At the start of the project in 1994, there was no discipline such as tunnel safety. Good regulations in this area were lacking and the construction decree fell seriously short of what was required for an underground station. The importance of the subject was strongly emphasized by a number of major tunnel incidents with many casualties, such as in Baku in 1995. Tunnel safety is about fire and crowding, about smoke development and the flow of people. How to evacuate as many people as possible in the shortest possible time.
To guarantee safety in the North/South Line, a whole range of measures has been devised. The North/South Line is quite unique, with deep stations and compact tunnels. People must have enough options to escape. This was something to take into account from the start of the design. Escape can be done by means of escape shafts, which are kept under overpressure to stop smoke, there are cross passages between the tunnels and the escalators are also necessary for evacuation. It was against the rules to use escalators for this purpose. Authorisation took years.
We also use the safe harbour concept, whereby the metro only leaves from one station when there is room for it at the next station. Many visible and invisible measures have been taken to maximise safety. This project has really set a standard here. The solutions that have been devised here have now also been used elsewhere, for example for the station in Delft and the metro in Brussels. It is a well thought-out integral safety system, in which a great deal has been invested.