Abstract: An emergency braking device is attached to the vehicle body and is shiftable between an inoperative position and an operative position upon the occurrence of an emergency braking situation. The braking device is provided with a vacuum shroud which engages the roadway to form a substantially enclosed cavity. The shroud is shifted between the operative and inoperative position by a shifting mechanism. A pump is provided to evacuate air from the enclosed cavity to cause the vacuum shroud to be urged toward the roadway. An attachment device temporarily couples the vacuum shroud to the vehicle wheel causing the normal load of the wheel on the roadway to be increased, enabling the vehicle brake to decelerate the vehicle at an increased rate.