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    Decision-making Forum
    Determine Hub Port Location with Uncertain Demand and Cost
    ZHAO Xu, XU Hang, LIU Jiao
    2020, 20(3): 1-5. 
    Abstract ( )   PDF (337KB) ( )  

    This study focuses on the hub port location problem in the hub-and-spoke network. Multiple models were developed with consideration of the data change trends and the uncertainty of transportation demand and cost in the container shipping network. Considering the transportation links of the hub-and-spoke network, the study used a cost function to characterize the transportation costs between hub ports and developed a deterministic model for hub port selection. A stochastic model with uncertain demand was then developed for hub port selection with the discrete shipping demand. Next, a MINMAX method was used to develop a hub port location model with uncertain cost and actual data as input. Then the hub port location model was proposed with uncertain transportation demand and cost. The actual data of the European container transportation network was used to verify the model and solve the optimal choice of the hub port under various uncertain factors. A comparative analysis of the results was also included. This study provides a reference for the liner company to optimize the route.

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    Optimization and Analysis on Operating Strategies of Shared Autonomous Vehicles
    TIAN Li-jun, LIU Hui-nan, XU Yan
    2020, 20(3): 6-13. 
    Abstract ( )   PDF (510KB) ( )  

    With the coexistence shared autonomous vehicles(SAVs) and traditional vehicles, this paper studies how the SAV company optimizes its operating strategies with regards to different operational objectives and the influences on the commuters' travel mode choices. Provided that a certain number of solo commuters drive the traditional vehicles on the highway, and the other commuters without a car make travel mode choices between SAV and transit. This paper optimizes the operating strategies (i.e., the fare and capacity for SAVs) with the objectives changing from the total system cost or the net system benefit to the profit of the SAV company under the fixed demand and the elastic demand, respectively. The equilibrium mode-split flow, the optimal number of SAVs, the total system cost or the net system benefit, the profit for the company for SAVs, and other indicators are obtained. The equilibrium results are verified by a numerical example, and it is found that the monopoly SAV company always charges a higher fare and provides a smaller capacity. At the state of system optimum, the company for SAVs can't produce the positive profit and can only operate with the subsidy from the government.

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    Spatial Differentiation of Rail Transit and Urban Development Coordination: A Case Study of Beijing
    BAI Tong-zhou, CAI Le, ZHU Jia-zheng, LIN Xu
    2020, 20(3): 14-19. 
    Abstract ( )   PDF (374KB) ( )  

    To identify the spatial difference of the synergy degree of urban development level and rail transit passenger flow and the impact of urban development elements on rail transit passenger flow in different space areas, this paper introduced Moran's I describing the characteristics of spatial agglomeration and proposed an evaluation methodology of urban development level around rail transit stations. The study used the spatial agglomeration character of both urban development level and rail transit passenger flow as the synergy degree judgment standard and divided the study objective into several station groups. The Geographically Weighted Regression (GWR) model was utilized to evaluate spatial correlation of urban development level and rail transit passenger flow, as well as the impact of urban development elements on rail transit passenger flow. The case study shows that urban development level has significant impact on rail transit passenger flow in the area with high degree of coordination of these two parameters. The impact degree of urban development elements on rail transit passenger flow is as follows: the density has larger impact on rail transit passenger flow, followed by the convenience of transport interchange, the diversity of urban functions, and the compactness of development.

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    Forum about Comprehensive Transportation System
    Environmental Management Cost Prediction by Data Envelopment Analysis and Extended Belief Rule-based System for Transportation Industry
    YE Fei-fei, YANG Long-hao,WANG Ying-ming, LAN Yi-xin
    2020, 20(3): 20-27. 
    Abstract ( )   PDF (488KB) ( )  

    To address the environmental cost planning problem in transportation industry, an environmental management cost prediction model by data envelopment analysis (DEA) and extended belief rule-based (EBRB) system is proposed. The historical environmental input-output data is analyzed by the DEA model and applied for the reliability quantization of each rule; and an EBRB model that considers the rule reliability is established for environmental governance cost prediction of transportation industry. Finally, based on the data of transportation industry environmental management from 2004 to 2017 to verify the accuracy of the proposed model, and the results showed that the proposed model has higher accuracy than the existing cost prediction models. The investigation of this study can provide model support and reference for decision-makers.

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    Customer Demand Preferences' Heterogeneity of China Railway Express Based on Best Worst Method
    LI Qing-lin, PENG Qi-yuan, GUO Jing-wei, TANG Yin-ying, ZHANG Zhuo
    2020, 20(3): 28-32. 
    Abstract ( )   PDF (359KB) ( )  

    The rapid development of China Railway Express is facing the issue of insufficient transportation capacity along the route. This paper uses the Best Worst Method (BWM) based on market surveys to investigate the customer demand preferences of China Railway Express' service. A two-step cluster analysis was performed to reveal the heterogeneity of customer demand. The BWM results show that travel cost is overall the most important factor considered by the customers of China Railway Express. Compared with the transportation time and cost, improving the reliability is a recommended way for China Railway Express to develop its advantages. The twostep cluster analysis results show that optimizing the quality of transportation services would be beneficial to improve the existing transport capacity of China Railway Express.

