As a common transportation facility, speed humps can control the speed of vehicles on special road sections to reduce traffic risks. At the same time, they also cause instantaneous traffic emissions. Based on the clas...As a common transportation facility, speed humps can control the speed of vehicles on special road sections to reduce traffic risks. At the same time, they also cause instantaneous traffic emissions. Based on the classic instantaneous traffic emission model and the limited deceleration capacity microscopic traffic flow model with slow-to-start rules, this paper has investigated the impact of speed humps on traffic flow and the instantaneous emissions of vehicle pollutants in a single lane situation. The numerical simulation results have shown that speed humps have significant effects on traffic flow and traffic emissions. In a free-flow region, the increase of speed humps leads to the continuous rise of CO_(2), NO_(X) and PM emissions. Within some density ranges, one finds that these pollutant emissions can evolve into some higher values under some random seeds. Under other random seeds, they can evolve into some lower values. In a wide moving jam region, the emission values of these pollutants sometimes appear as continuous or intermittent phenomenon. Compared to the refined Na Sch model, the present model has lower instantaneous emissions such as CO_(2), NO_(X) and PM and higher volatile organic components(VOC) emissions. Compared to the limited deceleration capacity model without slow-to-start rules, the present model also has lower instantaneous emissions such as CO_(2), NO_(X) and PM and higher VOC emissions in a wide moving jam region. These results can also be confirmed or explained by the statistical values of vehicle velocity and acceleration.展开更多
This paper introduces an innovative approach to the synchronized demand-capacity balance with special focus on sector capacity uncertainty within a centrally controlled collaborative air traffic flow management(ATFM)f...This paper introduces an innovative approach to the synchronized demand-capacity balance with special focus on sector capacity uncertainty within a centrally controlled collaborative air traffic flow management(ATFM)framework.Further with previous study,the uncertainty in capacity is considered as a non-negligible issue regarding multiple reasons,like the impact of weather,the strike of air traffic controllers(ATCOs),the military use of airspace and the spatiotemporal distribution of nonscheduled flights,etc.These recessive factors affect the outcome of traffic flow optimization.In this research,the focus is placed on the impact of sector capacity uncertainty on demand and capacity balancing(DCB)optimization and ATFM,and multiple options,such as delay assignment and rerouting,are intended for regulating the traffic flow.A scenario optimization method for sector capacity in the presence of uncertainties is used to find the approximately optimal solution.The results show that the proposed approach can achieve better demand and capacity balancing and determine perfect integer solutions to ATFM problems,solving large-scale instances(24 h on seven capacity scenarios,with 6255 flights and 8949 trajectories)in 5-15 min.To the best of our knowledge,our experiment is the first to tackle large-scale instances of stochastic ATFM problems within the collaborative ATFM framework.展开更多
Based on the gap acceptance theory, the mixed traffic flow composed of r representative types of vehicles 1, 2,…, r vehicles is analyzed with probability theory. Capacity model of the minor mixed traffic flow ...Based on the gap acceptance theory, the mixed traffic flow composed of r representative types of vehicles 1, 2,…, r vehicles is analyzed with probability theory. Capacity model of the minor mixed traffic flow crossing m major lanes with M3 distributed headway on the unsignalized intersection is set up, and it is an extension of capacity model for one minor lane vehicle type crossing one major lane traffic flow.展开更多
Delay analysis method is adopted to study the service capacity of a widened intersection. Traffic simulation software VISSIM is used for microscopic simulation of a widened intersection so as to obtain a delay curve. ...Delay analysis method is adopted to study the service capacity of a widened intersection. Traffic simulation software VISSIM is used for microscopic simulation of a widened intersection so as to obtain a delay curve. The delay-volume model of a widened intersection is established based on traffic simulation. The suggested value of basic service capacity of the widened left-turn lane is given along with how to determine correction factors and practical service capacity.展开更多
In the traffic equilibrium problem, we introduce capacity constraints of arcs, extend Beckmann’s formula to include these constraints, and give an algorithm for traffic equilibrium flows with capacity constraints on ...In the traffic equilibrium problem, we introduce capacity constraints of arcs, extend Beckmann’s formula to include these constraints, and give an algorithm for traffic equilibrium flows with capacity constraints on arcs. Using an example, we illustrate the application of the algorithm and show that Beckmann’s formula is a sufficient condition only, not a necessary condition, for traffic equilibrium with capacity constraints of arcs.展开更多
