2015 No. 4

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2015, (4) doi: 10.3963/j.issn.1674-4861.2015.04.001
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2015, (4) doi: 10.3963/j.issn.1674-4861.2015.04.002
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A Review and Prospects of Subsidy Mechanism for Bus Transit
ZHU Weiquan, XIE Binglei, YANG Xiaoguang, GE Hongwei
2015, (4): 1-8,53. doi: 10.3963/j.issn1674-4861.2015.04.001
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A scientific subsidy mechanism ensures the healthy development of bus transit industry,and the effec-tiveness and sustainability of government subsidy.This study reviews the research status,achievements,existing prob-lems and development prospects on the subsidy mechanism of bus transit in China.Firstly,the definition,research focus and challenges on the subsidy mechanism are reviewed.Secondly,the study summarizes the main methods,conclusions and problems on the research rationales,the calculation methods of bus transit subsidies,and the effects of subsidy and subsidy mechanism on bus performances.Finally,the research challenges are summarized and the future research trends and topics are identified including cost measurement method and establishment of subsidy mechanism.
A Study of Tolerant Waiting Time of Pedestrians at Signalized Intersections in Beijing
ZHANG Zhiyong, HAO Xiaoyun, WANG Dong, GONG Jian, WANG Da
2015, (4): 9-17. doi: 10.3963/j.issn1674-4861.2015.04.002
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Pedestrians are an important part of traffic at the signalized intersections.At present,the planning and design of the signalized intersections give priority to efficiency of the vehicles.In order to ensure the efficiency of the vehi-cles,many pedestrians crossing environments have been destroyed in Beijing."Chinese style of pedestrian crossing" was invented.Based on the characteristics of the current traffic in Beijing,this study focuses on the pedestrians who arrive at the signalized intersection crosswalk waiting area during the red light.A total of 9 554 pedestrians'waiting time were col-lected by both video survey and manual survey under the different conditions.This study develops a Cox hazard-based model of pedestrians'tolerant waiting time at signalized intersections.The result shows that the maximum tolerant waiting time of pedestrians is 52.88 s.The temperature,gender,age,travel time,red light time,traffic volume,length of cross-walks have great impacts on the pedestrians'tolerant waiting time,however land usage have no significant impacts on it.
An Algorithm for Identifying Main and Slow Flow Channels of Yangtze River
SHI Lei, CHU Xiumin, LIU Tong, LIU Huaihan, WANG Xiandeng
2015, (4): 18-24. doi: 10.3963/j.issn1674-4861.2015.04.003
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Vessels which navigate on the main flow channel can save energy.In order to more accurately divide the main and slow channels of the Yangtze River,this paper proposed methods of k-nearest neighbor algorithm and P-tile method.The improved P-tile method can avoid the main stream being too small by dynamic selection of P values.The k-nearest neighbor algorithm partitions the main and slow streams with channel hydrology information,such as depths and flow velocities.With the 1 1 sections'data of Yueyang and Jinkou measuring stations in Yangtze River,this study com-pared the partition results of these two algorithms.The results showed that areas of main and slow channels at the 10 out of 1 1 sections were close.A further comparison with the waterways at Longkou and Yanglinyan of the Yangtze River indi-cated the difference of the mainstream zone width estimated from the proposed algorithms was within 12% comparing to the actual,which can meet the requirements of the ship navigation.
A Capacity Analysis of Shared Bus/Car Lanes at Bottleneck Sections
TAN Zefang
2015, (4): 25-31. doi: 10.3963/j.issn1674-4861.2015.04.004
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In urban areas where space is preciously limited,bus lanes can be created only by the conversion of exist-ing general-use lanes.If buses depart at a low frequency,the bus lanes will be under-utilized and road space will be was-ted.At bottleneck sections,in particular,non-bus vehicles will suffer greater delays.The paper focuses on this issue by proposing bus/car shared lanes within the selected bottlenecks.A method to estimate the capacity of shared lanes is pro-posed while considering the impacts of cars.The intersection of Huanggang Road and Xincai Road in Shenzhen was simu-lated as a case study.The results indicate that the delays of cars decrease while the buses'level of service (LOS)remains unaffected when less than 20% cars drive into the shared lane.However,the LOSs for buses and cars both decrease when more than 20% of cars are in the shared lane The study also concludes that car traffic in the shared lane has a great impact on the bottleneck's capacity.The delays of cars increase exponentially as car volumes in the shared lane increases.
