An approach warning system includes at least one marking module and a warning module. The at least one marking module comprises a marking module transmission unit configured to emit electromagnetic signals, and a motion detector configured to detect a motion. The at least one marking module is configured to emit presence signals as the electromagnetic signals when a motion is detected. The warning module comprises a reception unit configured to receive the electromagnetic signals emitted by the at least one marking module, and an output device configured to emit an approach warning. The warning module is configured to emit the approach warning via the output device dependent on a reception of the presence signals emitted by the at least one marking module.