A method and device for estimating the operating time of a motor vehicle in autonomous mode for at least one route between a departure point and an arrival point. The estimating device is connected to an identifying element and to an element for characterizing portions of roads approved for the operation of the vehicle in autonomous mode, along the at least one route. The estimating device includes a unit for calculating the time during which the vehicle is eligible to operate in autonomous mode depending on the characterization of approved portions of road.