Evaluation Of Traffic Emissions At Microscopic Level Based On MOVES

The continuing growth of the automobile ownership has brought up increasingly serious environmental pollution problems. In response, China has developed a series of transportation strategies to reduce vehicle emissions. The ability to accurately quantify traffic emissions is the key to evaluating emission reduction effects of various transportation strategies. A very important problem being faced when using emission models to estimate vehicle emissions is the precise description of traffic conditions. However, existing emission models are extremely inadequate in obtaining and describing traffic conditions.In this context, this study in this thesis is intended to propose a method of obtaining traffic status parameters at the microscopic level based on the new generation emission model, MOVES, developed by the U.S. Environmental Protection Agency (U.S. EPA), and further improve the method of estimating emissions at the microscopic level. The proposed research includes the following:First, the thesis provides a review of vehicle emission models, and compares and analyzes structures, principles, and the development trend of main stream emission models. Based on the accuracy of the emission calculation as well as the comprehensiveness of calculation levels, the MOVES model is selected as the model to be studied. Further, the microscopic level in MOVES is selected as the target level of study from the standpoint of integrating the emission model with dynamic traffic parameters.Second, the thesis conducts a sensitivity analysis of local parameters at the microscopic level in MOVES. It is found that emission calculation results are more sensitive to the parameters of speed and vehicle age.Third, the differences and relationships among the parameters of average speed, driving schedule, and operating mode distribution (VSP distribution) in the process of emission calculations are discussed, and the operating modes on expressways and non-expressways are compared and analyzed. It is found that VSP distributions are more accurate than the other two parameters in describing vehicle operational characteristics.Fourth, the study proposes methods to obtain critical traffic parameters of the average speed, drive schedule, and operating mode distribution in conditions when GPS devices are either available or unavailable, as well as other parameters. On this basis, it analyzes comparatively emission factors calculated based on the operating mode distribution, the average speed, and the real-world second-by-second driving data. It is observed that emission factors calculated based on the operating mode distribution is closer to the real-world data than those based on the average speed, which show an increase of the accuracy by 68%,74%,77%,87% and 43% respectively for fuel consumptions, CO2, NOx, CO, and HC.Finally, the thesis uses the proposed method for obtaining traffic parameters to conduct a case study for the electronic toll strategy. After a comparative analysis, it is found that emission factors of HC, CO, NOx, and CO2 for vehicles passing through the electronic toll collection (ETC) are reduced by 48%,36%,50%, and 47% respectively than passing through the manual toll collection (MTC), which provides good consistency with the real-world data. Consequently, the proposed method of obtaining traffic parameters can be effectively used in the evaluation of traffic emissions at microscopic level.