Study On The Influence Of Highway Alignment On Motor Vehicle Emissions

With the rapid development of highway transportation and the sharp increase in the number of motor vehicles,motor vehicle emissions had gradually become one of the main sources of environmental pollution in China,while the characteristics of strong mobility and large dispersion made it more difficult to govern and control than other sources of pollution.Motor vehicle pollution emissions were not only affected by vehicle performance and environmental factors,but also closely related to highway alignment conditions.However,research was still in its infancy which was on the relationship between vehicle pollution emissions and highway alignment.With purpose of motor vehicle pollution reduction in this research,the pollution emission laws of motor vehicles were calculated and output respectively.And the improvement suggestions for improving the geometric design of highways were raised up based on vehicle emission laws.Guide engineering technicians to pay attention to ecological and environmental benefits in the design stage,so as to better achieve green and sustainable development of highway construction and even the transportation industry.This study analyzed and compared the commonly used vehicle simulation and pollution emission models,and determined the coupling ideas of the Car Sim,Truck Sim model and MOVES model with operating conditions as intermediate variables.combined with factors of local vehicle attributes and environmental characteristics,the parameters required of model were processed locally,and a simulation model of motor vehicle pollution emission based on highway alignment was constructed.Meanwhile,the data interaction processing programs CTM and TTM between models were designed and developed.The calculation method of vehicle VSP was refined during the compilation process,therefore the error caused by simplified calculation was reduced and accurate and fast conversion of data between models were realized.The highway is categorized various sections on the basis of the horizontal and vertical geometry alignment index,including straight section,horizontal curve section,longitudinal section and curve-ramp section.The quantitative relationship between vehicle pollution emissions and different linear elements,which provides theoretical guidance for the design of highway alignment to reduce motor vehicle pollution was determined through applying research methods of data fitting and multiple regression analysis.The research results demonstrated that different linear elements had a certain impact on vehicle emissions and the importance of which was the slope i,the radius of the flat curve R and the slope differenceωin turn.The CO emissions of small vehicles and NO_xemissions of large vehicles were more sensitive to the linear changes of highways.As the road alignment became worse,the emission level promoted and the rate of change gradually increased.Combined with the case analysis of the Tianlin-Xilin highway project,a simulation model of motor vehicle pollution emission was constructed based on the horizontal and vertical design data of a certain length of road section to simulate the dynamic change process of the vehicle’s pollution emission with the linear change during the actual highway driving process.Compared with the results of the calculation output and the existing actual vehicle emission data,the reliability of the study was further verified.