The tunnels and underground stations have a large number of technical systems, some of which are specially adapted for Citytunneln.
The technical installations include track systems, contact wires, electric power, radio communication, signal systems, and telephone transmission. Of Citytunneln’s 17 km of track, 11 km is located above ground. On these stretches, the same technology is used as on other railway communications in Sweden. In total, there are about 50 switches included in the project.
Unique systems
The underground rail system differs from that on the surface and it’s unique for Sweden. The underground track is laid on concrete instead of ballast. To prevent vibrations from the trains affecting the local environment, the sleepers are laid on elastic, vibration-damping matting, thus meeting the requirements restricting structure-borne sound in the buildings above.
The contact wire system is also specially developed for Citytunneln, because the space between the top of the train and the tunnel roof is limited. The height is 50 cm instead of the normal 100-150 cm. The electric power installations for Citytunneln are extensive, partly because power will be used by a large number of items, and partly because the system is duplicated for safety reasons.
Communication
It is also important that trains remain in contact with the outside world when they are in tunnels, so Citytunneln has various radio communication systems. GSM-R (Railway) is a new European standard for radio connections in the railway sector. The system is used for communication between the trains and the Swedish National Rail Administration’s traffic management centre. Tetra is the authority’s new radio system, used by the rescue service and the police. To allow train travellers to use mobile telephones on the train, there is also coverage for GSM/UMTS. Radio signals for the various systems are amplified and will be distributed via a longitudinal antenna cable suspended in the cable ladders that run along the tunnels.
Signals
The signal system used in Citytunneln is known as ERTMS (European Railway Traffic Management System). This is a new, common system for railways within the EU that can now be used by operators from different countries. However, when the new link opens in December 2010 the existing signal system in Sweden, ATC (Automatic Train Control), will be used. The plan is to switch over to ERTMS later, in 2012.
The system for telecommunication is called transmission, and involves communication between for example remote control, telephones, CCTV and the Swedish National Rail Administration’s traffic management centre. For safety reasons, the system is duplicated.