SICHERHEITSVORRICHTUNG FUER FAHRZEUGE MIT FREMDKRAFT-LENKANLAGEN

A vehicle having at least two servo- steering systems (20,21,22 and 23,24,25) is provided with a safety device by which the two steering systems are switched on alternately (26) in a predetermined sequence the function of the two steering systems being continuously monitored and, upon the occurrence of a fault, the trouble-free steering system is switched on or remains switched on. In the case of trackless vehicles guided by a guide cable, continuous monitoring is effected by superimposing on the field of the guide cable a diagnostic field from a diagnostic transmitter (31), and checking whether the steering systems process this diagnostic field correctly with respect to function. For this purpose a microprocessor (30) compares the received diagnostic signal with a reference, and also compares with input to a functioning hydraulic unit (22,25) with its output to the steering gear (13).