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    Simulation Research of Urban Transportation Equity Based on General Equilibrium Theory
    ZHANG Chen-nan, ZHENG Ji-yang, YANG Zan
    2020, 20(3): 33-38. 
    Abstract ( )   PDF (381KB) ( )  

    Based on the general equilibrium model of urban space, this paper studies a transportation equity problem faced by high and low income groups under the condition of urban equilibrium with a multi- agent simulation approach. It constructs a site selection decision model for enterprises and individuals, and discusses the formation mechanism and influencing factors of the transportation equity problem by simulation, so as to provide a new research perspective for transportation equity. It is found that the high-income groups have priority over the low-income group in spatial selection. Low-income groups do not only need to accept lower level of wages, but also suffer higher commuting losses. Moreover, the difference in labor level and commuting speed have heterogeneous effects on the commuting loss of different groups. The widening of the capacity gap between the two groups will worsen the issue of transportation equity. When the efficiency of public transportation system is reduced, such as congestion, the commuting loss of low- income groups will increase significantly, and the transportation inequality is more serious.

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    Intelligent Transportation System and Information Technology
    3DCNN-DNN Based Traffic Status Prediction from Aerial Videos
    PENG Bo, TANG Ju, CAI Xiao-yu, XIE Ji-ming,ZHANG Yuan-yuan,WANG Yu-ting
    2020, 20(3): 39-46. 
    Abstract ( )   PDF (572KB) ( )  

    This study proposes a 3D Convolutional Neural Network- Deep Neural Network (3DCNN- DNN) method to recognize and predict traffic status from aerial videos. First, the roadway was divided into D sections and each section had an m - seconds video clip. The traffic state was recognized based on a typical 3DCNN structure named C3D (Convolutional 3D). Then, traffic state matrix Φ was established containing D road sections and ? historic time periods, and the traffic state prediction problem was transformed into a classification task with the input of Φ and output of limited number of traffic states. A model prototype for short time traffic state prediction was developed based on DNN. Traffic video sets were then assembled, and the DNN prediction prototype was tested and optimized through the number of hidden layers, neurons amount and training batch sizes. As a result, an optimal model named DNN* was proposed, which included 4 hidden layers with 64/128/128/64 neurons and training batch size of 64. The test results indicate that: C3D reaches an average F1 score of 95.71% to recognize traffic states from aerial videos. The prediction precision of DNN* is 91.18%, which has been improved by 6.86%, 57.85%, 62.26%, 26.47% and 43.14% compared to the DNN-Linear classification, K-Means, KNN (Knearest Neighbor), SVM (Support- vector Machines) and Linear classification respectively. The C3D is able to provide accurate traffic state matrix, and 3DCNN-DNN could effectively recognize and predict traffic state from road aerial videos.

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    Traffic Flow Prediction Based on Hybrid Deep Learning Under Connected and Automated Vehicle Environment
    LUWen-qi, RUI Yi-kang, RAN Bin, GU Yuan-li
    2020, 20(3): 47-53. 
    Abstract ( )   PDF (546KB) ( )  

    To achieve refined traffic flow prediction under connected and automated vehicle highway (CAVH) environment, this study proposes a lane- level traffic flow prediction model based on the hybrid deep learning (HDL). The proposed method takes the advantages of powerful data collection and calculation capability of the CAVH system. The HDL model divided the raw traffic speed series into several intrinsic mode function components and one residual component, and used the components as the input of the model. The bidirectional long short-term memory neural network and attention mechanism were used to establish the framework of the deep learning model. The lane-level speeds of the 2nd Ring road in Beijing, China were utilized to examine the accuracy and reliability of the proposed model. The results illustrate that the HDL model has ideal prediction performance at different types of lanes. Meanwhile, the prediction accuracy of the HDL model is significantly higher than that of previous models in terms of single-step-ahead prediction and multi-step-ahead prediction.

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    Short-term Traffic Flow Prediction of Multi-sections Based on Time-delay Modeling
    LIU Xiao-ming, TIAN Yu-lin, TANG Shao-hu, SHANG Chun-lin, WEI Lu
    2020, 20(3): 54-60. 
    Abstract ( )   PDF (505KB) ( )  

    In view of the existing traffic flow prediction methods failed to fully reveal the evolution rules of the traffic flow in multi- sections, this paper proposes a spatiotemporal correlation method based on traffic flow transmission delay modeling. This method introduces the similarity measure of traffic flow distribution in different traffic sections at different time, and constructs a spatial-temporal similarity matrix by segmenting the input data sequence of arrival vehicles. The delay parameters between adjacent sections are obtained. Based on the modeling of delay property, the traffic flow data between multi-sections is fused, and the traffic flow prediction is carried out by using the Long Short- Term Memory (LSTM) network. The validity and practicability of this method was verified by experimental analysis with actual traffic flow data.

