Abstract: The invention relates to emergency braking of a tractor trailer or other automotive vehicle especially in a final panic situation prior to total loss of control. The present invention relates to a mechanical skid which is carried below the body of a tractor trailer just forward of the rear wheels. If the trailer wheels should lose traction or if the braking system should fail, the skid is dropped onto the roadway immediately in front of the rear wheels. The tractor's rear wheels roll onto the skid where they make contact with a vertical barrier which is part of the skid. The skid is then forced to slide along the road surface with the trailer's wheels on top of it until coming to a halt. The skid acts to provide a substantial increase in stopping power over that available through the brakes and tires alone. The bottom surface of the skid provides a much larger surface area in contact with the road than is provided by the tires.