Abstract: Proposed is a new early warning system for warning persons in a track building site of approaching trains, which receives the danger source consisting of a train by sensors and transmits the signals to alarm installations (8, 9, 10). The alarm installations consist of a siren (8) and optical warning device (10) for the transmission of flashing lights and of a vibrator (9) which can be carried at the body of a person to be warned. The sum of these three alarm installations in connection with suitable sensors (11) and an evaluating unit or central unit form the nucleus of the system.