Highway capacity is defined as maximum volume of traffic flow through the particular highway section under given traffic conditions, road conditions and so on. Highway construction and management is judged by capacity...Highway capacity is defined as maximum volume of traffic flow through the particular highway section under given traffic conditions, road conditions and so on. Highway construction and management is judged by capacity standard. The reasonable scale and time of highway construction, rational network structure and optimal management mode of highway network can be determined by analyzing the fitness between capacity and traffic volume. All over the world, highway capacity is studied to different extent in different country. Based on the gap acceptance theory, the mixed traffic flow composed of two representative vehicle types heavy and light vehicles is analyzed with probability theory. Capacity model of the minor mixed traffic flows crossing m major lanes, on which the traffic flows fix in with M3 distributed headway, on the unsignalized intersection is set up, and it is an extension of minor lane capacity theory for one vehicle-type and one major-lane traffic flow.展开更多
Roundabout is a channelized intersection where traffic moves around a central island,clockwise for leftside driving and anti-clockwise for right-side driving.Efficiently designed roundabouts can handle traffic very sm...Roundabout is a channelized intersection where traffic moves around a central island,clockwise for leftside driving and anti-clockwise for right-side driving.Efficiently designed roundabouts can handle traffic very smoothly without causing any delay.The capacity of roundabouts used to be calculated by the weaving theory in India.However,calculation of the entry capacity in the recent literature is based on critical gaps and follow-up times,and the Highway Capacity Manual of US(HCM2010)provides an equation to estimate the entry capacity of a roundabout by using the flow in passenger car unit per hour(PCU/h),critical gaps and follow-up times at the entry section.In order to examine whether the HCM equation applies to Indian traffic condition or not,we collected data from five roundabouts in India in this study.Relevant data were extracted/estimated to calibrate parameters of the HCM equation.The PCU for a vehicle was estimated on the basis of lagging headway and width of the vehicle,and the critical gap value for a vehicle was estimated by minimizing the sum of absolute difference in a gap with respect to the highest rejected and accepted gaps.Results show that the critical gap values obtained under heterogeneous traffic conditions are much lower than those given in the literature for homogeneous traffic conditions.In addition,the modified HCM equation based on the critical gap values was verified using the field data taken during the formation of a continuous and stable queue at the entry of a roundabout.It was found that a multiplicative adjustment factor needs to be calculated for different sizes of roundabouts to ensure the adjusted HCM equation represents well the traffic condition prevailing in developing countries like India.A test conducted at another roundabout validated that the entry capacity estimated from the calibrated and adjusted HCM model was consistent with the field entry capacity,and the calibrated and adjusted HCM model could predict the entry capacity of an approach to a roundabout quite accurately.展开更多
The capacity is impacted badly by pedestrians' violation behavior at signal intersections. In order to quantify the impact,the time-headway and the vehicular speed from start-up to reach the stable saturation flow...The capacity is impacted badly by pedestrians' violation behavior at signal intersections. In order to quantify the impact,the time-headway and the vehicular speed from start-up to reach the stable saturation flow with and without pedestrian traffic are used as the direct measurements. Using the statistical analysis,the timeheadway of saturation flow is mainly affected by the position of pedestrians and the degree of pedestrians 'influence is classified into four levels. Then the speed-time profile for the vehicular acceleration at each level is fitted by Curve Fitting Software. Based on the effect to the time-headway and acceleration time,the model of capacity influenced by pedestrians is established and the influence is quantified, which enriches the fundamental theory of traffic engineering. The result shows that the vehicular capacity can be decreased by 14%at the worst case( level I). The conclusions obtained in this paper are valuable for better management of the signal intersection.展开更多
In this paper, the concept of the Shortest-Route Traffic Matrix(SRTM) was first presented, and the generalized formula for computing ring capacity requirement in use of SRTM is given. Then, a new capacity design algor...In this paper, the concept of the Shortest-Route Traffic Matrix(SRTM) was first presented, and the generalized formula for computing ring capacity requirement in use of SRTM is given. Then, a new capacity design algorithm which is based on SRTM was presented for Synchronous Digital Hierarchical(SDH) Bi-directional Self-Healing Ring (BSHR). The algorithm simulation results demonstrate that this algorithm is very efficient for SDH BSHR capacity design and can make less project investment and make high utilization of lines and equipment. By means of the algorithm in this paper, capacity optimization assignment for SDH Hierarchical Self-Healing Ring (HSHR) and for ATM Virtual Path (VP)-based Self-Healing Ring (SHR) is also discussed.展开更多
