PURPOSE: To greatly reduce the fear of uncontrolled run and remarkably enhance the safety.

CONSTITUTION: A crawler vehicle is equipped with a traction car 2 where drive wheels 23 are meshed with rack teeth 12 of unit rail 1 and a follower car 3 in which the first and second follower wheels 34A, 34B are meshed with the rack teeth 12 of unit rail 1, wherein a traction side constant speed brake 4 is furnished which is connected with the drive wheels 23 through gears and applies brakes to them 23 when the vehicle speed has exceeded the set value. The arrangement further includes a follower side constant speed brake 5, which is connected with the first follower wheel 34A through gears and applies brakes to it when the vehicle speed has exceeded the set value, and an automatic emergency stop brake 6 which is coupled directly with the second follower wheel 34B and applies brakes thereto when the vehicle speed has exceeded a certain abnormal value higher than the set value.