Effects of High Emitter Vehicles on the On-Road Vehicle Emission Modeling
Lei Yu, Texas Southern University, October 2000, 114 pp. (467600-1)
The development of advanced infrared remote emission sensing technology brings us a cost-effective and convenient instrument for collecting on-road vehicle exhaust emissions. A research project sponsored by Texas Department of Transportation (TxDOT 0-1485) collected 5000+ on-road emission and modal traffic data using a Remote Emission Sensor (RES) in Houston, and established a series of modal emission models for estimating on-road vehicle emissions. One of the major findings in the TxDOT 0-1485 project was that High Emitter Vehicles (HEV) were included in the collected on-road emission data, which were not significant in quantity, but might pose considerable effects on the quality of the emission models. This research intends to examine the effects of high emitter vehicles on the emission modeling. The research attempts to establish a series of emission regression equations based on different cutting percentages of HEV data. This emission modeling process is based on the notion that the resulting emission models will eventually be modified by incorporating a correction factor to represent the real-world on-road vehicle emissions. The developed emission regression equations are evaluated to determine how the cutting percentages affect the quality of emission models. They are also compared with MOBILE and EMFAC to find out if the emission factor models have effectively captured the effects of high emitter vehicles.
It is found that high emitter vehicles do have significant effects on the emission models. Removing the small portion of HEV data will considerably improve the quality of the emission models. Further, it is found that both MOBILE and EMFAC considerably underestimate the on-road emissions, and therefore these models have not adequately considered the effects of high emitter vehicles in the emission estimation.
Keywords: RES, MOBILE, Emission Estimation, Air Quality, Modal Activity, Traffic Simulation, Traffic Modeling
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