Abstract: A safety apparatus to be mounted on a chassis of a dump vehicle having a dump back movable between a rest position and a dump position. The safety apparatus has a guide member attached to the vehicle chassis to define a closed track. There is a safety prop pivotally attached to the dump back. At the bottom of the safety prop a wheel or the like is attached and is received by and engages the guide member. There is a locking member to retain the safety prop and thus the dump back in a fixed position relative to the guide member when the back is raised to the dump position. The locking member acts to prevent downward movement of the back.