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    Intelligent Vehicle Longitudinal Decision Making Based on Behavior Recognition
    CAO Bo, LI Yong-le, ZHAO Kai, ZHU Yuan
    2020, 20(3): 61-66. 
    Abstract ( )   PDF (433KB) ( )  

    This paper focuses on the longitudinal decision-making of intelligent vehicles. A method based on the degree of deviation from travel lane was proposed to identify the mode of vehicle in certain environment. Then, the longitudinal and transverse trajectory prediction model was developed considering dynamic traffic environment and being solved. The decision sets include maintaining, leading and avoiding behaviors of vehicle, and the proposed single vehicle decision method was based on the predicted trajectory. Then the comprehensive decision was made for three situations including acceleration, deceleration, and driving with constant speed and considering all dynamic environment. The real vehicle experiment shows that the average error of trajectory prediction in driving straight, lane changing, and making turns is 0.11 meters, 0.29 meters and 0.8 meters, respectively. The results show a high prediction accuracy. The proposed longitudinal decision- making methods can be used to improve the safety and comfort of intelligent vehicle driving under complex dynamic environment.

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    Improved Car-following Model Considering Mixed Traffic Flow on Queue Discharge at Signalized Intersections
    WANG Yi, RONG Jian, ZHOU Chen-jing,GAO Ya-cong, LIU Si-yang
    2020, 20(3): 67-74. 
    Abstract ( )   PDF (593KB) ( )  

    The Full Velocity Difference Model(FVD) had been calibrated and verified based on the real traffic data to reflect the car-following behavior of the mixed traffic flow at the intersection approach during the signal green time. However, the simulation results showed big gaps on acceleration, speed and vehicle spacing by using the FVD model. This study considered the differences of vehicle types and driver's behavior at four scenarios: car following car, car following bus, bus following car, and bus following bus, and then developed a new car-following model. The analysis results show that the performance of the proposed model has been significantly improved, and the Root Mean Square Percentage Errors (RMSPE) of speed and vehicle space are 15.29% and 22.32% , respectively, which are lower than the FVD model results. The improved model performs better than the FVD model in describing the car-following behavior at approaches of signalized intersections.

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    Signal Control Strategy and Benefit Analysis of Parallel Flow Intersection
    AN Shi, SONG Lang,WANG Jian, YANG Lu
    2020, 20(3): 75-82. 
    Abstract ( )   PDF (502KB) ( )  

    In order to solve the stopping problem of left- turning traffic at parallel flow interactions, this paper first proposes design schemes for the interactions to allow the left-turn, straight-going, and right-turn traffic flow in the one signal phase with all the traffic vehicles stopping at most one time. Two types of design schemes are proposed and compared with the existing design scheme. The parallel flow interaction with left-turn lanes placed on the right is focused on. Based on the characteristics of traffic flow, an optimization model is then constructed and some constraints are designed to avoid secondary stopping and conflicts of vehicles. The performance of the model is evaluated. The results show that compared with the traditional intersection control, the intersection capacity is increased by more than 60%, and the vehicle delay is reduced by about 70%. The proposed control strategy can eliminate the conflicts of left-turn and straight-going traffic and improve the intersection capacity of intersections without sacrificing the benefits of vehicles. This control strategy provides a new perspective for the study on parallel flow intersections.

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    BRT Priority Control Method Based on Two Stations at Intersection
    ZHANG Peng,WANG Peng-fei, SUN Chao, LIWen-quan
    2020, 20(3): 83-88. 
    Abstract ( )   PDF (345KB) ( )  

    BRT has a priority at intersections, which affects the traffic flow of other vehicles. A BRT priority control method is proposed for two-station intersections. This paper first describes the setting of the BRT double stations at the intersection and compares the single and double stations at the intersection in terms of the average BRT delay. Then, the BRT pre- stopping scheme and the driving schedule are proposed, according to the BRT departure time, the intersection signal timing, the average running speed, the intersection spacing, and the dwell time. In order to ensure that the BRT operates in accordance with the stopping scheme and schedule, a method is proposed by using BRT vehicle speed guidance and signal timing double compensation to correct the deviation of the actual departure time of the BRT from the timetable. Taking Changzhou BRT Line 1 as an example, five intersections are adopted to verify this method. The calculation results show that when the deviation range of BRT at the actual departure time of each station is ±5 s, ±10 s, ±20 s, the priority control method can significantly reduce the number and delay of BRT parking and improve the overall operational efficiency of BRT.

