Method and system for controlling the cruising speed of a vehicle

A method for controlling the cruising speed of a motor vehicle, in particular a heavy industrial motor vehicle, the method envisaging: setting a desired cruising speed for the motor vehicle; and managing the longitudinal motion of the motor vehicle in order to reach and/or maintain the desired cruising speed automatically. According to the invention, there are further envisaged: detection or estimation of the altimetric profile of the road on which the motor vehicle is travelling; determination, according to the altimetric profile of the road detected or estimated, of a cruising speed considered optimal for the motor vehicle; and determination of the gear ratio.