In this paper,the concept of environmental capacity is developed to identify a convenient maximum traffic volume which will not reduce the life quality of residents.The presented method investigates the idea of traffi...In this paper,the concept of environmental capacity is developed to identify a convenient maximum traffic volume which will not reduce the life quality of residents.The presented method investigates the idea of traffic capacity under environmental constraints by calculating the maximum number of vehicles allowed on roads based on acceptable levels of air and noise pollutants.In this study,the permissible noise pollution level and permissible levels of CO and NOxpollution are considered for determining environmental capacity.Results show the significant difference between environmental capacity and functional traffic capacity,introduced by the highway capacity manual(HCM)as a conventional method for estimating functional capacity.Thus,maximum allowed pollution is considered a constraint on a vehicle flow rate,which shows the proper traffic flow for selected streets in Tehran,Iran’s capital.The paper concludes that traffic capacity under noise and air pollution constraints is much less(approximately one-fourth and one-eighth for noise and air pollution respectively)than the current highway capacity estimated using HCM guidelines.Therefore,to save the cities like Tehran from noise and air pollution,traffic flows should be limited to the level of environmental capacity by implementing some travel demand management(TDM)policies like road pricing.展开更多
Travel time and its predictability level are important factors influencing travel behavior and the role of traffic congestion as an important factor in the unreliability of travel time is undeniable.Traffic congestion...Travel time and its predictability level are important factors influencing travel behavior and the role of traffic congestion as an important factor in the unreliability of travel time is undeniable.Traffic congestion is divided into two categories:Recurring and Nonrecurring.In this paper,the effect of recurring congestion,defined as the ratio of the traffic speed over one hour to the free flow speed,will be investigated on the reliability of travel time in terms of the planning time index(PTI)on a 1.467-mile segment along the IS-64 freeway in Chesapeake,Virginia.To do so,two methods have been analyzed in this study:the grey models(GM)and the random forest regression(RFR).By using mean absolute percentage error(MAPE)as a criterion to judge,RFR could show a better and more satisfying performance in predicting PTI values when congestion changes.In the following,to make prediction results of RFR more understanding and easier to use,bagging and bootstrapping are used to improve the model results and more accurately predict the PTI.Then,the outputs were drawn using scatter plots for both peaks separately.Analyzing graphs has shown that for congestion values in the range of 1 to 0.9,PTI is reliable in both peaks.When congestion starts to decrease from 0.9 and reaches 0.7 or 0.75,depending on peak type,PTI is moving in the unreliable area,but it isn’t extreme.Finally,when the congestion value becomes smaller,the rate of change in PTI in both peaks increases.展开更多
文摘In this paper,the concept of environmental capacity is developed to identify a convenient maximum traffic volume which will not reduce the life quality of residents.The presented method investigates the idea of traffic capacity under environmental constraints by calculating the maximum number of vehicles allowed on roads based on acceptable levels of air and noise pollutants.In this study,the permissible noise pollution level and permissible levels of CO and NOxpollution are considered for determining environmental capacity.Results show the significant difference between environmental capacity and functional traffic capacity,introduced by the highway capacity manual(HCM)as a conventional method for estimating functional capacity.Thus,maximum allowed pollution is considered a constraint on a vehicle flow rate,which shows the proper traffic flow for selected streets in Tehran,Iran’s capital.The paper concludes that traffic capacity under noise and air pollution constraints is much less(approximately one-fourth and one-eighth for noise and air pollution respectively)than the current highway capacity estimated using HCM guidelines.Therefore,to save the cities like Tehran from noise and air pollution,traffic flows should be limited to the level of environmental capacity by implementing some travel demand management(TDM)policies like road pricing.
文摘Travel time and its predictability level are important factors influencing travel behavior and the role of traffic congestion as an important factor in the unreliability of travel time is undeniable.Traffic congestion is divided into two categories:Recurring and Nonrecurring.In this paper,the effect of recurring congestion,defined as the ratio of the traffic speed over one hour to the free flow speed,will be investigated on the reliability of travel time in terms of the planning time index(PTI)on a 1.467-mile segment along the IS-64 freeway in Chesapeake,Virginia.To do so,two methods have been analyzed in this study:the grey models(GM)and the random forest regression(RFR).By using mean absolute percentage error(MAPE)as a criterion to judge,RFR could show a better and more satisfying performance in predicting PTI values when congestion changes.In the following,to make prediction results of RFR more understanding and easier to use,bagging and bootstrapping are used to improve the model results and more accurately predict the PTI.Then,the outputs were drawn using scatter plots for both peaks separately.Analyzing graphs has shown that for congestion values in the range of 1 to 0.9,PTI is reliable in both peaks.When congestion starts to decrease from 0.9 and reaches 0.7 or 0.75,depending on peak type,PTI is moving in the unreliable area,but it isn’t extreme.Finally,when the congestion value becomes smaller,the rate of change in PTI in both peaks increases.
