With the rapid development of urban road traffic and the increasing number of vehicles,how to alleviate traffic congestion is one of the hot issues that need to be urgently addressed in building smart cities.Therefore...With the rapid development of urban road traffic and the increasing number of vehicles,how to alleviate traffic congestion is one of the hot issues that need to be urgently addressed in building smart cities.Therefore,in this paper,a nonlinear multi-objective optimization model of urban intersection signal timing based on a Genetic Algorithm was constructed.Specifically,a typical urban intersection was selected as the research object,and drivers’acceleration habits were taken into account.What’s more,the shortest average delay time,the least average number of stops,and the maximum capacity of the intersection were regarded as the optimization objectives.The optimization results show that compared with the Webster method when the vehicle speed is 60 km/h and the acceleration is 2.5 m/s^(2),the signal intersection timing scheme based on the proposed Genetic Algorithm multi-objective optimization reduces the intersection signal cycle time by 14.6%,the average vehicle delay time by 12.9%,the capacity by 16.2%,and the average number of vehicles stop by 0.4%.To verify the simulation results,the authors imported the optimized timing scheme into the constructed Simulation of the Urban Mobility model.The experimental results show that the authors optimized timing scheme is superior to Webster’s in terms of vehicle average loss time reduction,carbon monoxide emission,particulate matter emission,and vehicle fuel consumption.The research in this paper provides a basis for Genetic algorithms in traffic signal control.展开更多
On the basis of the full velocity difference (FVD) model, an improved multiple car-following (MCF) model is proposed by taking into account multiple information inputs from preceding vehicles. The linear stability...On the basis of the full velocity difference (FVD) model, an improved multiple car-following (MCF) model is proposed by taking into account multiple information inputs from preceding vehicles. The linear stability condition of the model is obtained by using the linear stability theory. Through nonlinear analysis, a modified Korteweg-de Vries equation is constructed and solved. The traffic jam can thus be described by the klnk-antikink soliton solution for the mKdV equation. The improvement of this new model over the previous ones lies in the fact that it not only theoretically retains many strong points of the previous ones, but also performs more realistically than others in the dynamical evolution of congestion. Furthermore, numerical simulation of traffic dynamics shows that the proposed model can avoid the disadvantage of negative velocity that occurs at small sensitivity coefficients λ in the FVD model by adjusting the information on the multiple leading vehicles. No collision occurs and no unrealistic deceleration appears in the improved model.展开更多
With the development of the economy and the acceleration of urbanization, the number of vehicles in cities is increasing rapidly, which greatly increases the pressure on urban traffic. Solving traffic accidents and pr...With the development of the economy and the acceleration of urbanization, the number of vehicles in cities is increasing rapidly, which greatly increases the pressure on urban traffic. Solving traffic accidents and problems to keep smooth travel and safe travel has become a top priority in road construction. In this paper, how to optimize the traffic at the intersection of the urban road was discussed with the aim of reducing traffic accidents and problems to keep peoples’ smooth travel and safe travel.展开更多
In the paper the aim and meaning of traffic microscopic simulation is discussed first, and then three sub-models of the system are established, e. i. the model for random generation of the vehicles, the model for car-...In the paper the aim and meaning of traffic microscopic simulation is discussed first, and then three sub-models of the system are established, e. i. the model for random generation of the vehicles, the model for car-following and lane change influenced by an adjacent vehicle, and the model for control and optimization of intersection with signal. Optimization of the traffic signal timing with a genetic algorithm and a microscopic simulation is carried out. It represents a novel approach to solving optimal signal timing.展开更多
This paper considers the optimal traffic signal setting for an urban arterial road. By introducing the concepts of synchronization rate and non-synchronization degree, a mathematical model is constructed and an optimi...This paper considers the optimal traffic signal setting for an urban arterial road. By introducing the concepts of synchronization rate and non-synchronization degree, a mathematical model is constructed and an optimization problem is posed. Then, a new iterative algorithm is developed to solve this optimal traffic control signal setting problem. Convergence properties for this iterative algorithm are established. Finally, a numerical example is solved to illustrate the effectiveness of the method.展开更多
