In this paper, the transient brake time was studied on the van type vehicle with accelerometer. Experiments were carried out on the asphalt(new and polished), unpacked road{earth and gravel) and on wet or dry road conditions. The transient brake time is not effected bzy the vehicle speed. The transient brake time is about 0.41~0.43second on the asphalt road surface and the error range is within 0.1~0.16second. For the asphalt road condition, the transient brake time is not effected by both new asphalt road surface and the polished asphalt road surface. With compared by dry and wet road surface condition, the transient brake time of wet condition is longer than dry road condition and compared with unpacked road condition and packed road condition, unpacked road condition is shorter than packed road condition. It is considered that the transient brake time is effected by the road surface fraction coefficient. In other words, the transients brake time increases as friction coefficient decreases.
