SNCF Z 27500 27628L'Hospitalet-pres-l'Andorre L'Hospitalet-pres-..

This tunnel is special because it have a automatic doors that open before the circulations of the train and closes after the pass of this.

This is a little time-lapse of the moment of the closement of the doors:

Is it for security reason?

Yes Mikhail, is for reasons of safety, to avoid that in winter ice blocks being created due to cold flowing and humidity inside the tunnel.

Thanks, this is really interesting.