The effects of real-time traffic information system (RTTIS) on traffic performance under parallel, grid and ring networks were investigated. The simulation results show that the effects of the proportion of RTTIS usag...The effects of real-time traffic information system (RTTIS) on traffic performance under parallel, grid and ring networks were investigated. The simulation results show that the effects of the proportion of RTTIS usage depend on the road network structures. For traffic on a parallel network, the performance of groups with and without RTTIS level is improved when the proportion of vehicles using RTTIS is greater than 0 and less than 30%, and a proportion of RTTIS usage higher than 90% would actually deteriorate the performance. For both grid and ring networks, a higher proportion of RTTIS usage always improves the performance of groups with and without RTTIS. For all three network structures, vehicles without RTTIS benefit from some proportion of RTTIS usage in a system.展开更多
The delimitation of urban development boundaries plays an important role in optimizing the nation land space.“Double evaluation”is one of the important means to study and predict the scale of new construction land i...The delimitation of urban development boundaries plays an important role in optimizing the nation land space.“Double evaluation”is one of the important means to study and predict the scale of new construction land in the future and to determine the spatial distribution of urban construction land.This study combines the“double evaluation”with the FLUS(Future Land-Use Simulation)model to study the delimitation of the urban development boundary of Yichang.The results show that:(1)the“double evaluation”method comprehensively considers the carrying capacity of the resource environmental bear and the suitability of urban development;(2)the FLUS model can better couple the“double evaluation”method for Land Use/Land Cover(LULC)suitability evaluation,Land Use/land Cover Change(LUCC)simulation and urban development boundary delineation,and the overall accuracy of the simulation reaches 96%;(3)according to the requirements of relevant national policies,this study divides the urban development boundary of the study area into concentrated construction areas,elastic development areas and special purpose areas.This function-based division can meet the requirements of urban flexible development,ecological protection and urban safety.This research combines the FLUS model,which is widely used in the simulation of LUCC,with the double evaluation method used in China’s new round of land and space planning to obtain the result of the urban development boundary.This result is consistent with the existing plan of the study area.展开更多
A multi-objective improved genetic algorithm is constructed to solve the train operation simulation model of urban rail train and find the optimal operation curve.In the train control system,the conversion point of op...A multi-objective improved genetic algorithm is constructed to solve the train operation simulation model of urban rail train and find the optimal operation curve.In the train control system,the conversion point of operating mode is the basic of gene encoding and the chromosome composed of multiple genes represents a control scheme,and the initial population can be formed by the way.The fitness function can be designed by the design requirements of the train control stop error,time error and energy consumption.the effectiveness of new individual can be ensured by checking the validity of the original individual when its in the process of selection,crossover and mutation,and the optimal algorithm will be joined all the operators to make the new group not eliminate on the best individual of the last generation.The simulation result shows that the proposed genetic algorithm comparing with the optimized multi-particle simulation model can reduce more than 10%energy consumption,it can provide a large amount of sub-optimal solution and has obvious optimization effect.展开更多
