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This recommended practice provides minimum requirements for testing components or systems of the type which can be switched from one truck to another with relative ease; i.e., aerodynamic devices, clutch fans, radial tires, and the like. The test utilizes in-service fleet vehicles, operated over representative routes. The relative fuel effectiveness of the component or system under test is determined as a percentage improvement factor. This factor is calculated using the relative fuel usage of like vehicles operating with and without the specific component or system under evaluation. Accuracy capability employing this test technique is either ±1% or ±2%, depending upon the method of fuel measured. (See paragraph 7.4.)

The testing technique outlined in this recommended practice was developed as part of an overall program for testing and evaluating fuel consumption of heavy-duty trucks and buses. The technique outlined in this recommended practice provides a general description of the type of equipment and facility which is necessary to determine the power consumption of these engine-driven components. It is recommended that the specific operating condition suggested throughout the test be carefully reviewed on the basis of actual data obtained on the specific vehicle operation. This recommended practice covers evaluation techniques for determining the power consumption characteristics of hydraulic pumps used on heavy-duty trucks and buses.