An autonomous mobile surface treatment vehicle for driving on a surface, the surface treatment vehicle comprising - an autonomy system arranged to output speed and direction control signals for navigating the autonomous mobile surface treatment vehicle according to a map or intended route, - a sensor system arranged to sense speed and direction of the autonomous mobile surface treatment vehicle and to output speed and direction estimate signals accordingly, the sensor system further comprising a scanning sensor arranged to scan a scan area around the autonomous mobile surface treatment vehicle for determining a position of an obstacle within the scan area and to generate a detection signal accordingly, - a safety system arranged to receive the speed and direction estimate signals and to select a safety zone relative to the autonomous mobile surface treatment vehicle accordingly in response to a safety zone selection algorithm, and wherein the safety system is arranged to receive the detection signal, and to generate a safety stop signal in case the detection signal indicates an obstacle within the safety zone, - a controllable propulsion motor or motors for controlling drive speed of the autonomous mobile surface treatment vehicle, - a controllable steering mechanism for controlling drive direction of the autonomous mobile surface treatment vehicle, and - a controller arranged to receive speed and direction control signals, and to control the propulsion motor or motors and the steering mechanism for driving the autonomous mobile surface treatment vehicle at speed and direction in response to the speed and direction control signals, wherein the controller is further arranged to control the propulsion motor or motors and/or a brake to bring the autonomous mobile surface treatment vehicle to a stop in case a safety stop signal is received, - characterized in that the safety system is arranged to switch from a first mode of operation where a first safety zone selection algorithm is executed as the safety zone selection algorithm to a second mode of operation, where a second safety zone selection algorithm is executed, the second safety zone selection algorithm arranged to select a safety zone which allows a higher speed under the restriction of a more narrow direction angle compared to a safety zone selected by the first safety zone selection algorithm, and wherein the first and second safety zone selection algorithms select the safety zone in different ways. - an autonomy system arranged to output speed and direction control signals for navigating the autonomous mobile surface treatment vehicle according to a map or intended route, - a sensor system arranged to sense speed and direction of the autonomous mobile surface treatment vehicle and to output speed and direction estimate signals accordingly, the sensor system further comprising a scanning sensor arranged to scan a scan area around the autonomous mobile surface treatment vehicle for determining a position of an obstacle within the scan area and to generate a detection signal accordingly, - a safety system arranged to receive the speed and direction estimate signals and to select a safety zone relative to the autonomous mobile surface treatment vehicle accordingly in response to a safety zone selection algorithm, and wherein the safety system is arranged to receive the detection signal, and to generate a safety stop signal in case the detection signal indicates an obstacle within the safety zone, - a controllable propulsion motor or motors for controlling drive speed of the autonomous mobile surface treatment vehicle, - a controllable steering mechanism for controlling drive direction of the autonomous mobile surface treatment vehicle, and - a controller arranged to receive speed and direction control signals, and to control the propulsion motor or motors and the steering mechanism for driving the autonomous mobile surface treatment vehicle at speed and direction in response to the speed and direction control signals, wherein the controller is further arranged to control the propulsion motor or motors and/or a brake to bring the autonomous mobile surface treatment vehicle to a stop in case a safety stop signal is received, - characterized in that the safety system is arranged to switch from a first mode of operation where a first safety zone selection algorithm is executed as the safety zone selection algorithm to a second mode of operation, where a second safety zone selection algorithm is executed, the second safety zone selection algorithm arranged to select a safety zone which allows a higher speed under the restriction of a more narrow direction angle compared to a safety zone selected by the first safety zone selection algorithm, and wherein the first and second safety zone selection algorithms select the safety zone in different ways.