Linienzugbeeinflussung

Linienzugbeeinflussung (or LZB) is a cab signalling and train protection system used on selected German and Austrian railway lines as well as on the AVE and some commuter rail lines in Spain. The system was mandatory where trains were allowed to exceed speeds of 160 km/h (99 mph) in Germany and 220 km/h (140 mph) in Spain. It is also used on some slower railway and urban rapid transit lines to increase capacity. In German, the word Linienzugbeeinflussung translates to continuous train control, or more literally: linear train influencing. It is also occasionally called linienförmige Zugbeeinflussung.

LZB is deprecated, and is to be replaced with the European Train Control System (ETCS) between 2023 and 2030. It is referenced by European Union Agency for Railways (ERA) as a Class B train protection system in National Train Control (NTC). Driving cars mostly have to replace classical control logic to ETCS Onboard Units (OBU) with common Driver Machine Interface (DMI). Because high performance trains are often not scrapped or reused on second order lines, special Specific Transmission Modules (STM) for LZB were developed for further support of LZB installation.

In Germany the standard distance from a distant signal to its home signal is 1,000 metres (3,300 ft). On a train with strong brakes, this is the braking distance from 160 km/h. In the 1960s Germany evaluated various options to increase speeds, including increasing the distance between distant and home signals, and cab signalling. Increasing the distance between the home and distant signals would decrease capacity. Adding another aspect would make the signals harder to recognize. In either case, changes to the conventional signals wouldn't solve the problem of the difficulty of seeing and reacting to the signals at higher speeds. To overcome these problems, Germany chose to develop continuous cab signalling.

The LZB cab signalling system was first demonstrated in 1965, enabling daily trains at the International Transport Exhibition in Munich to run at 200 km/h. The system was further developed throughout the 1970s, then released on various lines in Germany in the early 1980s and on German, Spanish, and Austrian high-speed lines in the 1990s with trains running up to 300 km/h (190 mph). Meanwhile, additional capabilities were built into the system.

LZB consists of equipment on the line as well as on the trains. A 30–40 km segment of track is controlled by a LZB control centre. The control centre computer receives information about occupied blocks from track circuits or axle counters and locked routes from interlockings. It is programmed with the track configuration including the location of points, turnouts, gradients, and curve speed limits. With this, it has sufficient information to calculate how far each train may proceed and at what speed.

The control centre communicates with the train using two conductor cables that run between the tracks and are crossed every 100 m. The control centre sends data packets, known as telegrams, to the vehicle which give it its movement authority (how far it can proceed and at what speed) and the vehicle sends back data packets indicating its configuration, braking capabilities, speed, and position.

The train's on-board computer processes the packets and displays the following information to the driver:

If there is a long distance free in front of the train the driver will see the target speed and permitted speed equal to the maximum line speed, with the distance showing the maximum distance, between 4 km and 13.2 km depending on the unit, train, and line.