PURPOSE: To surely secure the rainning path of an emergency vehicle by displaying a display pattern on a display when a specific signal is received from the emergency vehicle.

CONSTITUTION: A running signal representing the running direction of the emergency vehicle is supplied from an operation managing center to a display device located at the running route of the emergency vehicle. The running signal is received by the control part of the display device, then, when the emergency vehicle issues the specific signal, the specific signal is detected, and the display pattern is displayed on the displays 1-4. A signal code and the display pattern are recorded correspondingly on the memory of the display device. The signal code is equivalent to the running signal outputted from the center, and it consists of an entrance code and a leaving code. For example, a code (0000) shows the case that (the vehicle enters from the north and it performs U-turn at a cross and it leaves to the north), and a code (0010) shows the case that (the vehicle enters from the north and it goes straight on at the cross, then, it leaves to the south). The display patterns of four displays 1-4 are recorded with the signal codes.