The reduction of speed limits in urban roads through traffic calming schemes intends to ensure safer traffic conditions among road users by reducing the probability related to the occurrence of severe accident.Looking...The reduction of speed limits in urban roads through traffic calming schemes intends to ensure safer traffic conditions among road users by reducing the probability related to the occurrence of severe accident.Looking it from a different perspective,traffic calming measures can potentially resolve congestion problems at the same time by lowering the overall accessibility and attractiveness of private cars in urban areas.This study proposes a new methodological approach to explore and assess the direct impacts of traffic calming in the transport system efficiency of a metropolitan area.The multi-agent transport simulation(MATSim)and Open-Berlin scenario are utilized to perform this simulation experiment.By developing a new external tool,the free flow speed and road capacity of each network link is updated based on new speed limits and different compliance rates,which are defined per road hierarchy level.The test scenarios that are formulated present radical conditions,where the speed limit in most urban roads of Berlin drops to 30 km/h or even 15 km/h.The findings of this study show a considerably high increase in trips,passenger hours,and passenger kilometers using public transport modes,when traffic calming links are introduced,the reserve change is observed in private cars trips.Although the speed limits are decreased in inner urban roads in most of the scenarios,the decrease of average travel speed of private cars is not so high as it was expected.Surprisingly,private cars are used for longer distances in all test scenarios.Car drivers seem to use already existed motorways and private road to commute.In simulations,driver compliance to the new speed limits seems to be a determinant factor that is strongly influenced by the design interventions applied in a traffic calming area.展开更多
An improved multiple car-following model is proposed by considering the arbitrary number of preceding cars, which includes both the headway and the velocity difference of multiple preceding cars. The stability conditi...An improved multiple car-following model is proposed by considering the arbitrary number of preceding cars, which includes both the headway and the velocity difference of multiple preceding cars. The stability condition of the extended model is obtained by using the linear stability theory. The modified Korteweg-de Vries equation is derived to describe the traffic behaviour near the critical point by applying the nonlinear analysis. Traffic flow can be also divided into three regions: stable metastable and unstable regions. Numerical simulation is in accordance with the analytical result for the model. And numerical simulation shows that the stabilisation of traffic is increasing by considering the information of more leading cars and there is unavoidable effect on traffic flow from the multiple leading cars information.展开更多
The transformation of urban and building design into green development is conducive to alleviating resource and environmental problems.Building design largely determines pollutant emissions and energy consumption thro...The transformation of urban and building design into green development is conducive to alleviating resource and environmental problems.Building design largely determines pollutant emissions and energy consumption throughout the building life cycle.Full consideration of the impact of urban geometries on the microclimate will help construct livable and healthy cities.Computational fluid dynamics(CFD)simulations significantly improve the efficiency of assessing the microclimate and the performance of design schemes.The integration of CFD into design platforms by plug-ins marks a landmark development for the interaction of computer-aided design(CAD)and CFD,allowing architects to perform CFD simulations in their familiar design environments.This review provides a systematic overview of the classification and comprehensive comparison of CFD plug-ins in Autodesk Revit,Rhinoceros/Grasshopper,and SketchUp.The applications of CFD plug-ins in urban and building design are reviewed according to three types:single-objective,multi-objective,and coupling simulations.Two primary roles of CFD plug-ins integrated into the design process,including providing various micro-scale numerical simulations and optimizing the original design via feedback results,are analyzed.The issues of mesh generation,boundary conditions,turbulence models,and simulation accuracy during CFD plug-in applications are discussed.Finally,the limitations and future possibilities of CFD plug-ins are proposed.展开更多
Traffic interruption phenomena frequently occur with the number of vehicles increasing.To investigate the effect of the traffic interruption probability on traffic flow,a new optimal velocity model is constructed by c...Traffic interruption phenomena frequently occur with the number of vehicles increasing.To investigate the effect of the traffic interruption probability on traffic flow,a new optimal velocity model is constructed by considering the driver anticipation term in the interruption case for car-following theory.Furthermore,the effect of driver anticipation in the interruption case is investigated via linear stability analysis.Also,the MKdV equation is obtained concerning the effect of driver anticipation in the interruption case.Moreover,numerical simulation states that the driver anticipation term in the interruption case contributes to the stability of traffic flow.展开更多