Effects of Countdown Timer onthe Type II Dilemma Zones
FU Chuanyun, ZHANG Yaping, LIAN Guan, HAO Siqi
2015, (4): 32-36. doi: 10.3963/j.issn1674-4861.2015.04.005
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Very few studies have investigated the distribution variation of the Type II dilemma zone under the condi-tion of with and without countdown timer at intersections,and the conclusions drawn to date are controversial.The objec-tive of this study is to further examine the effect of countdown timers on the Type II dilemma zone through videotaping vehicle movements at an unsignalized intersection.When the signal changes to yellow,the speeds and distances to the stop bar of the first vehicle stopped and the last vehicle passing through are measured and collected.Driving behavior under the two scenarios of with/without countdown timer is analyzed.A binary Logit regression is used to develop the stopping probability model under the two scenarios.The boundary of the type II dilemma zones is determined and the type II dilem-ma zones under the two scenarios are investigated.The results show that stopping probabilities increases when vehicles have longer distances from stop bar and/or with countdown timers;while higher vehicle speeds decrease the stopping like-lihood.The Type II dilemma zones move closer to the stop line when a countdown timer is installed,but its length is still 24.1 m.Therefore,countdown timers will not reduce the range of the Type II dilemma zones.However,in this study, the interaction effects of countdown timers and other variables are not considered during the process of determining the boundaries of the Type II dilemma zones,which will probably lead to underestimating the effectiveness of countdown tim-ers.
A Study of the Phase Setting of Exclusive Right-turn Signal under the Consideration of Vehicle Emission Characteristics
LI Zhenlong, DONG Wenhui, HAN Jianlong, ZHU Minghao
2015, (4): 37-42. doi: 10.3963/j.issn1674-4861.2015.04.006
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To alleviate the conflict between pedestrians and right-turn vehicles at the beginning of pedes-trian green light,the moving features of pedestrians and right-turn vehicles were investigated.A fixed-timed two-phase signalized intersection was taken as a case study in the paper.The impacts of the right-turn signal phase on the emission and average delay of vehicles were studied.The microscopic simulation software Vissim and the emission model based on VSP variables were combined to simulate different right-turn traffic volumes with three different pedestrian volumes be-fore and after implementing the exclusive right-turn signal phase.The exhaust emissions and average delays were analyzed respectively.The results indicate that the trend of vehicle emissions and average delays of before and after implementation are similar.The mean value of emissions is reduced by 9.46% and the mean value of average delays is reduced by 1 5.84%after implementation of the exclusive right-turn signal phase when the right-turn traffic volumes are below (61 5 ± 20) pcu/h.The average delays of right-turn vehicles decreased,but the exhaust emissions increased after right-turn signal im-plemented when right-turn traffic volumes are more than (61 5±20)pcu/h.
A Study on Following and Lane Changing Behaviors of Weaving Vehicles
CHEN Lilin, ZOU Zhijun, LI Xunhui
2015, (4): 43-48,118. doi: 10.3963/j.issn1674-4861.2015.04.007
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When failing to meet the conditions of changing lanes,the weaving vehicles will be forced to change lanes by squeezing the vehicles into the target lanes.This study analyzed the car-following & lane-changing (CF&LC)behav-iors of the weaving vehicles in depth.The influence factors of CF&LC behaviors were identified from the drivers'perspec-tive in order to establish the utility functions of CF&LC behaviors.A probability model of binary choice was also devel-oped in this study.The relevant variables of the models were investigated using the techniques of trajectory capture and calibrated by maximum likelihood estimation method.The effectiveness of the proposed models was verified by a case study.The results show that the proposed model can effectively simulate the CF&LC behaviors of weaving vehicles with a precision of up to 99.0%.