To determinate the expressway capacity near a bus bay stop with an access, capacity models on the expressway near a bus stop with an access were developed on the basis of gap acceptance theory and queuing theory. Depe...To determinate the expressway capacity near a bus bay stop with an access, capacity models on the expressway near a bus stop with an access were developed on the basis of gap acceptance theory and queuing theory. Depending on a bus stop position to an entrance or an exit ramp, the capacity models were developed for four cases. Bus bay stops with overflow and bus bay stops without overflow were considered. A comparison of simulation experiment and model calculation was carried out. Results show that the suggested models have high accuracy and reliability, at bus arrival rate below 60 vehicles per hour(veh/h) or vehicle volumes at the entrance and the exit below 200 passenger cars units per hour(pcu/h), and there are no significant difference in the capacities for four cases. When bus arrival rate is above 240 veh/h, the capacities of all four cases will decline rapidly. With berth number increasing, the increasing of the capacities is no obvious for four cases. As the bus arrival rate and vehicle volumes at the entrance and the exit increase, bus stops located downstream of an entrance and upstream of an exit have a remarkably effect on the capacities. The latter case is much heavier than the former. Those results can be used to traffic design and optimization on urban expressway near a bus stop with an access.展开更多
In order to reduce the traffic pressure of urban arterial road with the rational utilization of the branch road,the vehicle meeting behavior on the branch road without divided lane was described,and the cellular autom...In order to reduce the traffic pressure of urban arterial road with the rational utilization of the branch road,the vehicle meeting behavior on the branch road without divided lane was described,and the cellular automation (CA) model was put forward by introducing meeting behavior to reflect the relation between safe meeting speed and road width.The numerical simulation results depict several relation curves between road section capacity,speed and road width under different directional distributions of traffic flow,as well as the curves between the major and minor direction saturation flow,speed and road width.These relation characteristics indicate that except the one-way road section capacity and speed remaining unchanged,other road section capacities and speeds under different directional distributions increase with the increase of road width.On narrow road,the two-way traffic capacity and speed are less than those of one-way traffic;on wide road,the two-way traffic capacity doubles that of one-way traffic,but their speeds are almost the same.As the directional distribution moves to an even distribution of 50/50,the major direction saturation flows and speeds as well as the minor direction speeds tend to decease,while the minor direction saturation flow tends to increase.展开更多
To investigate bicyclists＇ behavior at unsignalized intersections with mixed traffic flow, a bicycle capacity model of borrowed-priority merge was developed by the addition-conflict-flow procedure. Based on the actua...To investigate bicyclists＇ behavior at unsignalized intersections with mixed traffic flow, a bicycle capacity model of borrowed-priority merge was developed by the addition-conflict-flow procedure. Based on the actual traffic situation, the concept of borrowed priority, in which the majorroad bicycles borrow the priority of major-road cars to enter the intersections when consecutive headway for major-steam cars is lower than the critical gap for minor-road cars, was addressed. Bicycle capacity at a typical unsignalized intersection is derived by the addition-conflict-flow procedure. The proposes model was validated by the empirical investigation. Numerical results show that bicycle capacity at an intersection is the function of major-road and minor-road car streams. Bicycle capacity increases with increasing major-road cars but decreases with increasing minorroad cars.展开更多
A method for evaluating instantaneous sector capacity based on the workload of air traffic controller(ATC)is developed.The basic characteristics of the assessed sector is described and a model to correlate the workloa...A method for evaluating instantaneous sector capacity based on the workload of air traffic controller(ATC)is developed.The basic characteristics of the assessed sector is described and a model to correlate the workload with the instantaneous sector capacity is developed using workload data.The correlation between the regional sector/approach sector capacity and the traffic flow organization is analyzed.Experimental results show that the instantaneous sector capacity assessment is reasonable and the instantaneous capacity is strongly correlated with the spatial and temporal distributions of the traffic flow and the sector operation mode.These results can provide an important reference for sector operation safety,capacity prediction,air traffic management,and airspace design.展开更多