In snow-icy road environment, the survey data indicate that the largest decrease in traffic flow running characters occurs when snow and ice begin to accumulate on the road surface. Saturation flow is decreased by 16%...In snow-icy road environment, the survey data indicate that the largest decrease in traffic flow running characters occurs when snow and ice begin to accumulate on the road surface. Saturation flow is decreased by 16%, speed is decreased by 30%, and start-up lost time is increased by 27%. Based on the signal control theory of HCM and Webster, the character values of traffic flow in different urban road environments were investigated, and the evolvement regularity of signal control parameters such as cycle, split, green time, offset, yellow time and red time in snow-icy road environment was analyzed. The impact factors and the changes in the scope of signal control parameters were achieved. Simulation results and practical application show that the signal control plan of road environment without snow and ice will increase the vehicle delay, stop length and traffic congestion in snow-icy road environment. Thus, the traffic signal control system should address a suitable signal control plan based on different road environments.展开更多
In this study, a new method for a comprehensive evaluation of air quality in urban agglomerations was developed based on a prototype used to solve the spatial Steiner-Weber point. With this method, the air quality inf...In this study, a new method for a comprehensive evaluation of air quality in urban agglomerations was developed based on a prototype used to solve the spatial Steiner-Weber point. With this method, the air quality information of each city in the city group is aggregated into an optimal gathering point, and then the air quality of the city group is then dynamically evaluated each year. According to the relevant data of the China Statistical Yearbook 2018, we applied this method to aggregate the air quality indices of the major cities in the Beijing-Tianjin-Hebei urban agglomeration from 2014 to 2017. Using the plant growth simulation algorithm (PGSA), the optimal assembly points were calculated to be of a higher accuracy, compared to the traditional mean value aggregation method. Finally, the air quality of the Beijing-Tianjin-Hebei urban agglomeration during each year was evaluated dynamically based on the obtained assembly points. The results show that the air quality of the urban agglomeration is ranked as follows: <span>Y2016<img src="Edit_28ddcae1-12ec-4d20-a4e9-77309c996766.bmp" alt="" /></span><span></span><span>Y2015<img src="Edit_5f164e96-55aa-4e37-98e1-6833665979d1.bmp" alt="" /></span><span></span><span>Y2017<img src="Edit_cfc0da49-7e3a-4aa8-82ac-ede99621d1ec.bmp" alt="" /></span><span></span><span>Y2014.</span>展开更多
近年来,极端天气事件发生频次不断增加,强度不断加大,其中,由暴雨引发的城市内涝导致交通应急事件发生概率进一步增大。为提升暴雨灾害下应急救援响应速度,本文开展应急车辆救援路径优化研究。以通行时间最短为目标,考虑路面积水对车辆...近年来,极端天气事件发生频次不断增加,强度不断加大,其中,由暴雨引发的城市内涝导致交通应急事件发生概率进一步增大。为提升暴雨灾害下应急救援响应速度,本文开展应急车辆救援路径优化研究。以通行时间最短为目标,考虑路面积水对车辆通行速度的动态影响,构建应急车辆救援路径优化模型,提出动态最短路径优化算法求解模型。选取上海市长宁区东北部作为研究区域,根据SWMM(Storm Water Management Model)模拟得到的50年一遇暴雨条件下城市道路路面的积水情况,设定应急救援场景,求解应急救援路径。通过本文提出算法求解得到的路径与传统静态最短路径算法求解结果对比可知,通行用时同比减少了25.42%。同时,考虑应急物资储备情况分配应急救援任务,扩展了算法的应用场景,形成可靠和高效的应急响应方案,可为提升暴雨灾害下应急响应效率提供参考。展开更多
基金supported by the joint NNSF&FDCT Project Number (0066/2019/AFJ)joint MOST&FDCT Project Number (0058/2019/AMJ),City University of Macao,Macao,China.
文摘With the rapid development of urban road traffic and the increasing number of vehicles,how to alleviate traffic congestion is one of the hot issues that need to be urgently addressed in building smart cities.Therefore,in this paper,a nonlinear multi-objective optimization model of urban intersection signal timing based on a Genetic Algorithm was constructed.Specifically,a typical urban intersection was selected as the research object,and drivers’acceleration habits were taken into account.What’s more,the shortest average delay time,the least average number of stops,and the maximum capacity of the intersection were regarded as the optimization objectives.The optimization results show that compared with the Webster method when the vehicle speed is 60 km/h and the acceleration is 2.5 m/s^(2),the signal intersection timing scheme based on the proposed Genetic Algorithm multi-objective optimization reduces the intersection signal cycle time by 14.6%,the average vehicle delay time by 12.9%,the capacity by 16.2%,and the average number of vehicles stop by 0.4%.To verify the simulation results,the authors imported the optimized timing scheme into the constructed Simulation of the Urban Mobility model.The experimental results show that the authors optimized timing scheme is superior to Webster’s in terms of vehicle average loss time reduction,carbon monoxide emission,particulate matter emission,and vehicle fuel consumption.The research in this paper provides a basis for Genetic algorithms in traffic signal control.
