At road intersections, pedestrians are frequently exposed to high level of air pollutants, and th... more At road intersections, pedestrians are frequently exposed to high level of air pollutants, and the effective estimation is thus critical for relieving the health risk in such a microenvironment. Although a series of deterministic models have been used to estimate the concentrations of air pollutants at intersections recently, they are limited to the original purpose of most simulation models to simulate the average behavior of the dispersion process of vehicular pollutants at longer time scale such as daily and hourly. While pollutant levels can vary with traffic signal lights and instantaneous peaks occur between minutes, these models are thus confronting the trial of forecasting minute-scale pollution levels. Hence, this study first evaluates the performances of two typical air quality models, i.e., California Line Source Model with Queuing and Hot Spot Calculations (CAL3QHC) and California Line Source Model version 4 (CALINE4), in predictions of fine particulate matter (PM2.5) and carbon monoxide (CO) at 5-min scale. Results show that CAL3QHC generally performs well for 5-min predictions of both PM2.5 and CO compared with CALINE4. Besides, both models perform better at off-peak than peak periods, which can be attributed to the fluctuation of high traffic volumes as well as the more complex mechanical turbulence induced by passing vehicles in peaks. Furthermore, performances of both models are more related to wind speed particularly when predicting CO concentrations. When wind speed is less than 1m/s, both models will have better performances. The outputs of these findings demonstrate the potential of both models to be applied to forecast the real-time trends of air pollution as well as to capture the extreme values due to varied scenarios at road intersections.
2012 4th International Conference on Intelligent Human-Machine Systems and Cybernetics, 2012
ABSTRACT The introduction of UAV into transportation offers a great number of challenges such as ... more ABSTRACT The introduction of UAV into transportation offers a great number of challenges such as how to utilize the collected vehicle data of different levels to obtain traffic variables. Meanwhile, different detection approaches may acquire different types and precisions of vehicle data, and the methods that will be chosen for each detection approach also may vary. The main objective of this paper is to compare the difference of several methods of calculating space mean speed (SMS), so as to provide guidance for SMS calculation and application based on various detection data of UAV. Two basic methods and three expanded methods that are possible to be used for UAV detection to calculate SMS of a road are discussed based on a dataset from NGSIM. Without considering the errors that may be caused by instability of UAV flight and video processing, differences among the methods are analyzed in the MatLAB software. The results of the two basic methods are of large difference, and the expanded methods used to estimate the SMS in various time periods will also generate different results. So when the results obtained by these methods are used for data fusion and other transportation applications, they should be assigned different weights. Some other results are obtained too, which may provide references for the traffic parameter extraction based on UAV detection, and the data fusion between the space mean speed from UAV detection and that from other traffic detection methods.
URISA Journal s Wiggins, Deuker, Ferreira, Merry, Peng, Spear 51 The Dimensions of the Applicatio... more URISA Journal s Wiggins, Deuker, Ferreira, Merry, Peng, Spear 51 The Dimensions of the Application Challenge: Transportation Planning and Management Choices about transportation alternatives permeate our daily lives. We are accustomed to making quite sophisticated decisions ...
2009 IEEE/INFORMS International Conference on Service Operations, Logistics and Informatics
... case of high-speed rail system in Taiwan which showed that an optimal set of ... They also fo... more ... case of high-speed rail system in Taiwan which showed that an optimal set of ... They also formulated a multi-class mixed-equilibrium mathematical program to capture the route choice behaviors ... and his co-authors (2007) presented an on-line timetable for rescheduling method in ...
