Abstract: In a first distance range to the obstacle, the velocity of the vehicle is limited by the control of the power of the drive unit of the vehicle. In a second distance range which is less than said first distance range, the braking force at the wheel brakes is built up.

Abstract: The invention is directed to a process for the production of aluminium alcoholates by reacting aluminium in comminuted form with an excess of an aliphatic C.sub.3 to C.sub.10 alcohol in which the aluminium is supplied to the reactor from above and is brought into contact with an aluminium alcoholate/alcohol mixture above a perforated plate or grid tray (screen) in the reactor. The aluminium, or preferably a suspension of alcohol and finely divided aluminium, is supplied to the reactor and fed from above to a bubble bed made of a mixture of aluminium alcoholate and alcohol in the area of the perforated plate, whereby the mixture of aluminium alcoholate and alcohol in the reactor sump or overflowing in part is recycled to the reactor over the bubble bed and optionally, preferably with the aluminium suspension, returned from above to the reactor and in part is isolated. There is also described a reactor suitable for carrying out the process.