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    Regional Travel Demand Mining and Forecasting Using Car-hailing Order Records
    ZHANG Zheng, CHEN Yan-yan, LIANG Tian-wen
    2020, 20(3): 89-94. 
    Abstract ( )   PDF (430KB) ( )  

    This paper proposed a combined model that can fast mining traffic demand and prediction based on the Latent Dirichlet Allocation (LDA) analysis model. This combined analysis framework is able to deal with demand identification and prediction at the same time. The study first developed the traffic demand identification model at the traffic analysis zone (TAZ) scale for presenting the demand characteristics at both the spatial and temporal dimension.Then it proposed a prediction method under a multi-scale time window. The effectiveness and accuracy of the model was verified using car-hailing order data within Beijing's third-ring road. The results show that the model can identify and predict the regional travel demand under different time windows, and achieve good results.

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    Systems Engineering Theory and Methods
    Review of Traffic Data Collection Research on Urban Traffic Control
    WANG Dian-hai, CAI Zheng-yi, ZENG Jia-qi, ZHANG Guo-zheng, GUO Jia-lin
    2020, 20(3): 95-102. 
    Abstract ( )   PDF (368KB) ( )  

    Over the past few decades, urban traffic control technology has evolved to meet growing traffic demands and increasingly complex management objectives. As the basis of urban traffic control strategy and control algorithm, traffic data determines the applicability, reliability and advancedness of urban traffic control system. The development of data collection technology has brought opportunities and challenges to the improvement of urban traffic control. This paper reviews the basic methods of data collection and parameter estimation in traffic control systems. It analyzes the evolution of detection data methods from fixed unmarked detection data methods, probe vehicle- based data to fixed unique data. Combined with the probe vehicle- based data that emerged at the end of the 20th century, the impact of two corresponding traffic parameter estimation methods (stochastic method and shockwave-based method) are analyzed and reviewed. In view of the fixed unique detection data that has appeared in recent years, this paper analyzes the new tasks on urban traffic demand estimation and parameter estimation in traffic control. The paper then points out three directions of future trafficcontrol research in China: first, the information scope of urban traffic has been extended to regional and road network levels; second, with the evolution of data collection methods, the focus of traffic parameter estimation research has shifted to improving the real-time and accuracy of parameter estimation; third, there are gaps between the theory and practice in traffic parameter estimation. It is an important direction in urban traffic control research on how to use those methods and models to better guide the complex traffic control practice in China and consider the data error caused by the detection under different urban transportation environment, traffic flow arrival rules, and cross-interference between different types of traffic flows.

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    An Energy-efficient Timetable Optimization Method for Metro Operation Considering Spatial Distribution of Passenger Flow
    RAN Xin-chen, CHEN Shao-kuan, CHEN Lei, JIAWen-zheng
    2020, 20(3): 103-110. 
    Abstract ( )   PDF (551KB) ( )  

    Section passenger variation is a key factor to change the weight of metro trains which can affect their energy consumption and energy-efficient operation. An energy-efficient timetable optimization method incorporated with an unbalance spatial distribution of passenger flow is proposed for metro train operation under the dissipative regenerative braking mode. Based on the load variation and train motion equation, a timetable optimization model aiming at minimizing the net energy consumption is established to coordinate the temporal and spatial distribution of traction, cruising, coasting, and braking trains by adjusting their planned running times, dwell times, and turnaround times in a modest range. The dichotomy and particle swarm optimization algorithms are designed to solve the proposed model. The results from a case study based on one metro lines in Beijing show that the proposed method could effectively coordinate the energy-efficient operation of multiple trains. Besides, by considering the variation of section passenger flow, the timetable optimization model can further improve the energy-saving performance compared with the scheme that assumes the train load is constant.

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    Logistics Distribution Routing Optimization Based on Subway-freight Truck Intermodal Transportation
    ZHOU Xiao-ye, CUI Yao, HE Liang, MAXiao-yun,WANG Si-cong
    2020, 20(3): 111-117. 
    Abstract ( )   PDF (504KB) ( )  

    In order to alleviate traffic congestion and environmental pollution caused by distribution vehicles, subway- freight truck intermodal transportation services are designed. The subway services are used for freight transportation in the non- traffic peak hours with the fixed train service plan. Considering the constraints on the surplus capacity of subway trains, truck capacity, maximum truck driving distance, and customer service time windows, the logistics distribution routing optimization model is constructed to minimize the distribution distance. An improved adaptive genetic algorithm, which involves an irregular two-dimensional matrix coding structure, is proposed to solve the problem.The performance of the proposed model and algorithm is verified based on a real case in a city. The results show that the subway- freight truck intermodal transportation services can effectively improve customer satisfaction because of the high delivery rate within customer time windows and shorter distribution distance.

