United States Department of Transportation
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Corporate Contributors:United States. Department of Transportation. Federal Highway Administration. Turner-Fairbank Highway Research Center ; United States. Federal Highway Administration. Office of Infrastructure Research and Development ; United States. Federal Highway Administration. Office of Natural Environment and Planning
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Edition:Final Report; 1978-2001
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Abstract:A user-friendly model for personal computers, "Vehicle/Highway Performance Predictor," was developed to estimate fuel consumption and exhaust emissions related to modes of vehicle operations on highways of various configurations and traffic controls for highway designers and planners and strategists optimizing Intelligent Transportation Systems. This model simulates operations of vehicles by evaluations of the vehicle external loads or propulsive demands, which are determined by longitudinal and lateral accelerations, positive and negative road grades, rolling resistance, and aerodynamic drag for various transmission gears. The computations of fuel consumption and air pollutant emissions are then related to the vehicle maps of fuel consumption and air contaminant emission rates as evaluated from large-roll dynamometer measurements for vehicle operations under various loads, speeds, and transmission gears or as may be estimated based on engine maps, speeds, loads, and vehicle drive-train characteristics. The supportive experimental program for the model development showed the following: 1) Propulsive or external loads imposed by highway features such as curves and grades can be measured and simulated on a large-roll chassis dynamometer and are predictable, but the dynamometer simulation is not needed if the vehicle fuel consumption and air contaminant emission rates vs. total propulsive demand are used to create a vehicle data base; 2) Driveshaft torque measured on an instrumented vehicle showed that, for steady speeds on flat highway, the road load is a quadratic function of speed, a quadratic function of lateral acceleration, and a linear function of positive or negative grades or positive or negative longitudinal accelerations; 3) For one tested vehicle, the energy loss in drive axle and tires was described well as a loss of tractive force expressed as a quadratic function of only the total drive torque or tractive force; and 4) A prototype method was developed to compare rolling resistance of pavement surfaces based on known vehicle speeds, road grades, and total external load indicated by driveshaft torque.
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