Due to the nature of the system, track-guided systems require a special device for a change of “lane” – the switch.
Switches make it possible to change from one track to another without interrupting the journey. They are therefore a prerequisite for operational flexibility.
- high resistance to static and dynamic loads
- no speed restrictions in the main track
- possibility of adaptation to the line layout without special constructions
- safe closure of the turnout, avoidance of track widening
- “cutting” must be possible without destroying the turnout and without derailment
- Economic efficiency (acquisition and maintenance costs)
Since switches always represent a point of increased risk due to their function, special requirements are placed on the design, monitoring of the switch setting (safety systems) and maintenance.
- Misalignment (failure of the safety devices)
- Excess speed in the deflection (human error, e.g. Brühl accident)
- Material failure (tongue fracture, etc.)
- Overturning of already derailed vehicles (failure of track guidance, e.g. Eschede accident)
The Eschede accident resulted in numerous consequences with regard to the arrangement of switches in the route (in particular for tunnel sections, crossing structures, superstructures).
Types of switches
Simple switches (SS)
consist of one straight and one curved track.
Double turnouts (DT)
as two simple turnouts pushed into each other. There are single-sided double turnouts (both branches on the same side) and double-sided double turnouts (branches on different sides).
consist of a track intersection (crossing) and one or two connections between the crossing tracks. There are single crossing points (SCP) or double crossing points (DCP).
consist of two curved tracks. If both curves are curved in the same direction, they are called inner curve turnouts (ICT), if they are curved in the opposite direction, they are called outer curve turnouts (OCT).
Choice of the type of turnout
The choice of the type of turnout depends on
- the desired route and branching speed of the line routing
- the available track lengths for the development of the “turnout lines
- the available construction types (not all construction types are available in every rail form)
and is influenced by
- construction costs
- maintenance costs
- safety considerations
Complex designs such as SCP and DCP cause disproportionately high maintenance costs and are more prone to failure compared to simple switches.