The priority of the EU transport policy in railway sector is to open up the railway market. The objective is to provide railway undertakings with access to the railway network on equal terms. The main problem is deter...The priority of the EU transport policy in railway sector is to open up the railway market. The objective is to provide railway undertakings with access to the railway network on equal terms. The main problem is determining the infrastructure capacity. A variety of methodologies are used across Europe for the capacity estimation of railway infrastructure. This diversity has forced railway infrastructure managers to seek a new, common methodology. The UIC methodology is an easy way to calculate the capacity consumption. However, there the possibility to expound this methodology in different ways, which can result in different capacity consumptions. There isan advantage to improve this methodology and to set a clear and unified method of occupation time estimation. The fundamental improvement to UIC methodology is the definition of the occupation time by the trains. This paper gives a description of Slovak and UIC methodologies as a basis for a newly developed approach. The new way of estimation of the capacity consumption （occupation time） is based on a graphic approach. The new methodology concerns the estimation of the infrastructure occupation time and is a conceptual framework developed by the authors for an easier evaluation of occupation time in train traffic diagrams. The new methodology makes the UIC methodology more usable and enables more exact results to be obtained from infrastructure capacity examination.展开更多
In these days the traffic is expanding quickly and the activity conditions on Indian roads are exceedingly heterogeneous in nature because of variety of vehicles with various static and dynamic qualities.Due to unrest...In these days the traffic is expanding quickly and the activity conditions on Indian roads are exceedingly heterogeneous in nature because of variety of vehicles with various static and dynamic qualities.Due to unrestricted movements all fast and slow moving vehicles without any separation,the roads will face severe congestion and lower speeds.The greater part of national and state highways in India are two lane undivided roadway.These two lane highways achieve its greatest limit soon and require consistent up gradation to do this we need to estimate capacity of selected roads.In this present paper,attempts have been made to collect traffic volume for whole 7 days at national highways such as NH-206&NH-209.Also tried to compute PCU values at selected stretches on highways by using those values attempts has been made to estimate capacity and to compare those values with the regression equation values.Finally from the present study we got ADT at different section on highways,calculated PCU values as per Chandra’s method at various sections on highways and got marginal difference with the values recommended by IRC.It is found that with the increase in lane width,speed and radius substantially caused increased in PCU value.Also we developed linear regression equations to estimate capacity and compared those values with the values as we got using Chandra’s method.In most of the cases the error is observed to be less than 3%.The percentage error is in the range between 0.02 and 2.41 which is very marginal.Finally from the study it has been observed that increase in lane width and radius at curves obviously increases the capacity their by increases both comfort and safety of the road users.展开更多
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
基金funded by the National Natural Science Foundation of China (Grant No. 11875031)the key research projects of Natural Science of Anhui Provincial Colleges and Universities (Grant No. 2022AH050252)。
文摘As a common transportation facility, speed humps can control the speed of vehicles on special road sections to reduce traffic risks. At the same time, they also cause instantaneous traffic emissions. Based on the classic instantaneous traffic emission model and the limited deceleration capacity microscopic traffic flow model with slow-to-start rules, this paper has investigated the impact of speed humps on traffic flow and the instantaneous emissions of vehicle pollutants in a single lane situation. The numerical simulation results have shown that speed humps have significant effects on traffic flow and traffic emissions. In a free-flow region, the increase of speed humps leads to the continuous rise of CO_(2), NO_(X) and PM emissions. Within some density ranges, one finds that these pollutant emissions can evolve into some higher values under some random seeds. Under other random seeds, they can evolve into some lower values. In a wide moving jam region, the emission values of these pollutants sometimes appear as continuous or intermittent phenomenon. Compared to the refined Na Sch model, the present model has lower instantaneous emissions such as CO_(2), NO_(X) and PM and higher volatile organic components(VOC) emissions. Compared to the limited deceleration capacity model without slow-to-start rules, the present model also has lower instantaneous emissions such as CO_(2), NO_(X) and PM and higher VOC emissions in a wide moving jam region. These results can also be confirmed or explained by the statistical values of vehicle velocity and acceleration.