An Empirical Study for Identifying Traffic Breakdown at Bottlenecks
LI Xiaoqing, WANG Zhongyu, CHEN Kexin, WU Bing
2015, (4): 49-53. doi: 10.3963/j.issn1674-4861.2015.04.008
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Identification of traffic breakdown is critical for evaluating traffic flow states and making decision on traf-fic operation plan.In order to detect the differences of traffic conditions among the lanes in detail,a lane-based method is proposed,which is able to identify breakdown accurately and in an intuitive way.The occurring time of traffic breakdown is determined by enlarging the"turning point"of speed fluctuations at each time interval using speed transform cumulative curve.Compared to the traditional section-based and threshold-based methods,the proposed lane-based method is more accurate and objective which can not only differentiate the semi-congested states,where only some of lanes are congested, but also show the longitudinal and transverse propagation characters of traffic congestion in depth.The off-ramp at the Jungong Expressway Road in Shanghai is used as a case study and the results show that the breakdown actually occurs on the outermost lane firstly and then spread to innermost lane after an average of 4 minutes.When the congestion propa-gates to the upstream,the inner lanes tend to be more congested than the outer lanes.
A Safety Evaluation Model for Unsignalized T-Intersections Based on Conflict Probability
ZHANG Xiaoxiu, YANG Xiaoguang, ZHAO Jing
2015, (4): 54-60,68. doi: 10.3963/j.issn1674-4861.2015.04.009
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In order to evaluating the safety of the unsignalized T-intersections in a more objective way,this paper proposes a safety evaluation method after providing a detailed classification of intersections.The probability of traffic con-flicts is used as the evaluation index.In this paper,the average of traffic conflicts and its probability are described using a generalized linear model and Poisson distribution.In the generalized linear model,the average of the traffic conflicts is used as the explained variable while the conflict traffic flow rate as an explanatory variable.The traffic conflict probability of Poisson distribution is estimated based on the estimated average of conflict traffic.A simplified model is developed after the model parameters are calibrated based on the survey data.The effect of the through movements on main-street is sim-plified by an impact factor,which is divided into 4 levels based on the volumes.By analyzing the relationship between the calculated value of traffic conflict probability and the critical value of safety probability threshold,the safety of the unsign-alized T-intersections is evaluated.The feasibility and accuracy of the model is validated through actual cases.The results show that the traffic volumes of the turning movements have a greater effect on the safety than through movements.The study concludes that the volume of turning movements should be more carefully investigated than the volume of the through movements on main-road when using the proposed simplified model.The efficiency can be improved by 25% in average.
A Method of Identifying Serious Conflicts of Motor and Non-motor Vehicles during Passing Maneuvers
WANG Yaodong, CHEN Yuren
2015, (4): 61-68. doi: 10.3963/j.issn1674-4861.2015.04.010
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Since the existing traffic conflict techniques are not applicable to identify serious conflicts between vehi-cles and non-motor vehicles in China.And drivers'passing behaviors through the intersections are proven to play a signifi-cant role in the occurrence of traffic collisions.The study proposed a method of identifying serious conflicts between vehi-cles and non-motor vehicles in consideration of drivers'passing behaviors.The traffic scene videos were pre-processed by applying coordinate transformation technique,then the conflict data of vehicles and non-motor vehicles at the intersections was extracted.Critical time difference to collision (CTDTC)was proposed to depict drivers'passing behaviors.The results show that the difference of drivers'passing behaviors increases,which tend to trigger collisions,when the absolute value of TDTC is less than 0.66 s.The test results also indicate that the cumulative frequency of non-serious conflicts is about 1 5% and 85% for serious conflicts,which are confirmed by a cumulative frequency method,when 0.66 s of TDTC is de-fined as an identification threshold.The proposed method defines a specific threshold of identifying serious conflicts be-tween vehicles and non-motor vehicles and provides more accurate and objective results.