基金Project supported by the National High Tech Research and Development Program of China (Grant No 511-0910-1031)the National "10th Five-year" Science and Technique Important Program of China (Grant No 2002BA404A07)
文摘On the basis of the full velocity difference (FVD) model, an improved multiple car-following (MCF) model is proposed by taking into account multiple information inputs from preceding vehicles. The linear stability condition of the model is obtained by using the linear stability theory. Through nonlinear analysis, a modified Korteweg-de Vries equation is constructed and solved. The traffic jam can thus be described by the klnk-antikink soliton solution for the mKdV equation. The improvement of this new model over the previous ones lies in the fact that it not only theoretically retains many strong points of the previous ones, but also performs more realistically than others in the dynamical evolution of congestion. Furthermore, numerical simulation of traffic dynamics shows that the proposed model can avoid the disadvantage of negative velocity that occurs at small sensitivity coefficients λ in the FVD model by adjusting the information on the multiple leading vehicles. No collision occurs and no unrealistic deceleration appears in the improved model.
文摘With the development of the economy and the acceleration of urbanization, the number of vehicles in cities is increasing rapidly, which greatly increases the pressure on urban traffic. Solving traffic accidents and problems to keep smooth travel and safe travel has become a top priority in road construction. In this paper, how to optimize the traffic at the intersection of the urban road was discussed with the aim of reducing traffic accidents and problems to keep peoples’ smooth travel and safe travel.
文摘In the paper the aim and meaning of traffic microscopic simulation is discussed first, and then three sub-models of the system are established, e. i. the model for random generation of the vehicles, the model for car-following and lane change influenced by an adjacent vehicle, and the model for control and optimization of intersection with signal. Optimization of the traffic signal timing with a genetic algorithm and a microscopic simulation is carried out. It represents a novel approach to solving optimal signal timing.
基金Supported by the National Natural Science Foundation of China (10671045)
文摘This paper considers the optimal traffic signal setting for an urban arterial road. By introducing the concepts of synchronization rate and non-synchronization degree, a mathematical model is constructed and an optimization problem is posed. Then, a new iterative algorithm is developed to solve this optimal traffic control signal setting problem. Convergence properties for this iterative algorithm are established. Finally, a numerical example is solved to illustrate the effectiveness of the method.
文摘The effects of real-time traffic information system (RTTIS) on traffic performance under parallel, grid and ring networks were investigated. The simulation results show that the effects of the proportion of RTTIS usage depend on the road network structures. For traffic on a parallel network, the performance of groups with and without RTTIS level is improved when the proportion of vehicles using RTTIS is greater than 0 and less than 30%, and a proportion of RTTIS usage higher than 90% would actually deteriorate the performance. For both grid and ring networks, a higher proportion of RTTIS usage always improves the performance of groups with and without RTTIS. For all three network structures, vehicles without RTTIS benefit from some proportion of RTTIS usage in a system.
基金Natural Science Foundation of Hubei Province(No.2021CFB402)Key Laboratory of National Geographic Census and Monitoring,Ministry of Natural Resources(No.2020NGCMZD03)。
文摘The delimitation of urban development boundaries plays an important role in optimizing the nation land space.“Double evaluation”is one of the important means to study and predict the scale of new construction land in the future and to determine the spatial distribution of urban construction land.This study combines the“double evaluation”with the FLUS(Future Land-Use Simulation)model to study the delimitation of the urban development boundary of Yichang.The results show that:(1)the“double evaluation”method comprehensively considers the carrying capacity of the resource environmental bear and the suitability of urban development;(2)the FLUS model can better couple the“double evaluation”method for Land Use/Land Cover(LULC)suitability evaluation,Land Use/land Cover Change(LUCC)simulation and urban development boundary delineation,and the overall accuracy of the simulation reaches 96%;(3)according to the requirements of relevant national policies,this study divides the urban development boundary of the study area into concentrated construction areas,elastic development areas and special purpose areas.This function-based division can meet the requirements of urban flexible development,ecological protection and urban safety.This research combines the FLUS model,which is widely used in the simulation of LUCC,with the double evaluation method used in China’s new round of land and space planning to obtain the result of the urban development boundary.This result is consistent with the existing plan of the study area.
基金This work was supported by the Youth Backbone Teachers Training Program of Henan Colleges and Universities under Grant No.2016ggjs-287the Project of Science and Technology of Henan Province under Grant Nos.172102210124 and 202102210269.