文摘This paper introduces an innovative approach to the synchronized demand-capacity balance with special focus on sector capacity uncertainty within a centrally controlled collaborative air traffic flow management(ATFM)framework.Further with previous study,the uncertainty in capacity is considered as a non-negligible issue regarding multiple reasons,like the impact of weather,the strike of air traffic controllers(ATCOs),the military use of airspace and the spatiotemporal distribution of nonscheduled flights,etc.These recessive factors affect the outcome of traffic flow optimization.In this research,the focus is placed on the impact of sector capacity uncertainty on demand and capacity balancing(DCB)optimization and ATFM,and multiple options,such as delay assignment and rerouting,are intended for regulating the traffic flow.A scenario optimization method for sector capacity in the presence of uncertainties is used to find the approximately optimal solution.The results show that the proposed approach can achieve better demand and capacity balancing and determine perfect integer solutions to ATFM problems,solving large-scale instances(24 h on seven capacity scenarios,with 6255 flights and 8949 trajectories)in 5-15 min.To the best of our knowledge,our experiment is the first to tackle large-scale instances of stochastic ATFM problems within the collaborative ATFM framework.
文摘Based on the gap acceptance theory, the mixed traffic flow composed of r representative types of vehicles 1, 2,…, r vehicles is analyzed with probability theory. Capacity model of the minor mixed traffic flow crossing m major lanes with M3 distributed headway on the unsignalized intersection is set up, and it is an extension of capacity model for one minor lane vehicle type crossing one major lane traffic flow.
文摘Delay analysis method is adopted to study the service capacity of a widened intersection. Traffic simulation software VISSIM is used for microscopic simulation of a widened intersection so as to obtain a delay curve. The delay-volume model of a widened intersection is established based on traffic simulation. The suggested value of basic service capacity of the widened left-turn lane is given along with how to determine correction factors and practical service capacity.
文摘In the traffic equilibrium problem, we introduce capacity constraints of arcs, extend Beckmann’s formula to include these constraints, and give an algorithm for traffic equilibrium flows with capacity constraints on arcs. Using an example, we illustrate the application of the algorithm and show that Beckmann’s formula is a sufficient condition only, not a necessary condition, for traffic equilibrium with capacity constraints of arcs.
基金Supported by the National Natural Science Foundation of China（50478071）
文摘Highway capacity is defined as maximum volume of traffic flow through the particular highway section under given traffic conditions, road conditions and so on. Highway construction and management is judged by capacity standard. The reasonable scale and time of highway construction, rational network structure and optimal management mode of highway network can be determined by analyzing the fitness between capacity and traffic volume. All over the world, highway capacity is studied to different extent in different country. Based on the gap acceptance theory, the mixed traffic flow composed of two representative vehicle types heavy and light vehicles is analyzed with probability theory. Capacity model of the minor mixed traffic flows crossing m major lanes, on which the traffic flows fix in with M3 distributed headway, on the unsignalized intersection is set up, and it is an extension of minor lane capacity theory for one vehicle-type and one major-lane traffic flow.
文摘Roundabout is a channelized intersection where traffic moves around a central island,clockwise for leftside driving and anti-clockwise for right-side driving.Efficiently designed roundabouts can handle traffic very smoothly without causing any delay.The capacity of roundabouts used to be calculated by the weaving theory in India.However,calculation of the entry capacity in the recent literature is based on critical gaps and follow-up times,and the Highway Capacity Manual of US(HCM2010)provides an equation to estimate the entry capacity of a roundabout by using the flow in passenger car unit per hour(PCU/h),critical gaps and follow-up times at the entry section.In order to examine whether the HCM equation applies to Indian traffic condition or not,we collected data from five roundabouts in India in this study.Relevant data were extracted/estimated to calibrate parameters of the HCM equation.The PCU for a vehicle was estimated on the basis of lagging headway and width of the vehicle,and the critical gap value for a vehicle was estimated by minimizing the sum of absolute difference in a gap with respect to the highest rejected and accepted gaps.Results show that the critical gap values obtained under heterogeneous traffic conditions are much lower than those given in the literature for homogeneous traffic conditions.In addition,the modified HCM equation based on the critical gap values was verified using the field data taken during the formation of a continuous and stable queue at the entry of a roundabout.It was found that a multiplicative adjustment factor needs to be calculated for different sizes of roundabouts to ensure the adjusted HCM equation represents well the traffic condition prevailing in developing countries like India.A test conducted at another roundabout validated that the entry capacity estimated from the calibrated and adjusted HCM model was consistent with the field entry capacity,and the calibrated and adjusted HCM model could predict the entry capacity of an approach to a roundabout quite accurately.
