Modeling dynamic vehicle age distribution in Beijing

Intelligent transportation systems (ITS) technologies have been used to control vehicle emissions in dynamic traffic networks in which the accurate quantification of vehicle emissions is the key to developing any effective emission control strategies. MOBILE is an emission factor model developed by the U.S. Environmental Protection Agency (EPA) to quantify vehicle emissions, which is also being used in China at present due to the fact that China does not have its own emission factor model. It has been shown in the past research that Vehicle Age Distribution (VAD) is one of important traffic parameters that affect the MOBILE outputs. To use the default VAD in MOBILE to generate emission factors in China will likely result in considerable errors. This paper proposes a survival probability-based dynamic model to calculate and forecast the area-specific VAD by using the total number of registered vehicles and the total number of newly registered vehicles (or the number of scrapped vehicles). To illustrate the effectiveness of the proposed model, the calculation of the light duty vehicle age distribution in Beijing is presented. It is shown that the proposed model has a minimum requirement of data, which can be easily implemented in areas/cities where a complete historical vehicle registration record does not exist.