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BACKGROUND Powertrain developers have suggested that slip at the vehicle tire and chassis dynamometer contact point for US06 emissions testing causes unmanageable variability. In order to counteract slip, some developers have been requesting their vehicles be strapped down tighter. Strapping a vehicle down tighter may lead to unrepresentatively low fuel economy and high emissions (many tests are run FTP/Hwy/US06 consecutively). EXPERIMENT A study was developed to investigate the effects of dynamometer roll surface roughness and vehicle restraint strap tension on fuel economy, emissions, and the amount of wheel slip. In addition, a correlation may be established between wheel slip and fuel economy and emissions. A three factor, two-level, full factorial design with three replicates was planned. The factors were dynamometer surface roughness, vehicle, and strap tension.