System to secure lockable doors with people manholes of passenger transport vehicles

The invention relates to a system for securing closable with doors passenger door openings of vehicles for passenger transport, in particular rail vehicles, with at least one sensor having a light receiver for detecting radiation from a first fan-shaped monitored zone which extends approximately parallel to a vehicle door at an outer side of the vehicle extends, and for detecting radiation from a second fan-shaped monitored zone which is tilted with respect to the first monitored zone and includes a tilt angle therewith. can be to provide an improved system for protection, saving the cost and operates as reliably as possible, it is proposed that the sensor comprises a transmitter for transmitting transmitted light in the first and / or second monitored region and that the deflected in the monitoring areas transmit light monitoring levels forms.