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Track equipped with LZB loops. Notice the second cable on the lower part of the left rail.


Linienzugbeeinflussung (or LZB) is a cab signalling and train protection system used on selected German and Austrian railway lines as well as the AVE in Spain. In Germany, the system is mandatory on all lines where trains exceed speeds of 160 km/h (200 km/h in Spain), but it is also used on some slower lines to increase capacity. The German Linienzugbeeinflussung translates to continuous train control, literally: linear train influencing. It is also called linienförmige Zugbeeinflussung.


Overview

Sign indicating a new (virtual) LZB block

In Germany, the standard distance from a distant signal to its home signal is 1,000 m. On a train with strong brakes, this is the braking distance from 160 km/h. To enable safe operation at higher speeds, the distance from the distant signal to home signal would have to be increased. As this also increases the minimal distance from one home signal to the next (two blocks of distant/home signal cannot overlap) and therefore decreases the number of trains a line can handle, this is undesirable. The solution was the move from a point-based (at each signal) to a linear (continuous) train control.


Computers

LZB antenna on a DB Class 423 (S-Bahn Munich)

The LZB consists of several sets of computers, both at the control center and the train, that continuously exchange data. Data is exchanged using two conductor cables that run between the tracks and that are crossed every 100 m. This enables a continuous flow of data packet (so-called telegrams) and a precise localisation of the train. Additionally, there are usually conventional track-side signals for trains not equipped with LZB. Under special circumstances, when a signal would show a red light, but the LZB could safely lead the train past the signal, the signal is switched off for psychological reasons to avoid confusion for the driver.


Cab signals

Main console of an ICE 2 train in LZB mode. The current, the maximum and the target speed is 250 km/h. The target distance ist 9.8 km

In the cab, the driver receives additional information compared to what they would see without LZB. Additionally to the current speed, there is a display indicating the distance to an (arbitrary) target point and the speed that the train should have at that target point. If the train's computer decides that, based on the train's braking characteristics, the target speed cannot be reached, it initiates an emergency stop. Another system, the AFB (Automatische Fahr- und Bremssteuerung, automatic driving and braking control), enables the driver to let the computer drive the train on auto-pilot, automatically driving at the maximum speed currently allowed by the LZB. In this mode, the driver only monitors the train and watches for unexpected obstacles on the tracks.


Adoption

First tests of the LZB were conducted in 1963, well before the first plans for an ICE network. In 1965, some demonstration runs were driven at 200 km/h between Munich and Augsburg. Starting in 1974, the system was deployed to selected lines.


Equipped lines

DB

The following lines of Deutsche Bahn are equipped with LZB, allowing for speeds in excess of 160 km/h (providing the general suitability of the track):



Note: italics indicate the physical location of an LZB control center.


ÖBB


RENFE

Since 2004, the terminus Madrid­Atocha is also equipped with LZB.


In November 2005, a branch line to Toledo was opened. (20 km).


  • Cercanías Madrid line C5 from Humanes over Atocha to Móstoles-El Soto.

45km  track length with 2 LZB centres and 76 vehicles of Series 446.

  • All EuskotrenBideak network with the exception of the Euskotran network.


Other uses

LZB technology is not only used on main line rail, but also on U-Bahn and Stadtbahn networks. For example, the tunnels of the Düsseldorf Rheinbahn are equipped with LZB. The K-Bahn of the same operator is also equipped with LZB, however there it is used for telemetry purposes only. Furthermore, the tunnel of the Munich S-Bahn between the stations Laim and Ostbahnhof is equipped with the LZB successor LZB L72 CE II.


See also

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