文摘A multi-objective improved genetic algorithm is constructed to solve the train operation simulation model of urban rail train and find the optimal operation curve.In the train control system,the conversion point of operating mode is the basic of gene encoding and the chromosome composed of multiple genes represents a control scheme,and the initial population can be formed by the way.The fitness function can be designed by the design requirements of the train control stop error,time error and energy consumption.the effectiveness of new individual can be ensured by checking the validity of the original individual when its in the process of selection,crossover and mutation,and the optimal algorithm will be joined all the operators to make the new group not eliminate on the best individual of the last generation.The simulation result shows that the proposed genetic algorithm comparing with the optimized multi-particle simulation model can reduce more than 10%energy consumption,it can provide a large amount of sub-optimal solution and has obvious optimization effect.
文摘The reduction of speed limits in urban roads through traffic calming schemes intends to ensure safer traffic conditions among road users by reducing the probability related to the occurrence of severe accident.Looking it from a different perspective,traffic calming measures can potentially resolve congestion problems at the same time by lowering the overall accessibility and attractiveness of private cars in urban areas.This study proposes a new methodological approach to explore and assess the direct impacts of traffic calming in the transport system efficiency of a metropolitan area.The multi-agent transport simulation(MATSim)and Open-Berlin scenario are utilized to perform this simulation experiment.By developing a new external tool,the free flow speed and road capacity of each network link is updated based on new speed limits and different compliance rates,which are defined per road hierarchy level.The test scenarios that are formulated present radical conditions,where the speed limit in most urban roads of Berlin drops to 30 km/h or even 15 km/h.The findings of this study show a considerably high increase in trips,passenger hours,and passenger kilometers using public transport modes,when traffic calming links are introduced,the reserve change is observed in private cars trips.Although the speed limits are decreased in inner urban roads in most of the scenarios,the decrease of average travel speed of private cars is not so high as it was expected.Surprisingly,private cars are used for longer distances in all test scenarios.Car drivers seem to use already existed motorways and private road to commute.In simulations,driver compliance to the new speed limits seems to be a determinant factor that is strongly influenced by the design interventions applied in a traffic calming area.
基金Project supported by the Natural Science Foundation of Hunan Province,China (Grant No. 07JJ6106)the Important Project of Scientific Research Foundation of Hunan University of Arts and Science,China (Grant No. JJZD0902)the Fund of the 11th Five-year Plan for Key Construction Academic Subject of Hunan Province,China (Grant No. 06GXCD02)
文摘An improved multiple car-following model is proposed by considering the arbitrary number of preceding cars, which includes both the headway and the velocity difference of multiple preceding cars. The stability condition of the extended model is obtained by using the linear stability theory. The modified Korteweg-de Vries equation is derived to describe the traffic behaviour near the critical point by applying the nonlinear analysis. Traffic flow can be also divided into three regions: stable metastable and unstable regions. Numerical simulation is in accordance with the analytical result for the model. And numerical simulation shows that the stabilisation of traffic is increasing by considering the information of more leading cars and there is unavoidable effect on traffic flow from the multiple leading cars information.
文摘The transformation of urban and building design into green development is conducive to alleviating resource and environmental problems.Building design largely determines pollutant emissions and energy consumption throughout the building life cycle.Full consideration of the impact of urban geometries on the microclimate will help construct livable and healthy cities.Computational fluid dynamics(CFD)simulations significantly improve the efficiency of assessing the microclimate and the performance of design schemes.The integration of CFD into design platforms by plug-ins marks a landmark development for the interaction of computer-aided design(CAD)and CFD,allowing architects to perform CFD simulations in their familiar design environments.This review provides a systematic overview of the classification and comprehensive comparison of CFD plug-ins in Autodesk Revit,Rhinoceros/Grasshopper,and SketchUp.The applications of CFD plug-ins in urban and building design are reviewed according to three types:single-objective,multi-objective,and coupling simulations.Two primary roles of CFD plug-ins integrated into the design process,including providing various micro-scale numerical simulations and optimizing the original design via feedback results,are analyzed.The issues of mesh generation,boundary conditions,turbulence models,and simulation accuracy during CFD plug-in applications are discussed.Finally,the limitations and future possibilities of CFD plug-ins are proposed.