Public health emergencies are characterized by significant uncertainty and robust transmission, b... more Public health emergencies are characterized by significant uncertainty and robust transmission, both of which will be exacerbated by population mobility, threatening urban security. Enhancing regional resilience in view of these risks is critical to the preservation of human lives and the stability of socio-economic development. Network resilience (NR) is widely accepted as a strategy for reducing the risk of vulnerability and maintaining regional sustainability. However, past assessments of it have not sufficiently focused on its spatial effect and have overlooked both its internal evolution characteristics and external threats which may affect its function and effectiveness. Therefore, we used the Yangtze River Delta Region (YRDR) as a case study and conceptualized an integrated framework to evaluate the spatial pattern and mechanisms of NR under the superposition of the COVID-19 pandemiv and major holidays. The results indicated that the topology of a population mobility network ...
Traffic monitoring with infrastructure-based sensors is effective and reliable for improving traf... more Traffic monitoring with infrastructure-based sensors is effective and reliable for improving traffic safety and traffic monitoring on high-volume roads, but not on low-volume roads. Low-volume roads in remote areas lack traffic monitoring sensors and thus traffic incidents are difficult to detect in a timely manner. Hence, this paper focused on low-volume road, and introduced Unmanned Aerial Vehicle (UAV) to detect traffic incident and analyzed its feasibility. Firstly, the research aim and definition of traffic incident were presented. Then, a numerical simulation method of using UAV to detect traffic incident was proposed, and a simulation case study with sensitivity analysis was implemented. Next, a UAV flight experiment was conducted. Finally, the cost-benefit analysis of using UAV to detect incident was given. The simulation results showed: (1) the theoretical UAV incident detection rate of the given scenario was 8.80%; (2) extending incident detection time, conducting UAV shuttling flight can increase incident detection rate significantly; and (3) some factors, such as UAV detection range, UAV flight speed and road incident occurrence rate, had little impact on incident detection result. The experiment and cost-benefit analysis showed that it’s cost efficient to use UAV to detect incident for low-volume road.
Road edges recognition is important for various applications in Intelligent Transport System . Th... more Road edges recognition is important for various applications in Intelligent Transport System . This paper focuses on extracting road edges from an image captured by a Unmanned Aerial Vehicle. Linear feature extraction is an important part of this job which is done by a proposed chain-code based algorithm. This paper brings forward a novel direction encoding scheme (DES) which improves encoding efficiency of digital straight lines and overcome drawbacks of Freeman encoding scheme (FES) successfully. DES also simplifies chain-code based line detecting methods from four stages to three. The new DES chain-code based criteria proposed can extract line segments in O(n) time, and curb errors due to digitalization effectively. A rotation of line (ROL) approach is employed for grouping line segments into much longer ones. Experimental results show that algorithm proposed in this paper works pretty well for road edges extraction
International Conference on Transportation Engineering 2009, 2009
Giving priority to transit vehicles at urban intersections could improve transit operation and sc... more Giving priority to transit vehicles at urban intersections could improve transit operation and schedule reliability and attract ridership, it may also be an effective way to alleviate traffic congestion. This paper reports a new method to compute the cycle length at signalized intersections based on the principle of people oriented transportation systems. This is a departure from the current signal timing mechanism based on the average delay per vehicle, which is naturally in favor of private vehicles. Taking the minimum delay per person as the objective and based on the linear programming planning, the author developed a model calculating the optimal cycle length. Furthermore, the model was calibrated and validated in a case study. The result shows that, comparing with traditional control program, the model not only reduced delay per person but also diminished the delay per car dramatically at the same time. It demonstrated that giving priority to bus not only improve bus services but also improve all traffic at urban intersections.
Transportation Research Record: Journal of the Transportation Research Board, 2001
The use of breakeven analysis as a tool to assess the benefits of intelligent transportation syst... more The use of breakeven analysis as a tool to assess the benefits of intelligent transportation systems (ITS) at the system level in systemwide sketch planning is discussed. The breakeven analysis was developed on the basis of the SCRITS (SCReening for ITS) spreadsheet template and used data from Madison, Wisconsin, as a case study and provided considerable in sight into the magnitude of the potential benefits of different ITS programs. The analysis can help identify critical performance variables in the assessment of ITS benefits. Breakeven analysis coupled with sensitivity analysis can be used to identify and assess ITS projects for deployment in the ITS planning and programming process with limited data. It can be used to screen, prioritize, and select ITS projects among different ITS options. It can also be used to compare ITS projects in different geographic locations on the basis of different traffic data and breakeven points. The method is also useful in the identification of da...
