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This document describes a rigorous-engineering fuel-consumption test procedure that utilizes industry accepted data collection and statistical analysis methods to determine the change in fuel consumption for individual trucks and buses with GVWR of more than 10000 pounds. The test procedure may be conducted on a test track or on a public road under controlled conditions and supported by extensive data collection and data analysis constraints. The on-road test procedure is offered as a lower cost alternative to on-track testing, but the user is cautioned that on-road test may result in lower resolution (or precision) data due to a lack of control over the test environment. Test results that do not rigorously follow the method described herein are not intended for public use and dissemination and shall not be represented as an SAE J1321-Type II test result.

This document describes a rigorous-engineering fuel-consumption test procedure that utilizes industry accepted data collection and statistical analysis methods to determine the change in fuel consumption for trucks and buses with GVWR of more than 10,000 pounds. The test procedure may be conducted on a test track or on a public road under controlled conditions and supported by extensive data collection and data analysis constraints. The on-road test procedure is offered as a lower cost alternative to on-track testing but the user is cautioned that on-road test may result in lower resolution (or precision) data due to a lack of control over the test environment. Test results that do not rigorously follow the method described herein are not intended for public use and dissemination and shall not be represented as a J1321-Type II test result.

This recommended practice provides a standardized test procedure for comparing the in-service fuel consumption of two conditions of a test vehicle or of one test vehicle to another when it is not possible to run the two or more test vehicles simultaneously. An unchanging control vehicle is run in tandem with the test vehicle(s) to provide reference fuel consumption data. This procedure is especially suitable for testing components which require substantial time for removal and replacement or modification, such as engines, transmissions, tag-axles, and cab sheet metal. This procedure may also be used for comparison of entire vehicles and for easy-to-change components (those referenced in the Type I test described in SAE Recommended Practice, SAE J1264). The test may utilize fleet vehicles operating over representative routes.