基金the National Natural Science Foundation of China(Grant Nos.61963008 and 61673168)the Natural Science Foundation of Guangxi Zhuang Autonomous Region,China(Grant No.2018GXNSFAA281274)+1 种基金the Doctor Scientific Research Startup Project Foundation of Guangxi Normal University,China(Grant No.2018BQ007)the Innovation-Driven Development Special Fund Project of Guangxi Zhuang Autonomous Region,China(Grant No.GUIKEAA19254034).
文摘Traffic interruption phenomena frequently occur with the number of vehicles increasing.To investigate the effect of the traffic interruption probability on traffic flow,a new optimal velocity model is constructed by considering the driver anticipation term in the interruption case for car-following theory.Furthermore,the effect of driver anticipation in the interruption case is investigated via linear stability analysis.Also,the MKdV equation is obtained concerning the effect of driver anticipation in the interruption case.Moreover,numerical simulation states that the driver anticipation term in the interruption case contributes to the stability of traffic flow.
基金Sponsored by the National Basic Research and Development Program of China(Grant No.2006CB705505) Research Fund for the Doctoral Program of Higher Education of China(Grant No.200802131012)
文摘In snow-icy road environment, the survey data indicate that the largest decrease in traffic flow running characters occurs when snow and ice begin to accumulate on the road surface. Saturation flow is decreased by 16%, speed is decreased by 30%, and start-up lost time is increased by 27%. Based on the signal control theory of HCM and Webster, the character values of traffic flow in different urban road environments were investigated, and the evolvement regularity of signal control parameters such as cycle, split, green time, offset, yellow time and red time in snow-icy road environment was analyzed. The impact factors and the changes in the scope of signal control parameters were achieved. Simulation results and practical application show that the signal control plan of road environment without snow and ice will increase the vehicle delay, stop length and traffic congestion in snow-icy road environment. Thus, the traffic signal control system should address a suitable signal control plan based on different road environments.
文摘In this study, a new method for a comprehensive evaluation of air quality in urban agglomerations was developed based on a prototype used to solve the spatial Steiner-Weber point. With this method, the air quality information of each city in the city group is aggregated into an optimal gathering point, and then the air quality of the city group is then dynamically evaluated each year. According to the relevant data of the China Statistical Yearbook 2018, we applied this method to aggregate the air quality indices of the major cities in the Beijing-Tianjin-Hebei urban agglomeration from 2014 to 2017. Using the plant growth simulation algorithm (PGSA), the optimal assembly points were calculated to be of a higher accuracy, compared to the traditional mean value aggregation method. Finally, the air quality of the Beijing-Tianjin-Hebei urban agglomeration during each year was evaluated dynamically based on the obtained assembly points. The results show that the air quality of the urban agglomeration is ranked as follows: <span>Y2016<img src="Edit_28ddcae1-12ec-4d20-a4e9-77309c996766.bmp" alt="" /></span><span></span><span>Y2015<img src="Edit_5f164e96-55aa-4e37-98e1-6833665979d1.bmp" alt="" /></span><span></span><span>Y2017<img src="Edit_cfc0da49-7e3a-4aa8-82ac-ede99621d1ec.bmp" alt="" /></span><span></span><span>Y2014.</span>
文摘近年来,极端天气事件发生频次不断增加,强度不断加大,其中,由暴雨引发的城市内涝导致交通应急事件发生概率进一步增大。为提升暴雨灾害下应急救援响应速度,本文开展应急车辆救援路径优化研究。以通行时间最短为目标,考虑路面积水对车辆通行速度的动态影响,构建应急车辆救援路径优化模型,提出动态最短路径优化算法求解模型。选取上海市长宁区东北部作为研究区域,根据SWMM(Storm Water Management Model)模拟得到的50年一遇暴雨条件下城市道路路面的积水情况,设定应急救援场景,求解应急救援路径。通过本文提出算法求解得到的路径与传统静态最短路径算法求解结果对比可知,通行用时同比减少了25.42%。同时,考虑应急物资储备情况分配应急救援任务,扩展了算法的应用场景,形成可靠和高效的应急响应方案,可为提升暴雨灾害下应急响应效率提供参考。