United States Department of Transportation
i
Development and validation of light-duty vehicle modal emissions and fuel consumption values for traffic models.
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1999-03-01
[PDF-6.11 MB]
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OCLC Number:499082944
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Abstract:A methodology for developing modal vehicle emissions and fuel consumption models has been developed by Oak Ridge National Laboratory (ORNL), sponsored by the Federal Highway Administration. These models, in the form of look-up tables for fuel consumption and emissions as functions of vehicle speed and acceleration, are designed for simulations such as the Federal Highway Administration's TRAF-series of models. These traffic models are used to evaluate the impacts of roadway design on emissions and fuel consumption. Vehicles are tested on-road and on a chassis dynamometer to characterize the entire operating range of each vehicle. Engine parameters are measured on-the-road as functions of vehicle speed and acceleration while driving the cars through their entire operating envelope. Following road testing, the vehicles are driven on the chassis dynamometer while making transient and steady-state emissions and fuel consumption measurements as functions of the same engine parameters. The two data sets are merged numerically to deliver data-based models of fuel consumption and emissions as functions of vehicle speed and acceleration. The data-based models are models only in the sense that numerical methods are used to create a smooth surface using discreet data points; no simulations or assumptions are made in the creation of data-based models. As a validation exercise, the models were used to predict cycle emissions and fuel consumption and the results were compared to certification-type tests on a different population of vehicles. Results of the verification exercise show that the developed models can generally predict cycle emissions and fuel comsuption with error rates comparable to the variability of repeated dynamometer tests.
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