2013 21st International Conference on Geoinformatics, 2013
ABSTRACT This paper analyzes characteristics of population distribution and movements of the city... more ABSTRACT This paper analyzes characteristics of population distribution and movements of the city of Shenzhen in southern China by using mobile phone position data, and visualizes the distribution and movements of population in Shenzhen. Nowadays, positioning information of calling activity records of cell phones is more and more feasible with popularity of cell phones and development of the cell network. The tremendous advantages of positioning data in massive data samples, real-time and coverage guarantee it can be a significant supplement tool to monitor population dynamics. The experimental results display a vivid visual representation of population distribution and their movements through space and time. This paper's analytical method and results can potentially contribute to a better understanding of the surrounding city and further benefits to urban planning and management.
ABSTRACT In recent years, the increasing development of traffic information collection technology... more ABSTRACT In recent years, the increasing development of traffic information collection technology based on floating car data has been recognized, which gives rise to the establishment of real-time traffic information dissemination system in many cities. However, the recent massive construction of urban elevated roads hinders the processing of corresponding GPS data and further extraction of traffic information (e.g., identifying the real travel path), as a result of the frequent transfer of vehicles between ground and elevated road travel. Consequently, an algorithm for identifying the travel road type (i.e., elevated or ground road) of vehicles is designed based on the vehicle traveling features, geometric and topological characteristics of the elevated road network, and a trajectory model proposed in the present study. To be specific, the proposed algorithm can detect the places where a vehicle enters, leaves or crosses under elevated roads. An experiment of 10 sample taxis in Shanghai, China was conducted, and the comparison of our results and results that are obtained from visual interpretation validates the proposed algorithm.
At road intersections, pedestrians are frequently exposed to high level of air pollutants, and th... more At road intersections, pedestrians are frequently exposed to high level of air pollutants, and the effective estimation is thus critical for relieving the health risk in such a microenvironment. Although a series of deterministic models have been used to estimate the concentrations of air pollutants at intersections recently, they are limited to the original purpose of most simulation models to simulate the average behavior of the dispersion process of vehicular pollutants at longer time scale such as daily and hourly. While pollutant levels can vary with traffic signal lights and instantaneous peaks occur between minutes, these models are thus confronting the trial of forecasting minute-scale pollution levels. Hence, this study first evaluates the performances of two typical air quality models, i.e., California Line Source Model with Queuing and Hot Spot Calculations (CAL3QHC) and California Line Source Model version 4 (CALINE4), in predictions of fine particulate matter (PM2.5) and carbon monoxide (CO) at 5-min scale. Results show that CAL3QHC generally performs well for 5-min predictions of both PM2.5 and CO compared with CALINE4. Besides, both models perform better at off-peak than peak periods, which can be attributed to the fluctuation of high traffic volumes as well as the more complex mechanical turbulence induced by passing vehicles in peaks. Furthermore, performances of both models are more related to wind speed particularly when predicting CO concentrations. When wind speed is less than 1m/s, both models will have better performances. The outputs of these findings demonstrate the potential of both models to be applied to forecast the real-time trends of air pollution as well as to capture the extreme values due to varied scenarios at road intersections.