A Study of the Relationship between Crash Rate, Geometric Alignment and Freeway Safety
MENG Xianghai, JING Linpeng, HOU Qinzhong
2015, (4): 69-75,126. doi: 10.3963/j.issn1674-4861.2015.04.011
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A safety evaluation method for freeway segments is proposed in this study by analyzing the relationship between crash rates and road geometric alignment.First,the relationship between crash rates and road geometric features including radius of horizontal curves,deflections of horizontal curves,length of tangents,radius of vertical curves,longi-tudinal gradient is analyzed through linear regression.Then,the relationship between a combination of different alignment features and crash rates is studied.Further,the alignment factors analyzed over the first two steps are used to evaluate the impacts of geometric alignment features on crash rates and the method is then proposed to evaluate the safety of freeway. The results of a case study indicated that up to 81% of"dangerous highway sections" identified by proposed method are confirmed by the crash data.The proposed highway safety evaluation method is practical to identify collision prone sec-tions of freeways.
A Robust Video Detection Method for Traffic Incidents based on the Perception Theory of Dual Perspectives
XIN Le, CUI Hailong, FU Yuhao, XU Yongcun, YU Quan, CHEN Yangzhou
2015, (4): 76-81. doi: 10.3963/j.issn1674-4861.2015.04.012
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A new highway incident detection algorithm is proposed based on a perception theory of dual perspectives.The epi-polar plane image (EPI)features with each separate traffic lane were developed,which described the overall characteristics of traffic in each pre-defined lane.When fused with the separated behavior of each vehicle trajectories,the higher performance as well as lower complexity with algorithm is achieved based on the integrated dual perspective perceiving framework.Extensive experimental results with variety of typical traffic incidents (such as traffic congestion,retrograde driving vehicles,vehicle parking violations,and traffic collisions)showed that this new highway incident detection algorithm has the detection rate 94.09%,the false detection rate 4.51%, and the false negative rate1.40%.
A Study of the Relationship between Rescue Time and Survival Rate of Traffic Accidents on Freeways using A Cox Regression Model
YANG Huimin, CHEN Yuren, FANG Shouen, YUAN Jianhua
2015, (4): 82-86. doi: 10.3963/j.issn1674-4861.2015.04.013
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The rescue time of traffic collisions on expressways has a direct impact on traffic collision fatalities.Based on three consecutive years'collision records of an expressway in east China,the characteristics of rescue time were ana-lyzed in this paper.The impacts of rescue time on the survival rates were studied by using non-parametric estimation methods,and a survival-analysis model of the injuries was developed.Furthermore,factors of survival rates were ana-lyzed with Cox regression models.The results show that the survival rates of the injuries decrease with the increase of res-cue time.The survival rates can decrease to below 75% in about 14 minutes after the occurrence of collisions,so the inju-ries should be given necessary emergency rescue within 14 minutes.Meanwhile,further analysis of factors indicates the time of collisions is a risk factor of survival,and the risk of death in the nighttime is 3.46 times higher than in the day-time.
A Study of the Safety Margin of Continuous Descent Final Approach(CDFA)Based on Cloud Model
GAO Yang, HOU Yanchen
2015, (4): 87-92,126. doi: 10.3963/j.issn1674-4861.2015.04.014
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It is particularly important to study the safety margin of the continuous descent final approach (CDFA) as it has been widely used in China.This study analyzes the safety margin of the key steps in the process of CDFA,and a safety evaluation model is developed.On the basis of the literature reviews,the safety marge of CDFA is analyzed for the following:normal conditions,abnormal conditions and exchange of aircrew.This study proposes an index system model based on the relationship between the workload of the aircrew and safety margin.The parameters of the cloud model are calculated according to the related algorithm of the cloud model,and a distribution map of the cloud model was developed using Matlab.The results show that the interval values of the cloud model for the aircrew exchange range from 4.76~8. 99 during the CDFA process,which is significantly higher than those under the normal conditions and abnormal condi-tions.Therefore,the workload of the pilots who implements CDFA process will significantly increase when the problems arise during the aircrew exchange process.
