Abstract: The invention refers both to a method of converting a vehicle, such as a truck, a tractor, a lorry or the like and to a steerable working machine for specific working purposes, e.g. a hammer arrangement for making holes, or a drilling machine and to a combined vehicle and working machine. The working machine (30) in question is mounted on the chassis of the vehicle (1) and is arranged to be operated from an operating location (9) which is fixed or movable relative to the vehicle. The vehicle is provided with an additional driving mechanism (23-25), e.g. a hydraulic motor having a driving element (25) which can be moved between an active and an inactive position and which is arranged to engage the vehicle wheels (3) or the vehicle transmission system (20, 21, 22) for slowly propelling the vehicle and a separate remote-control means (12-16) actuating the vehicle steering system (10, 11). The drive mechanism (23-25) and the remote-control means (12-16) are operated from said operating location (9).