Validation of temporal and spatial consistency of facility- and speed-specific vehicle-specific power distributions for emission estimation: A case study in Beijing, China

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Vehicle-specific power (VSP) has been found to be highly correlated with vehicle emissions and is used in many studies on emission modeling, e.g., Motor Vehicle Emissions Simulator (MOVES) model. The existing studies develop specific VSP distributions or OpMode distribution in MOVES for different road types and various average speeds to represent the vehicle operating modes on road. The temporal and spatial consistency of the facility- and speed-specific VSP distributions in Beijing was investigated. The VSP distributions in different years and in different areas were developed, based on real-world vehicle activity data. The root mean square error was applied to quantify the difference between the VSP distributions. The maximum differences of the VSP distributions between different years and between different areas were approximately 20% of that between different road types. The analysis of the CO2 emission factor indicated that the temporal and spatial differences of the VSP distributions have no great impact on vehicle emission estimation, with relative error of less than 3%. The database of the specific VSP distributions in the VSP-based emission models can maintain in terms of time. Thus, it is unnecessary to update the database regularly, and it is reliable to use the history vehicle activity data to forecast the emissions in the future.