1. Method of detecting vehicles on at least one stretch of a carriageway implementing: an acoustic detection comprising a step of acquiring and processing the sound originating from at least one zone, termed the acoustic monitoring zone, of the stretch of carriageway; and at least one detection chosen from: a video detection comprising a step of acquiring and processing the video images of at least one zone, termed the video monitoring zone, of the stretch of carriageway; a radar detection comprising a step of emitting a microwave electromagnetic radiation towards at least one zone, termed the radar monitoring zone, of the stretch of carriageway and a step of acquiring and processing the microwave electromagnetic radiation reflected, and comprising at least one step of processing the results of the optical and/or sound and/or radar detections so as to deliver an item of information regarding the presence or absence of at least one vehicle.