Counter-run protection

Under the counter underrun protection is understood to measures to prevent two trains down one another frontally on a track in the opposite direction and there occurs a collision (collision).

A distinction is made between counter-vehicle protection in stations and on the open road .

Train stations

In train stations, counter-run protection is only implemented using the route logic. Special route exclusions in the signal box prevent two signals from being set to travel at the same time, which would allow two trains to travel on the same track.

Free route

In order to ensure counter-vehicle protection on track tracks that are used on both sides, i.e. single-track lines and double-track lines with track changing operations, the dispatchers at the two train detection points agree in which direction the route section may be traveled (so-called permission ). The permit can only be in one station and is coordinated with the other station via lines. It is only possible to change the agreed direction of travel (change of permit ) if the last train traveled has cleared the track. With some block designs, the license change can be triggered when the last train has left the station ("the license is given"), but the actual license change does not take place until the section has been cleared.

In relay interlockings and electronic interlockings that control several adjacent train detection points, the permit is usually reproduced centrally in the interlocking. It then changes automatically when a route is set. However, once the route has been determined, a change of permit is no longer possible. Due to the route logic (block routes ), this only serves to prevent getting stuck, since the occupancy of a track section by two routes is already excluded due to a special route exclusion. In some signal boxes, however, a special route exclusion is used instead of a permit. Opposite routes can no longer be set as soon as a train has entered the route section. It is therefore not possible to partially drive on a track from both sides up to one block signal each. If such journeys are to be implemented operationally, for example branch journeys to stops on the free route, the journey must be carried out as a restricted journey . For trains running regularly, all that remains is to include the free route in a neighboring station as part of the station or to introduce a "switch-free station", that is, a station that, as an exception, has no switches. However, this requires the establishment of route logic and adjustments to the route block. Stations without switches are announced at Deutsche Bahn in the register of slow-moving areas.

On double-track lines with an established track change operation , it is possible to set up a preferred position for the change of permit (»Change of permit form V«). As a rule, it is then located at the point where the journeys into the regular track begin. For each trip against the normal direction of travel, it has to be returned individually and returns automatically with each of these trips.

In some older systems, which are no longer used in Germany, counter-vehicle protection is provided through an individual permit. The accepting train registration office must issue the permit individually for each train journey. With this method, the division of the single-track line into several block sections is very complex.

The oldest form of counter-run protection are token systems , in which the last train in a direction of travel is given a token that must be available for release at the departing operating point. The Radio Electronic Token Block derived from it is still used sporadically in Great Britain today.

Residual risk

There is a risk of human error if the technical equipment is disturbed and therefore auxiliary actions are taken.

These led to serious accidents , such as the railway accident in Dahlerau and the railway accident in Bad Aibling .

literature

W. Fenner , P. Naumann, J. Trinckauf : Bahnsicherungstechnik , Publics Corporate Publishing 2003, ISBN 3-89578-177-0

Individual evidence

↑ ^a ^b ^c ^d Jörn Pachl: System technology in rail transport: planning, controlling and securing rail operations . 7th edition. Springer Science + Business Media, 2013, ISBN 978-3-8348-2586-5 , 3.3 Securing driving in fixed spaces , p. 59 , doi : 10.1007 / 978-3-8348-2587-2 .

[Pachl-1] Jörn Pachl: System technology in rail transport: planning, controlling and securing rail operations . 7th edition. Springer Science + Business Media, 2013, ISBN 978-3-8348-2586-5 , 3.3 Securing driving in fixed spaces , p. 59 , doi : 10.1007 / 978-3-8348-2587-2 .