An Assessment of the Conflict Risk of Converging Air Traffic using Monte Carlo Simulation
ZHENG Yue, SUI Dong, LIN Yingda, ZHANG Junfeng
2015, (4): 93-99. doi: 10.3963/j.issn1674-4861.2015.04.015
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In order to unveil the overall states and dynamic variation of conflict risks for converging air traffic,a conflict risk assessment method based on Monte Carlo simulation was proposed.Based on the analysis of the geometry characteristic of the converging airways,the conflict route segment model is proposed to determine the conflict ranges that are caused by converging air traffic.The conflict risk assessment method based on the Monte Carlo Simulation was designed.The conflict risks of converging air traffic were assessed from macroscopic and microscopic levels by comparing the 4D trajectories,conflict rate,conflict severity,conflict risk and total conflict risks.Finally,the conflict risks were as-sessed for the convergence of Route A593 and Route R343 at VMB by the simulation as an example based on statistical a-nalysis of historical operation data.
A Study of Ship Trajectory Restoration Based on Vondrak Filtering and Cubic Spline Interpolation
LIU Liqun, WU Chaozhong, CHU Duanfeng, CHEN Zhijun, SUN Chuan
2015, (4): 100-105. doi: 10.3963/j.issn1674-4861.2015.04.016
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Ship trajectories record the ship locations and times,which are significant for analyzing the navigation states and projecting maritime accidents.In order to correct the data errors of ship location and times due to AIS (auto-matic identification system)data transmission interruption and compensate the missing data of ship trajectories,this study proposed a ship trajectory restoration method.The study developed a distributive model of ship trajectories restora-tion by using Vondrak Filtering to smooth the navigation trajectories,and correcting the latitude and longitude informa-tion by using cubic spline interpolation,which formed the ship trajectories.The proposed restoration methods were veri-fied by Matlab under simulation.The results show that the algorithm error is 6.01×10 -5 and the proposed method can ac-curately restore ship trajectories.
A 4D Trajectory Planning method based on Historical Radar Tracks of Air Traffic
MA Guanghui, ZHANG Junfeng, WANG Fei, CHEN Qiang
2015, (4): 106-112. doi: 10.3963/j.issn1674-4861.2015.04.017
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4D trajectory planning can solve flight delay problems and accelerate the implementation and application of automation and intellectualization in Air Traffic Control.4D trajectory planning based on analysis of historical radar tracks was proposed.Historical radar tracks were clustered and analyzed by Dynamic Time Warping algorithm and Hier-archical clustering.Horizontal paths were designed based on the reproduced traffic flow and standard arrival routes.The ranges of altitudes and speeds of aircrafts were determined by statistical analysis of historical radar tracks.The altitude profiles were designed based on the principle of aircrafts should keeping high altitude as much as possible in the terminal area.Finally,the speed profiles which satisfy the scheduled time of arrivals were designed based on optimized parameters. Arrival flights to Shanghai Pudong Airport were selected as a simulation scenario as a result of the mean error of 2.5 s and the margin of error of 1.9‰.The simulation result indicates that the proposed 4D trajectory planning method can achieve flights landing punctuality,reduce flight delays and improve the efficiency of the terminal airspace.
