Research On Pedestrian Traffic Characteristics And Safety Evacuation In Integrated Transport Transfer Hub

Since more than thirty years of the Reform and Opening-up Policy, the transportationinfrastructure construction has risen to a new height in our country. And it is becoming a newdevelopment trend to build the Integrated Transportation Hub System (ITHS) whichintegrates various transport modes into a mass ITHS. The Integrated Transportation TransferHub (ITTH), as the key node and the center of Integrated Transportation Systems, is thecollection point of multiple transportation modes and the distribution center of all types ofpassenger in ITTH. With the sustained and rapid increasing of passengers in the ITTH, as wellas some other characteristics including closed environment, intensive traffic flow andcomplex transfer relationship, the ITTH’ safety problems gradually emerged. The facility hasbecome a hub with the higher and more unexpected accident frequency. Once the emergenciesoccur, it will easily cause heavy casualties and property losses, and will cause a tremendousnegative impact to society at the same time. Therefore, how to organize and manage the trafficflow inside the ITTH and achieve the safe-effective evacuation for passengers is becoming theurgent mission to be solved. Based on this, we proposed our insight on the pedestrian trafficflow characteristics and their safety evacuation issues following the research order of“Perception-Identification-Evacuation”. On one hand, we hope we can provide an importanttheoretical basis for the pedestrian flow traffic characteristics and traffic flow theory. On theother hand, the research will have an important practical significance for the safety evacuationunder emergency conditions.Since the passengers are the principal part in the ITTH, the design goal of Urban MetroHubs (UMHs)(Declaration: The ITTH proposed in the paper mainly refers to UMHs) is tomeet the requirements of pedestrian largely. Therefore, through the pedestrian traffic datacollection experiment design in the ITTH, it is necessary to study the pedestrian trafficcharacteristics in the UMHs deeply and firstly. We conducted the field observation andcamera survey in the North Street comprehensive transfer hub in Xi’an metro to collectmacroscopic traffic parameters (speed, flow, density, and occupancies), and then explore thepedestrian behavior patterns and pedestrian traffic characteristics in the comprehensivetransfer terminal. We dealt with a total of17,771sample data through SPSS and MATLAB, the relations among the4parameters are depicted and tested by means of the curve fit. Thefitting results shows that, the average walking speed of pedestrians is1.114(m/s) in theNorth Street comprehensive transfer hub in Xi’an metro, which is lower than the averagerates in other domestic and foreign cities. The relation between the density and the speed inthe terminal complies with linear laws, and pedestrian speed decreases with the densityincreasing. The relationship between flow and density complies with a cubic equation, whichis not entirely symmetrical around. With the density of pedestrian increasing, the flow firstlyincreases and then decreases, showing a parabolic form. The results can enrich the basic datafor comprehensive transfer terminal planning, and can provide a reliable evidence for thetransportation design and safety evacuation in the terminals.In order to find the rules between the service level and the pedestrian subjectiveperception in the UMHs, A Structural Equation Mode (SEM) is promoted to quantify thelevel of service and reflect the pedestrian of subjective perception. Firstly, based onpedestrian subjective perception, the UMHs service level questionnaire is designed tomeasure the passengers’ satisfaction in Xi’an North Street comprehensive transfer hub. Andthe main factors affecting subjective perception of pedestrian and the law of pedestrianperceive service level in the UMHs are found. Secondly, based on pedestrian’s securitydemand, comfort needs, convenience demand and service demand, quantitative analysis of theUMHs service level is calculated by SEM model. Meanwhile interactions between subjectiveperceptions and its relationship with ITH are researched. This research can provide thetheoretical basis and reference for optimization design in the UMHs and play an importantrole in the designing of service function.On the basis of pedestrian traffic characteristic in the UMHs, we analyzed theconnotation and metrics criterion of the pedestrian crowd, and we also analyzed the fuzzinessand randomness in UMHs. In the end, we propose a Crowd Automatic Identification Model(CAIM) based on Cloud Model (CM). The CAIM puts the pedestrian speed, density, flow andaverage headway as its input, which regards the service level classification in the “TransitCapacity and Quality of Service Manual2ndEdition” as its primary standard. According totheir boundary value under different service levels to determine the digital characteristics ofthe cloud, we use the cloud synthesis theory to establish template cloud which is attached to different level of service, and then, we input the survey data (speed, density, occupancies,flow, headway, et.al) into the cloud generator with the purpose of setting up the cloud identifymodel. According to the definition of cloud similarity, we calculated the identify cloud andtemplate cloud similarity in the channel, the stairs and platforms, further identified the state ofthe6levels of service. Moreover, the crowded degree is defined independently, which isdescribed in a quantificational level under the state of crowded degree in the UMHs. Finally,on the basis of pedestrian crowding identification, the early warning and control strategy ofpedestrian crowded degree are put forward.Safety evacuation is the important strategy for the pedestrian congestion control. On thebasis of automatic crowd degree identification in the UMHs, we elaborate the pedestrianevacuation characteristics in the view of time, analyzed the factors of pedestrian safetyevacuation and finally established the model of safety evacuation for pedestrian in theUMHs. Evacuation time is a significant safety coefficient for UMHs. Usually, a reasonablemodel for evacuation time can effectively promote the safety for pedestrian when emergencyincidents occur in UMHs. In this paper, we propose a pedestrian evacuation time model forUMHs to improve the accuracy and reliability of its evacuation time. Firstly, we design anexperiment survey based on the multiple video sequences to analyze the characteristics ofpedestrian flow. Then, we decompose the evacuation process on the basis of the parameters,which involve the evacuation characteristics, the speed-density variation law, the pedestriandrop-off time, the platform evacuation time and the channel evacuation time. Finally, we tookthe Xi’an North Street comprehensive transfer hub as an example, and verified the feasibilityof the proposed pedestrian evacuation time model. The result shows that the relative error forthe evacuation time between the experiment result and the actual data is low and hence it canprovide a good theoretical guidance for innovating the evacuation efficiency and the designreasonability in the UMHs.At the same time, we put our sight on the emergency evacuation path of optimal routechoice in the UMHs from the perspective of space. In order to explore the optimal routechoice of emergency evacuation in UMHs, according to the brittle characteristics of UMHssystem and ant colony algorithm, we propose a novel method of emergency evacuation routechoice in UMHs based on improved ant colony algorithm. Passengers’ optimum and worst routes of emergency evacuation in Xi’an North Street comprehensive transfer hub is simulated.The simulation results show that the length of best and worst route of emergency evacuationbetween the starting point and8exits can be obtained by adjusting the value of importance oftrip distance and degree of conformity, when the relative importance of pheromoneconcentration to graph G unchanged. The optimum route of emergency evacuation in urbanUMHs can be easily obtained when the importance of trip distance above5and the degree ofconformity above0.3, and when the importance of trip distance above5and the degree ofconformity below0.5, the route of emergency evacuation is the worst.