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    A Method for Expanding Station Carrying Capacity of High-speed Railway Based on Block Optimization Method
    LI Xiao-juan, YANG yang, HAN Bao-ming, JIAN Mei-ying
    2020, 20(3): 118-124. 
    Abstract ( )   PDF (366KB) ( )  

    The station carrying capacity is a key constraint of railway capacity. This paper increases the capacity of a station by reducing the influence of throat length on the interval time between the trains on the station. Based on the analysis of the principles and method of the division of station blocks, the relationship model of train routes and the calculation method of operation interval time are studied. Then, the simulation model and algorithm of station carrying capacity are established. The model takes the maximal number of trains allowed on the station as the objective function, and the model constraints include the interval time, the proportion of different train types, and the buffer time. Finally, a case study on a station verifies the effectiveness of the method. The proposed method in this paper can effectively increase the carrying capacity of high-speed railway stations.

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    Inefficiency of Mixed Traffic Equilibrium with Elastic Demand under ATIS
    YU Xiao-jun, LIU Zuo-zhi, SHU Ya-dong
    2020, 20(3): 125-129. 
    Abstract ( )   PDF (246KB) ( )  

    A transportation network is associated with the selfish users and the users with Advanced Traveler Information Systems (ATIS). The selfish users select their routes comply with user equilibrium principle and try to minimize their own travel cost. The users with ATIS select their routes comply with system optimum principle and advice to minimize the total travel cost in the system. This paper investigates the inefficiency of the mixed traffic equilibrium assignment with elastic demand under ATIS and based on the user's heterogeneities on different route choice principles. A variational inequality model for the mixed traffic equilibrium assignment is proposed and the upper bound of the inefficiency derived. The results show that the upper bound of the inefficiency depends on the ratio of user benefit and the total social surplus at traffic equilibrium assignment state. It also depends on the ratio of link flow by users with ATIS and the total link flow at traffic equilibrium assignment state.

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    Parking Spaces Renting and Allocation Model for Shared Parking
    SUN Hui-jun, FU Dan-hua, LV Ying, HENG Yu-ming, GUAN Tian-chao
    2020, 20(3): 130-136. 
    Abstract ( )   PDF (426KB) ( )  

    Shared parking is a new concept to alleviate parking issues and to make the most of the parking resources. However, the applications and operational strategies are still on the progress. The shared parking creates benefits by integrating parking resources, but renting the parking spaces also involves some costs. This study proposed an integer programming model to support making decisions to rent unused spaces and allocate parking requests. The model aims to maximize the profits in consideration of the parking spaces rental cost, parking serving income, and the potential loss caused by user rejections. The evaluation indexes were used to measure the effectiveness of the model. The results from numerical example show that the proposed model can effectively increase the profit and turnover rate. The model provides a theoretical reference for the decision management of shared parking.

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    Shared Parking Space Allocation Method Considering Reservation Demand
    ZHANG Shui-chao, CAI Yi-fei, HUANG Rui, ZHOU Zhu-ping
    2020, 20(3): 137-143. 
    Abstract ( )   PDF (448KB) ( )  

    This paper proposed a parking space allocation model to solve the parking allocation problem with reservation demand and the booking time, parking time and delay time are given. The profit of the system and walking distance users were set as the objectives. The demands were divided into basic request and delay request, and the model was then developed by collecting users' requests to determine the optimal allocation strategy. A random solution set generation method was proposed and a Monte Carlo algorithm was used to solve the problem. An example of a hospital and surrounding parking lots was used to test the model performance. The results illustrate that the proposed model can serve the parking space allocation problems and realize the balance between the system profit and user' demands.

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    Spatial Spillover Effects of Ports on Economic Growth of Hinterland Cities
    LIU Lin, YIN Feng
    2020, 20(3): 144-149. 
    Abstract ( )   PDF (286KB) ( )  

    This paper extends the research perspective of port-city relationship to the spatial dimensions. Using the 2003 to 2016 coastal ports and cities data in China and spatial panel model, this study empirically investigates the effects of ports on hinterland cities' economic growth. The results indicate that ports not only create intraregional spillovers, but inter-regional spillovers. The existence of port not only promotes the economic growth of the city where it locates, but also has a significant impact on the economic growth of hinterland cities. The spatial spillover impacts of port have increased significantly after the 2008 global financial crisis. The results of subregional test shows that the port around the Bohai Sea plays a significant role on promoting the economic growth of the city, but the spatial spillover effects of the port on hinterland cities are limited in the subregional test.

