Research On The Impact Of Tram Opening On Traffic Pollution In Songjiang New Town

The development of transport infrastructure is an important driver of economic development and one of the effective ways to mitigate urban traffic air pollution.In order to maximize the role that transport infrastructure can play in relieving the pressure on urban road traffic and reducing vehicle emissions,it is necessary to understand the mechanisms by which transport infrastructure affects traffic pollution.Trams are being built and developed in many new cities to optimize the existing transportation system and form a diversified integrated transportation network.In this paper,typical tram sections are selected in Songjiang New Town.Based on spatial and temporal microscopic data of typical sections before and after the opening of the trams,the localized MOVES model was used to simulate the traffic pollution emissions.The effects of trams opening on traffic and pollution emission characteristics were analyzed and compared.Then,the characteristics of land use,population density,traffic transfers and traffic signals of typical sections were analyzed and compared,and the factors influencing the direction of the effect of trams on traffic and pollution emission characteristics were identified using Spearman’s correlation coefficient.Finally,the impact of the Songjiang New Town trams on traffic pollution is predicted by combining the traffic development plan of Songjiang New Town and the changes of traffic pollution in typical sections.The specific conclusions are as follows:(1)After the opening of the tram,the overall traffic flows of typical sections shows a downward trend.The traffic flow of Line 1,Line 2,and comparison section decreased by 7.8%,23.7%,and 13.3%,respectively.The reduction in traffic flows during the operating hours of the tram on typical sections is smaller than that during the shutdown hours of tram,and the differences between sections are significant.Compared with comparison section,the reduction in traffic flows on Line 1 is smaller,while that on Line2 is greater.In addition,traffic density on Line 1 is the highest,reaching 512 veh/km,indicating more congested traffic,while the traffic flow density on Line 2 is the lowest,at291 veh/km,indicating smoother traffic.(2)After the opening of trams,traffic pollution emission,emission intensity,and total equivalent emission of typical sections generally showed a downward trend.The CO,HC,and NO_xemissions on Line 1 decreased by 6.1%,3.5%,and 3.3%,respectively,while those on Line 2 decreased by 31.4%,29.8%,and 28.6%,respectively.The CO,HC,and NO_x emissions on comparison section decreased by 27.0%,22.0%,and 21.3%,respectively.During the operating hours of trams,compared with comparison section,the reduction in pollutant emissions on Line 2 was greater,while the pollutant emissions on Line 1 showed an upward trend,with the highest increase reaching 15.6%.(3)According to the analysis of changes in traffic flows and pollutant emissions on typical sections after the opening of trams,it can be concluded that the opening of trams has created more travel demands for traffic-busy Line 1,exacerbating traffic pollution emissions,and making the traffic creation effect more significant.For traffic-smooth Line 2,the opening of trams provides an alternative public transportation option,replacing some use of private cars,improving traffic pollution emissions,and making the traffic replacement effect more significant.This conclusion highlights the importance of considering differences in traffic conditions when evaluating the effects of the opening of trams on traffic and pollution.(4)The land use,transportation transfer,and population density along typical tram sections significantly affect the direction of tram’s impact on traffic flows and pollutant emissions,while traffic signals have no significant impact.Among them,population density is positively correlated with changes in traffic flows and pollutant emissions.In terms of land use,the Spearman correlation coefficient between shopping centers and changes in traffic flows,HC,CO,and NO_x emissions is-0.545(p<0.01),-0.455(p<0.01),-0.354(p<0.01),and-0.342(p<0.01),respectively,showing a strong negative correlation.The Spearman correlation coefficients between green space and changes in traffic flows and HC emissions are-0.369(P<0.01)and-0.233(P<0.05),respectively,also showing negative correlation.This indicates that in sections with lower population density and more shopping centers and green spaces,the substitution effect of tram for cars is stronger.In addition,the number of bus routes along sections is positively correlated with changes in traffic flows(r=0.297,p<0.05),indicating that on sections with more bus routes,the decrease in traffic flows is relatively small,indicating that buses on typical sections have not attracted more residents to transfer to trams.(5)Based on the LEAP model,the future phase of energy demand,and pollutant emissions of passenger cars in Songjiang New City were predicted.The results show that with the increase of market penetration rate and fuel economy of electric cars in Songjiang New City,the proportion of electric cars is expected to reach 30.04%by 2030,and energy consumption can be reduced by up to 49.80%,and pollutant emissions will decrease by around 50%.We simulated and verified the existing tram planning scheme in Songjiang New Town,and found that the planning scheme can well realize the traffic substitution role of trams and alleviate the traffic congestion in the new town.However,with the continuous increase in population in Songjiang New City,the operation pressure of light rail transit in densely populated areas such as residential areas is still high.This study explores the direction and influencing factors of the trams opening on the traffic and pollution emissions characteristics of typical sections at the spatial and temporal microscopic level.The impact of the tram’s development on traffic pollution in Songjiang New City is also predicted based on relevant plannings.The links and impacts between transportation infrastructures and traffic pollutions are identified at the micrometric level,providing a reference for the construction of small or medium-scale transportation infrastructure in the developing city.