基金Sponsored by the National Basic Research Program of China(973 Program)(Grant No.2012CB723303)
文摘The capacity is impacted badly by pedestrians' violation behavior at signal intersections. In order to quantify the impact,the time-headway and the vehicular speed from start-up to reach the stable saturation flow with and without pedestrian traffic are used as the direct measurements. Using the statistical analysis,the timeheadway of saturation flow is mainly affected by the position of pedestrians and the degree of pedestrians 'influence is classified into four levels. Then the speed-time profile for the vehicular acceleration at each level is fitted by Curve Fitting Software. Based on the effect to the time-headway and acceleration time,the model of capacity influenced by pedestrians is established and the influence is quantified, which enriches the fundamental theory of traffic engineering. The result shows that the vehicular capacity can be decreased by 14%at the worst case( level I). The conclusions obtained in this paper are valuable for better management of the signal intersection.
基金Supported by Key Project for the Ninth Five-Years Programming of Ministry of Posts and Telecommunications of China
文摘In this paper, the concept of the Shortest-Route Traffic Matrix(SRTM) was first presented, and the generalized formula for computing ring capacity requirement in use of SRTM is given. Then, a new capacity design algorithm which is based on SRTM was presented for Synchronous Digital Hierarchical(SDH) Bi-directional Self-Healing Ring (BSHR). The algorithm simulation results demonstrate that this algorithm is very efficient for SDH BSHR capacity design and can make less project investment and make high utilization of lines and equipment. By means of the algorithm in this paper, capacity optimization assignment for SDH Hierarchical Self-Healing Ring (HSHR) and for ATM Virtual Path (VP)-based Self-Healing Ring (SHR) is also discussed.
基金Project(2012CB723303)supported by National Basic Research Program of China
文摘To determinate the expressway capacity near a bus bay stop with an access, capacity models on the expressway near a bus stop with an access were developed on the basis of gap acceptance theory and queuing theory. Depending on a bus stop position to an entrance or an exit ramp, the capacity models were developed for four cases. Bus bay stops with overflow and bus bay stops without overflow were considered. A comparison of simulation experiment and model calculation was carried out. Results show that the suggested models have high accuracy and reliability, at bus arrival rate below 60 vehicles per hour(veh/h) or vehicle volumes at the entrance and the exit below 200 passenger cars units per hour(pcu/h), and there are no significant difference in the capacities for four cases. When bus arrival rate is above 240 veh/h, the capacities of all four cases will decline rapidly. With berth number increasing, the increasing of the capacities is no obvious for four cases. As the bus arrival rate and vehicle volumes at the entrance and the exit increase, bus stops located downstream of an entrance and upstream of an exit have a remarkably effect on the capacities. The latter case is much heavier than the former. Those results can be used to traffic design and optimization on urban expressway near a bus stop with an access.
基金Project(71171200) supported by the National Natural Science Foundation of China
文摘In order to reduce the traffic pressure of urban arterial road with the rational utilization of the branch road,the vehicle meeting behavior on the branch road without divided lane was described,and the cellular automation (CA) model was put forward by introducing meeting behavior to reflect the relation between safe meeting speed and road width.The numerical simulation results depict several relation curves between road section capacity,speed and road width under different directional distributions of traffic flow,as well as the curves between the major and minor direction saturation flow,speed and road width.These relation characteristics indicate that except the one-way road section capacity and speed remaining unchanged,other road section capacities and speeds under different directional distributions increase with the increase of road width.On narrow road,the two-way traffic capacity and speed are less than those of one-way traffic;on wide road,the two-way traffic capacity doubles that of one-way traffic,but their speeds are almost the same.As the directional distribution moves to an even distribution of 50/50,the major direction saturation flows and speeds as well as the minor direction speeds tend to decease,while the minor direction saturation flow tends to increase.
