Control apparatus for ventilating a tunnel

This application claims benefit of priority to Japanese Patent Application No. 11-258887 filed Sep. 13, 1999, the entire content of which is incorporated by reference herein. A control apparatus for a ventilator that ventilates a tunnel in response to visibility of the inside of the tunnel, including at least one picture image input device configured to take a picture of the inside of the tunnel, a visibility index determination device configured to determine a visibility index value on the basis of a picture image data of the picture taken by the picture image input device in light of a table representing a relationship between the picture image data and the visibility index value, a feedback controller configured to calculate an operation command for operating the ventilator on the basis of a feedback control value calculated by comparing the visibility index value with a target value of the visibility index value.