title: Vehicle-specific emissions modeling based upon on-road measurements.
abstract: Vehicle-specific microscale fuel use and emissions rate models are developed based upon real-world hot-stabilized tailpipe measurements made using a portable emissions measurement system. Consecutive averaging periods of one to three multiples of the response time are used to compare two semiempirical physically based modeling schemes. One scheme is based on internally observable variables (IOVs), such as engine speed and manifold absolute pressure, while the other is based on externally observable variables (EOVs), such as speed, acceleration, and road grade. For NO, HC, and CO emission rates, the average R(2) ranged from 0.41 to 0.66 for the former and from 0.17 to 0.30 for the latter. The EOV models have R(2) for CO(2) of 0.43 to 0.79 versus 0.99 for the IOV models. The models are sensitive to episodic events in driving cycles such as high acceleration. Intervehicle and fleet average modeling approaches are compared; the former account for microscale variations that might be useful for some types of assessments. EOV-based models have practical value for traffic management or simulation applications since IOVs usually are not available or not used for emission estimation.
authors.affiliation: Department of Civil, Construction and Environmental Engineering, North Carolina State University, Raleigh, North Carolina 27695-7908, USA. frey@ncsu.edu
authors.forename: H Christopher
authors.initials: HC
authors.lastname: Frey
authors.forename: Kaishan
authors.initials: K
authors.lastname: Zhang
authors.forename: Nagui M
authors.initials: NM
authors.lastname: Rouphail
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D001334:Automobile Driving; D001336:Automobiles; D003198:Computer Simulation; D003627:Data Interpretation, Statistical; D004784:Environmental Monitoring / Q000379:methods*; D052638:Particulate Matter; D011312:Pressure; D012044:Regression Analysis; D014186:Transportation; D001335:Vehicle Emissions
chemical_list: D000393:Air Pollutants; D052638:Particulate Matter; D001335:Vehicle Emissions