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    Equilibrium Analysis of High-occupancy Vehicle Lanes with Multi-class Commuters
    ZANG Guang-zhi, XU Meng
    2020, 20(3): 150-155. 
    Abstract ( )   PDF (390KB) ( )  

    The high-occupancy lane is an important traffic management plan that encourages carpooling, and thus achieves the ultimate goal of alleviating traffic congestion and improving traffic efficiency. This paper establishes a traffic system based on high-occupancy lanes, adding the impact of multi-class commuters with respect to additional carpooling cost and the urban rail transit mode. The mathematical programming model corresponding to the user equilibrium state and the system optimum state of the system is given, and the existence of the two states is proved. A numerical example is designed, and a comparison of user equilibrium state and system optimal state is carried out in the example. The results show that the traffic management department can significantly reduce the commute cost of commuters with low additional carpooling costs by developing a reasonable management plan. In other words, the management plan can improve traffic efficiency in the short term, while encouraging commuters to choose a lifestyle that is easy to carpool in the medium and long term to reduce the additional carpooling cost. In addition, by analyzing the length of the high- occupancy lane, it is found that the longer the length of the highoccupancy lane, the more significant the effect of the management scheme.

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    Optimizing Flexible Vehicle Scheduling for Single-line Battery Electric Buses
    TANG Chun-yan, YANG Kai-qiang, WU Na
    2020, 20(3): 156-162. 
    Abstract ( )   PDF (426KB) ( )  

    In electric bus scheduling, some electric buses may miss the time of consecutive trip due to long battery charging time, which normally lead to an increase in the use of buses. This study aimed to minimize the total operating cost of buses and developed a flexible electric bus scheduling optimization model. The model allows some buses to departure late but increase the number bus trips, and thus to reduce the number of operating vehicles and operating costs. A genetic algorithm was designed to solve the model. The study ranked bus trips in sequential order of the departure time to reduce the number of chromosomes, and to further improve the solution efficiency. A numerical experiment was performed and the results showed that the flexible electric bus scheduling method was able to significantly reduce the number of vehicles used, compared with fixed bus scheduling. The results also show that the delay time has a great impact on the total operating cost.

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    Dynamic Interaction of Urban Space Based on GPS Trajectory Mining
    FENG Hui-fang, ZHOU Dan-feng
    2020, 20(3): 163-168. 
    Abstract ( )   PDF (451KB) ( )  

    Mobility trajectory mining is essential to understand the characteristics of urban spatial dynamic interaction. This paper adopts the grid method to analyze the traffic volume between urban grids based on the taxi GPS trajectory in Lanzhou City. Given nodes that represent grids and link weights that define the traffic volume of connection between them, we establish the dynamic directed weighted complex network. The Infomap algorithm is used to identify the urban community, and the spatio- temporal evolution characteristics of city structure in Lanzhou are analyzed. The visualized analyses of the urban community are presented. The results show that there is a great difference in the spatial interaction of the rest and working days. The scope of spatial interaction on the working days is larger than the rest days. On the rest days, the space interaction scope is relatively small but the degree of fragmentation is relatively large. The urban spatial interactions are also different between peak and offpeak. Urban spatial interaction changes dynamically over time. The results can provide decision-making services for government management of cities, business operations, and residents' travel.

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    Bus Scheduling Optimization Model of Function-integrated Depot with Weaving
    CHEN Jian-kai,XIAO Liang,QIN Peng,HE Jia-li,LIU Qian,YANG Yu-qian
    2020, 20(3): 169-173. 
    Abstract ( )   PDF (300KB) ( )  

    Bus scheduling plays a key role on the operation of the stereoscopic and function- integrated depot (SFID or stereoscopic bus depot, SBD). Being different from previous bus scheduling, bus scheduling for SBD needs to determine the parking location, departure time, and driving path. This study focuses on the SBD bus scheduling considering the attributes of buses like departure in the morning and return at night. The condition of vehicle interweaving is also considered in the analysis. An optimization model is developed to solve the bus scheduling scheme based on the integer programming, and the weaving times between buses are set as the objectives of the model. The results indicate that there are two modes of bus scheduling for the SBD: the mode that dispatches buses at the same floor, and the mode that dispatches buses at different floors. The different- floor dispatching mode performs better than the same-floor dispatching mode. The interweaving condition is the doubleoverlapping of route space and out time. The case study was also conducted to verify the accuracy of the results and the feasibility of the proposed method.