A Warranty Analysis of Grade Separated Pedestrian Crossings of Urban Roadways
HAN Xianke
2015, (4): 113-118. doi: 10.3963/j.issn1674-4861.2015.04.018
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In order to set grade separated pedestrian crossing facilities reasonably on urban road sections and ensure the safety of crossing pedestrians,the video observation method was used to obtain the waiting time of crossing pedestri-ans,traffic conflicting times and driving speeds at an un-signalized crosswalk on an arterial road with two-way six lanes. Calculation formula of vehicle dispersing time was proposed,and the warrant of traffic volumes was defined for grade sep-arated pedestrian crossing facilities according to investigated threshold value of crossing pedestrians′ tolerable waiting time.Based on observed data,regression method was applied to establish relationship model between pedestrian-vehicle traffic conflicting times and vehicle driving speeds.The warrant of driving speed for grade separated pedestrian facilities was determined based on the relationship between stopping sight distances and the width of conflict zones.The warrant of pedestrian volumes was defined by calculated design capacity of signalized crosswalks.The results show that grade separa-ted pedestrian crossing facilities are warranted when vehicles’dispersing time of any direction is more than 60 s during one cycle in peak hour,or driving speed is more than 50 km/h,or crossing pedestrian volume is more than 2 200 person/(hg·m).
Spatial Optimization of the Logistics Network of Yunnan Province
HAO Jingjing, JI Xiaofeng
2015, (4): 119-126. doi: 10.3963/j.issn1674-4861.2015.04.019
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Logistics is an important supporting industry of the social and economic development.Reasonable spatial layout of logistics network can effectively promote the efficiency of regional logistics operation.A city logistics competitive measure index system was developed on basis of the four perspectives:economic development,logistics supply level,lo-gistics demand level and informationalized level.The logistics competitiveness of 1 6 cities in Yunnan province was evalua-ted by using principal component analysis of multi-source data.Based on the results of city logistics competitiveness meas-urement,the hub-and-spoke network model was used to optimize the logistics network in Yunnan province.The study concludes as follow:Firstly,Kunming,Qujing,Yuxi and Chuxiong as the center city,are the core of logistics hub-and-spoke network in Yunnan Province.A logistics circle of the city group is formed,which covers the whole Yunnan Prov-ince.Secondly,there are 1 1 cities including Zhaotong and Baoshan as the secondary nodes of cities,which have radiative surrounding county areas,where each county performances as tertiary logistics nodes.Meanwhile,the main and branch routes between each node are formed with the foundation of comprehensive transportation networks in Yunnan.The study also concludes that the hub-and-spoke logistics network structure has a high degree of spatial collaboration with the trans-portation networks in Yunnan,and it can effectively reduce logistics cost and improve the efficiency of logistics opera-tions.
Design and Implementation of the Vehicle Rear-End Collision Avoidance Terminal System Based on IEEE 802.11 p/1609
XU Shuyu, LU Hongyang, CHENG Jian
2015, (4): 127-132. doi: 10.3963/j.issn1674-4861.2015.04.020
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Rear-end collision is one of the main types of traffic collisions on the road.Therefore,rear-end collision avoidance technology has attracted extensive attention of numerous researchers around the world.This paper proposes a rear-end collision avoidance system based on the IEEE 802.1 1 p/1 609 protocols.The system consists of a Freescale hard-ware platform and a software platform based on an embedded Linux OS.Real-time location information of each vehicle is obtained by Global Positioning System (GPS).A wireless access in vehicular environments (WAVE)is used to provide a high-speed and two-way interactive communication between vehicles for real-time rear-end collision warnings.The per-formance of the system is tested.Test results show that the proposed system can provide high efficient and reliable com-munications between vehicles.The packet loss rate is less than 10% with Binary Phase Shift Keying (BPSK)under either static or dynamic vehicle operating state.And the results show that the system developed can effectively capture the dif-ferent driving behaviors and provide warnings in a real time with a high accuracy of 97%.The study results indicate that the proposed system is effective for field implementation.
2015, (4): 133-133. doi: 10.3963/j.issn.1674-4861.2015.04.023
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2015, (4): 134-134. doi: 10.3963/j.issn.1674-4861.2015.04.024
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