determining bus crowd coefficient and calculated the digital characteristics of the cloud model based on the boundary values of the selected performance measures under six Levels-of-Service (LOSs). Then the subclouds obtained under the six LOSs were synthesized into a standard cloud. According to the predicted number of passengers in the bus, the passenger density and loading frequency were calculated, which were imported into the cloud generator to set up the bus crowd coefficient identification model. By calculating the crowd degrees of identification cloud and template cloud at each site, this paper determined the crowed coefficient of each bus station. Finally, this paper took the bus line No. 10 in Dalian city as case study to verify the proposed model. It was found that the crowd coefficients of the selected route ranged from 60.265 to 109.825, and the corresponding LOSs ranged between C and F. The method of discriminating bus crowding coefficient can not only effectively determine the congestion coefficient, but also effectively avoid the fuzziness and randomness of the crowding coefficient judgment in the bus, which has strong theoretical and practical significance