Conference Interactive Program
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TRB 90th Annual Meeting (January 23-27, 2011)
Current Environmental Issues in Transportation
Jan 25 2011 9:30AM- 12:00PM
Hilton, International Center
Analysis of U.S. EPA's MOVES Model's Operating Modes and Handling of History Effects (11-0597)
The U.S. Environmental Protection Agency (EPA) has recently released the MOVES (MOtor Vehicle Emission Simulator) model for estimating emissions from mobile sources. The MOVES model was developed over ten years and is one of the most advanced multi-scale emission models. Thus far, MOVES has been internally validated primarily within EPA, comparing model results with independent real-world emission measurements. It is expected that as the model is more widely used by others, model validity will be a topic of increased interest. The MOVES modeling methodology is based on integrating vehicle activity distributions with emission factors that are a function of vehicle specific power and speed. As such, there is no direct accounting for emission history effects. In other words, the emissions predicted are based on the instantaneous measures of vehicle activity and its corresponding vehicle specific power; there is no direct accounting for the past historical operational activity (e.g., 10 to 20 seconds). In this paper, we examine the MOVES model in comparing it with independent emissions measurements with the goal of seeing if the emissions historical effect has a significant impact on predicted emissions. It was found that the history effect does indeed affect emissions. The errors produced by instantaneous estimation without accounting for history effects were observed when directly comparing modeling results with measurement trajectories. A quantitive analysis shows that the higher power OpModes (33, 35, 37, 38, and 40) had the greatest variability due to the history effect for carbon monoxide (CO) and hydrocarbons (HC), in the range of 50-150% and 40-60% respectively for particular vehicle activity events. For lower power OpModes (<30), HC and oxides of nitrogen (NOx) are affected by history effects in the range of 20%-50% for other types of events.
Liu, Huan , Tsinghua University, China
Barth, Matthew J., University of California, Riverside
Transportation Research Board. 500 Fifth St. NW, Washington, D.C. 20001
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