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    Calculation Model of Bus Energy Consumption and CO2 Emission Based on Multi-source Data
    XU Long,WANG li, LIU Ying, SONG Guo-hua, LI Chen-xu, ZHAI Zhi-qiang
    2020, 20(3): 174-181. 
    Abstract ( )   PDF (532KB) ( )  

    The intensity of energy consumption and CO2 emission of buses are closely related to the vehicle type, bus routes and bus drivers. To accurately describe the characteristics of the intensity of energy consumption and CO2 emission, this study integrated multiple data resources for the analysis, which include the on-board diagnostic (OBD) monitoring data, diesel or liquefied natural gas (LNG) refueling data, and driver scheduling data. The strong linear relationship between the OBD monitoring data and the diesel or LNG refueling data indicated that the revised OBD monitoring data is able to meet the evaluation purposes. The Average Speed- Energy and CO2 Intensity Curve Model was developed, having a power function relationship with the goodness of fit ( R2 ) at 0.972 6. The empirical study in Beijing, China provides the following findings: when the average speed of the bus changes from 10 kilometers per hour to 60 kilometers per hour, the intensity of energy consumption and CO2 emission of LNG bus is 3.3% to 33.7% higher than that of the diesel bus, and the intensity of energy consumption and CO2 emission of double-decker bus are 2.4% to 13.3% higher than that of the articulated bus. When the same type of bus was used for different bus routes operating at the same average speed, the intensity of energy consumption can vary by 9.6%. The intensity can vary by 24.2% by different drivers on the same bus route. This study provides references for cities to set up the carbon emission target of bus energy consumption and CO2 emission with multiple data resources.

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    Dynamic Repositioning Model for Free-floating Bikesharing System Considering Shifting Demand
    LI Xing-hua, ZHANG Xin-yuan, CHENG Cheng, YANG Chao,WANGWei
    2020, 20(3): 182-189. 
    Abstract ( )   PDF (427KB) ( )  

    The spontaneous imbalance of the bike- sharing system creates an offset between the distribution of bikes and demands, and reduces the service capacity of the system. Bike reposition is needed to achieve rebalancing of the system. Existing dynamic reposition algorithms haven't considered the "re-take" demand during the trip due to insufficient supply at the origin. It is difficult to accurately identify the real distribution of requests and reposition effect was thus reduced. This paper proposed a bi-level programming model with user choice behavior as the lower layer and truck path planning as the upper layer. The heuristic algorithm with a simulator was used to solve the model. The case study was based on the historical data of Hongkou, Yangpu districts of Shanghai, China, and was grid- processed. The results show that the proposed model can effectively identify the shifting demand and improve the demand- supply matching level. The matching ratio has been improved by 18.07% to 19.89% under different reposition resource configurations, and the efficiency of bike- sharing system management has been enhanced to some extent.

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    Simulation of Crowding and Stampede on Evacuation Pedestrians in Pedestrian Facilities
    YUE Hao, LIU Qiu-mei, WU Xin-sen
    2020, 20(3): 190-197. 
    Abstract ( )   PDF (612KB) ( )  

    In this paper, a crowded pedestrian flow simulation model based on cellular automata and interaction forces is proposed to study the crowding and stampede. The model uses a single pedestrian to occupy multiple cell spaces and defines the rigid and elastic parts of a pedestrian to achieve the flexibility of pedestrians. And, the model describes interaction forces such as push- force and friction to describe the interaction between evacuated pedestrians. The simulation reproduces the phenomena of movement block, mutual extrusion, and continuous stampede. The simulation results indicate that, by increasing the pedestrian absorption coefficient and antistampede coefficient, the number of pedestrian injuries can be effectively controlled. The push-force accumulates to the top near the exits, where it may lead to stampede; and the stampede is lagging.

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    Chaotic Prediction of Flight Operation Risk Based on EEMD-ELM
    WANG Yan-tao, LI Jing-liang, GU Run-ping
    2020, 20(3): 198-205. 
    Abstract ( )   PDF (643KB) ( )  

    To developa reliable prediction methodon flight operation risk, according to the flight operation risk data of a certain airline in 2016-2018, through the reconstruction of phase space reconstruction for the time series, and the identification of series' chaos characteristics, an Extreme Learning Machine (ELM) based chaotic shortterm prediction model for flight operation risk was constructed combining with an iterative prediction method. The model then is improved by Ensemble Empirical Mode Decomposition (EEMD) threshold de-noising method. Finally, the risk prediction results are calculated, and the prediction accuracy of different methods is compared. The results show that the series has chaos characteristics. EEMD method can suppress modal aliasing of the IMF sequences. After EEMD threshold de- noising, the revised MAPE for the short forecast results is significant reduced. It is confirmed that the operation risk prediction method in the paper is applicable and effective.

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    Capacity Demand Prediction for En-route Airspace Based on Network Traffic Flow Dynamic Model
    CHEN Dan, YIN Jia-nan
    2020, 20(3): 206-211. 
    Abstract ( )   PDF (405KB) ( )  

    This paper proposes a prediction method for the future capacity demand of en-route sectors, which can be further used to airspace planning as traffic demand continues growing in the future. An en-route network traffic flow dynamic model, characterizing dynamics of traffic flow, is proposed to describe dynamic evolution process of traffic flow in the air route network. Then the yearly city-pair air traffic demand can be propagated into the entire en-route network, and the temporal and spatial traffic demand in the en-route airspace is obtained. On this basis, the future capacity demand of en- route airspace is predicted based on the time and space distribution of traffic demand in the network. A case study of two en- route sectors demonstrates the effectiveness of the proposed prediction framework The result indicates that the capacity demands of the two sectors will increase from 50 aircraft/h and 39 aircraft/h to 70 aircraft/h and 45 aircraft/h in the next 5 years.

