PURPOSE: To previously prevent any accident, involving both a human life, and a vehicle, of a runway vehicle due to block angle part from spreading, by the reason of placing, directly on a roadway, a group of blocks for supporting the base parts of posts to which guard rails, etc., are fitted.

CONSTITUTION: At least the lower position on the roadway side of concrete blocks 3 arranged at desired intervals is protected by a guard rail 2A as a belt-like protection wall, and the block 3 group are connected to the wall. In addition, another guard rail 4 is similarly fitted on the upper position of the block 3 on the roadway side.