Abstract: The invention relates to a safety device for selectively track-guided or road-travelling vehicles, which safety device exhibits on the road side an optical indicator device switched by a control device and normally set to "stop" signalling. In order to permit a change of the vehicle from track-guided to non-track-guided operation only when the sensing rollers are fully retracted, the invention provides that both a monitoring device monitoring the assumed rest position of the sensing rollers and signal transmission device coupled therewith are provided on the vehicle side. The signal transmission device transmits a signal indirectly switching the optical indicator device temporarily to "go" only in the case of the sensing rollers occupying the rest position.