Six different experimental methods for measuring braking efficiency have been utilized and evaluated by the National Highway Traffic Safety Administration at its Vehicle Research and Test Center. This work has been performed in support of international efforts to harmonize passenger car braking regulations. Four of the methods are similar in that they measure brake force distribution at one or more braking rates on high coefficient of friction surfaces and calculate braking efficiency as a function of a hypothetical peak tire/road coefficient of friction (mu). The other two methods measure maximum non-locked wheel deceleration of the vehicle on a particular surface and then rely on measurement of mu to calculate effrciency for that particular surface. Generally, the four methods utilizing the brake force measurement approach produce similar results, although one of these four is a very low-speed test that does not necessarily predict efficiency at higher speeds. The other two maximum deceleration-based methods do not necessarily produce similar results due to the fact that they measure a somewhat "different" braking efficiency.