2012 4th International Conference on Intelligent Human-Machine Systems and Cybernetics, 2012
ABSTRACT The introduction of UAV into transportation offers a great number of challenges such as ... more ABSTRACT The introduction of UAV into transportation offers a great number of challenges such as how to utilize the collected vehicle data of different levels to obtain traffic variables. Meanwhile, different detection approaches may acquire different types and precisions of vehicle data, and the methods that will be chosen for each detection approach also may vary. The main objective of this paper is to compare the difference of several methods of calculating space mean speed (SMS), so as to provide guidance for SMS calculation and application based on various detection data of UAV. Two basic methods and three expanded methods that are possible to be used for UAV detection to calculate SMS of a road are discussed based on a dataset from NGSIM. Without considering the errors that may be caused by instability of UAV flight and video processing, differences among the methods are analyzed in the MatLAB software. The results of the two basic methods are of large difference, and the expanded methods used to estimate the SMS in various time periods will also generate different results. So when the results obtained by these methods are used for data fusion and other transportation applications, they should be assigned different weights. Some other results are obtained too, which may provide references for the traffic parameter extraction based on UAV detection, and the data fusion between the space mean speed from UAV detection and that from other traffic detection methods.
URISA Journal s Wiggins, Deuker, Ferreira, Merry, Peng, Spear 51 The Dimensions of the Applicatio... more URISA Journal s Wiggins, Deuker, Ferreira, Merry, Peng, Spear 51 The Dimensions of the Application Challenge: Transportation Planning and Management Choices about transportation alternatives permeate our daily lives. We are accustomed to making quite sophisticated decisions ...
2009 IEEE/INFORMS International Conference on Service Operations, Logistics and Informatics
... case of high-speed rail system in Taiwan which showed that an optimal set of ... They also fo... more ... case of high-speed rail system in Taiwan which showed that an optimal set of ... They also formulated a multi-class mixed-equilibrium mathematical program to capture the route choice behaviors ... and his co-authors (2007) presented an on-line timetable for rescheduling method in ...
Public health emergencies are characterized by significant uncertainty and robust transmission, b... more Public health emergencies are characterized by significant uncertainty and robust transmission, both of which will be exacerbated by population mobility, threatening urban security. Enhancing regional resilience in view of these risks is critical to the preservation of human lives and the stability of socio-economic development. Network resilience (NR) is widely accepted as a strategy for reducing the risk of vulnerability and maintaining regional sustainability. However, past assessments of it have not sufficiently focused on its spatial effect and have overlooked both its internal evolution characteristics and external threats which may affect its function and effectiveness. Therefore, we used the Yangtze River Delta Region (YRDR) as a case study and conceptualized an integrated framework to evaluate the spatial pattern and mechanisms of NR under the superposition of the COVID-19 pandemiv and major holidays. The results indicated that the topology of a population mobility network ...
Traffic monitoring with infrastructure-based sensors is effective and reliable for improving traf... more Traffic monitoring with infrastructure-based sensors is effective and reliable for improving traffic safety and traffic monitoring on high-volume roads, but not on low-volume roads. Low-volume roads in remote areas lack traffic monitoring sensors and thus traffic incidents are difficult to detect in a timely manner. Hence, this paper focused on low-volume road, and introduced Unmanned Aerial Vehicle (UAV) to detect traffic incident and analyzed its feasibility. Firstly, the research aim and definition of traffic incident were presented. Then, a numerical simulation method of using UAV to detect traffic incident was proposed, and a simulation case study with sensitivity analysis was implemented. Next, a UAV flight experiment was conducted. Finally, the cost-benefit analysis of using UAV to detect incident was given. The simulation results showed: (1) the theoretical UAV incident detection rate of the given scenario was 8.80%; (2) extending incident detection time, conducting UAV shuttling flight can increase incident detection rate significantly; and (3) some factors, such as UAV detection range, UAV flight speed and road incident occurrence rate, had little impact on incident detection result. The experiment and cost-benefit analysis showed that it’s cost efficient to use UAV to detect incident for low-volume road.