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    Cases Analysis
    Analysis of Driver Mental Load on Helical Ramps and Helical Bridges Based on Naturalistic Driving Data
    XU Jin, LIU Xiao-ming, HU Jing
    2020, 20(3): 212-218. 
    Abstract ( )   PDF (653KB) ( )  

    To analyze drivers' mental load and the influencing factors when driving on the helical ramps and helical bridges, field driving tests using real passenger cars were conducted on four interchanges in a mountain city. The driver's ECG signals under the natural driving habits were collected by onboard instruments. Based on this naturalistic driving data, the relationship between heart rate amplitude, the RMSSD index overall distribution, and the ramp radius and slope were analyzed. The results indicated that the driving environment and horizontal curvature of the ramp, as well as the on-ramps junction and diversion, are the main factors of the mental load. The following, overtaking and meeting in the driving process all increase the driver's mental load. The driver's nervousness is higher when they are driving on uphill ramps than that on the downhill ramps. There is a strong negative correlation between the ramp radius and heart rate variability. Moreover, the unskilled driver is the most sensitive to the change of the ramp radius. There are two different correlations between ramp gradient and the heart rate variability: for unskilled drivers, the RMSSD increases linearly as the slope increases, while for the general and skilled drivers, their RMSSD profiles have a trend of high in the middle and low on both sides.

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    Unraveling Mobility Pattern of Dockless Bike-sharing Use in Shanghai
    FU Xue-mei, JUAN Zhi-cai
    2020, 20(3): 219-226. 
    Abstract ( )   PDF (507KB) ( )  

    Through the analysis of one-week records from Mobike in Shanghai, this study investigates the underlying mobility pattern of bike-sharing use behavior from a temporal perspective. The statistical results show a significant difference between weekdays-and weekends-cycling behavior. Two peaks are found within weekdays, while the biking trips are almost evenly distributed on weekends. The cyclers are classified into two and three groups for every day across weekdays and weekends, respectively, where each group is characterized by a distinctive distribution of biking start time and duration. Herfindahl-Hirschman Index (HHI) for the two combination, i.e., day-of-week-start time and day-of-week-duration, reflects high temporal regularity associated with bike-sharing use. And the larger standard deviation of HHI for the combination of day-of-week - start time confirms the flexibility of bicycling travel. This study is expected to unravel the mobility pattern of dockless bikesharing use, which could further contribute to its efficiency evaluation and system improvement.

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    Choice of Travel Mode for College Students Based on Family Attributes
    LUO Chen, LI Xiang, ZHONG Lin-feng, HU Shan-shan
    2020, 20(3): 227-232. 
    Abstract ( )   PDF (297KB) ( )  

    In order to analyze the influence of family attribute differences on college students' travel mode choice behavior, based on the disaggregate theory, a multivariate Logit model is constructed for college students' travel mode choice behavior. Based on the travel behavior surveys from 2 571 college studentsin Sichuan Province, the model parameters are calibrated using SPSS. The main family attribute factors affecting college students' travel choices are obtained, and the sensitivity analysis on the factorsis conducted. The results show that the average annual household income and economic net income have a significant impact on the choice of college students' travel modes. Compared with air transport, the average annual household income and economic net income have a greater impact on the choice of road transport and lower impact on rail transport. The discount ticketing form of grandparent purchasing tickets for their grandchildren can increase the probability that college students choose to travel by air.

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    Development of China Light-duty Passenger Car Test Cycle
    LIU Yu, WU Zhi-xin, LI Meng-liang, YU Han-zheng-nan,
    2020, 20(3): 233-240. 
    Abstract ( )   PDF (539KB) ( )  

    This paper presents the China Light- duty Passenger car Test Cycle (CLTC), developed under the "China Automobile Test Cycle Development" project. First, 16 million kilometers of driving data of light- duty passenger cars are collected from 41 cities nationwide in total, and the traffic volume data for each city are also collected to develop weighting factors. Then, the driving data and weighting factors are combined to develop unified speed- acceleration distributions representing the driving behavior in our country. Finally, based on the unified speed- acceleration distributions, the optimal short trip combination is selected by the chi- square test method and the China Light-duty Passenger car Test Cycle (CLTC) is constructed. Through the geo-information system (GIS) weighted results based on real data, the CLTC characteristics are compared with other typical cycles, and the comparison results demonstrate that CLTC conforms better to the reality in China.

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