A system includes a laser displacement sensor which is provided on a shoulder of a roadway, emits a laser beam which scans a roadway space in a height direction thereof, receives a beam reflected by an object which is present in the roadway space, and measures a distance up to a reflection point on the object, at which the laser beam was reflected; and a vehicle window detection device that detects a window of the vehicle based on the distance measured by the laser displacement sensor. The vehicle window detection device detects the window of the vehicle based on a change in a distance in a horizontal direction from the laser displacement sensor to the reflection point after the vehicle in the roadway space was detected.