Road edges recognition is important for various applications in Intelligent Transport System . Th... more Road edges recognition is important for various applications in Intelligent Transport System . This paper focuses on extracting road edges from an image captured by a Unmanned Aerial Vehicle. Linear feature extraction is an important part of this job which is done by a proposed chain-code based algorithm. This paper brings forward a novel direction encoding scheme (DES) which improves encoding efficiency of digital straight lines and overcome drawbacks of Freeman encoding scheme (FES) successfully. DES also simplifies chain-code based line detecting methods from four stages to three. The new DES chain-code based criteria proposed can extract line segments in O(n) time, and curb errors due to digitalization effectively. A rotation of line (ROL) approach is employed for grouping line segments into much longer ones. Experimental results show that algorithm proposed in this paper works pretty well for road edges extraction
International Conference on Transportation Engineering 2009, 2009
Giving priority to transit vehicles at urban intersections could improve transit operation and sc... more Giving priority to transit vehicles at urban intersections could improve transit operation and schedule reliability and attract ridership, it may also be an effective way to alleviate traffic congestion. This paper reports a new method to compute the cycle length at signalized intersections based on the principle of people oriented transportation systems. This is a departure from the current signal timing mechanism based on the average delay per vehicle, which is naturally in favor of private vehicles. Taking the minimum delay per person as the objective and based on the linear programming planning, the author developed a model calculating the optimal cycle length. Furthermore, the model was calibrated and validated in a case study. The result shows that, comparing with traditional control program, the model not only reduced delay per person but also diminished the delay per car dramatically at the same time. It demonstrated that giving priority to bus not only improve bus services but also improve all traffic at urban intersections.
Transportation Research Record: Journal of the Transportation Research Board, 2001
The use of breakeven analysis as a tool to assess the benefits of intelligent transportation syst... more The use of breakeven analysis as a tool to assess the benefits of intelligent transportation systems (ITS) at the system level in systemwide sketch planning is discussed. The breakeven analysis was developed on the basis of the SCRITS (SCReening for ITS) spreadsheet template and used data from Madison, Wisconsin, as a case study and provided considerable in sight into the magnitude of the potential benefits of different ITS programs. The analysis can help identify critical performance variables in the assessment of ITS benefits. Breakeven analysis coupled with sensitivity analysis can be used to identify and assess ITS projects for deployment in the ITS planning and programming process with limited data. It can be used to screen, prioritize, and select ITS projects among different ITS options. It can also be used to compare ITS projects in different geographic locations on the basis of different traffic data and breakeven points. The method is also useful in the identification of da...
2013 21st International Conference on Geoinformatics, 2013
ABSTRACT This paper analyzes characteristics of population distribution and movements of the city... more ABSTRACT This paper analyzes characteristics of population distribution and movements of the city of Shenzhen in southern China by using mobile phone position data, and visualizes the distribution and movements of population in Shenzhen. Nowadays, positioning information of calling activity records of cell phones is more and more feasible with popularity of cell phones and development of the cell network. The tremendous advantages of positioning data in massive data samples, real-time and coverage guarantee it can be a significant supplement tool to monitor population dynamics. The experimental results display a vivid visual representation of population distribution and their movements through space and time. This paper's analytical method and results can potentially contribute to a better understanding of the surrounding city and further benefits to urban planning and management.
ABSTRACT In recent years, the increasing development of traffic information collection technology... more ABSTRACT In recent years, the increasing development of traffic information collection technology based on floating car data has been recognized, which gives rise to the establishment of real-time traffic information dissemination system in many cities. However, the recent massive construction of urban elevated roads hinders the processing of corresponding GPS data and further extraction of traffic information (e.g., identifying the real travel path), as a result of the frequent transfer of vehicles between ground and elevated road travel. Consequently, an algorithm for identifying the travel road type (i.e., elevated or ground road) of vehicles is designed based on the vehicle traveling features, geometric and topological characteristics of the elevated road network, and a trajectory model proposed in the present study. To be specific, the proposed algorithm can detect the places where a vehicle enters, leaves or crosses under elevated roads. An experiment of 10 sample taxis in Shanghai, China was conducted, and the comparison of our results and results that are obtained from visual interpretation validates the proposed algorithm.
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