基金Supported by the National Basic Research Program of China (2012CB725400)the National Natural Science Foundation of China(70901005+2 种基金7107101671131001)Fundamental Research Funds for the Central Universities(2011JBM055)
文摘To investigate bicyclists＇ behavior at unsignalized intersections with mixed traffic flow, a bicycle capacity model of borrowed-priority merge was developed by the addition-conflict-flow procedure. Based on the actual traffic situation, the concept of borrowed priority, in which the majorroad bicycles borrow the priority of major-road cars to enter the intersections when consecutive headway for major-steam cars is lower than the critical gap for minor-road cars, was addressed. Bicycle capacity at a typical unsignalized intersection is derived by the addition-conflict-flow procedure. The proposes model was validated by the empirical investigation. Numerical results show that bicycle capacity at an intersection is the function of major-road and minor-road car streams. Bicycle capacity increases with increasing major-road cars but decreases with increasing minorroad cars.
基金supported by the National Key Technology Research and Development Program of the Ministry of Science and Technology of China(No.2011BAH24B08)
文摘A method for evaluating instantaneous sector capacity based on the workload of air traffic controller(ATC)is developed.The basic characteristics of the assessed sector is described and a model to correlate the workload with the instantaneous sector capacity is developed using workload data.The correlation between the regional sector/approach sector capacity and the traffic flow organization is analyzed.Experimental results show that the instantaneous sector capacity assessment is reasonable and the instantaneous capacity is strongly correlated with the spatial and temporal distributions of the traffic flow and the sector operation mode.These results can provide an important reference for sector operation safety,capacity prediction,air traffic management,and airspace design.
文摘The priority of the EU transport policy in railway sector is to open up the railway market. The objective is to provide railway undertakings with access to the railway network on equal terms. The main problem is determining the infrastructure capacity. A variety of methodologies are used across Europe for the capacity estimation of railway infrastructure. This diversity has forced railway infrastructure managers to seek a new, common methodology. The UIC methodology is an easy way to calculate the capacity consumption. However, there the possibility to expound this methodology in different ways, which can result in different capacity consumptions. There isan advantage to improve this methodology and to set a clear and unified method of occupation time estimation. The fundamental improvement to UIC methodology is the definition of the occupation time by the trains. This paper gives a description of Slovak and UIC methodologies as a basis for a newly developed approach. The new way of estimation of the capacity consumption （occupation time） is based on a graphic approach. The new methodology concerns the estimation of the infrastructure occupation time and is a conceptual framework developed by the authors for an easier evaluation of occupation time in train traffic diagrams. The new methodology makes the UIC methodology more usable and enables more exact results to be obtained from infrastructure capacity examination.
文摘In these days the traffic is expanding quickly and the activity conditions on Indian roads are exceedingly heterogeneous in nature because of variety of vehicles with various static and dynamic qualities.Due to unrestricted movements all fast and slow moving vehicles without any separation,the roads will face severe congestion and lower speeds.The greater part of national and state highways in India are two lane undivided roadway.These two lane highways achieve its greatest limit soon and require consistent up gradation to do this we need to estimate capacity of selected roads.In this present paper,attempts have been made to collect traffic volume for whole 7 days at national highways such as NH-206&NH-209.Also tried to compute PCU values at selected stretches on highways by using those values attempts has been made to estimate capacity and to compare those values with the regression equation values.Finally from the present study we got ADT at different section on highways,calculated PCU values as per Chandra’s method at various sections on highways and got marginal difference with the values recommended by IRC.It is found that with the increase in lane width,speed and radius substantially caused increased in PCU value.Also we developed linear regression equations to estimate capacity and compared those values with the values as we got using Chandra’s method.In most of the cases the error is observed to be less than 3%.The percentage error is in the range between 0.02 and 2.41 which is very marginal.Finally from the study it has been observed that increase in lane width and radius at curves obviously increases the capacity their by increases both comfort and safety of the road users.
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.
