The invention provides an autonomous surface treatment vehicle, e.g. a floor cleaner, with an autonomy system navigating according to a map, a scanning sensor to detect a position of an obstacle within a scanning zone and generate a detection signal. A safety system is arranged to generate a safety stop in case the detection signal indicates an obstacle within a safety zone. The safety system can enter a special mode of operation, e.g. upon request from the autonomy system, where a special safety zone selection algorithm selects the safety zone e.g. from a special set of pre-determined safety zones. Especially, such special mode can provide safety zones with a relaxed speed limit in combination with a restricted direction limit, so as to provide a faster driving near a wall or similar known obstacle.