Crocodile (train control system)

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Crocodile

Crocodile refers to a component of various train control systems devised in 1872 by engineers Lartigue and Forest of the Compagnie des chemins de fer du Nord . These systems are now considered to be very insecure and are replaced by other systems, e.g. B. KVB added.

The device is used today in France, Belgium and Luxembourg, but is to be replaced in the long term by ETCS equipment.

In Belgium and Luxembourg it is part of the train control systems Memor and Memor II + , in France the systems Répétition des signaux ( RS for short , signal repetition ) and Dispositif d'arrêt automatique des trains ( DAAT for short , device for automatically stopping trains ).

Due to the railway accident in Buizingen , work will be intensified until 2015 to equip the Belgian network with the TBL1 + system , which is supposed to offer more safety.

construction

Brush on the underside of the locomotive

A steel bridge - the crocodile - is attached between the rails. A voltage is applied to the crocodile to influence the vehicle equipment. A brush ( brosse ) is attached to the motor vehicle and transfers this voltage to the receiver. This transmission is also called an impulse. Depending on the voltage, the vehicle equipment is influenced accordingly:

  • at +20 V to earth or the rails, there is a restrictive influence ( signal fermé - closed signal). At the time of development, this activated a whistle that had to be reset by the driver. The function of emergency braking if there was no reaction from the driver was added later. Both the impulse and its acknowledgment were noted on the tachograph with a vertical line.
  • at −20 V compared to earth or the rails ( signal ouvert - open signal) there was only a corresponding documentation on the tachograph without activating the whistle. This voltage was applied to signals with the concept of travel in order to be able to analyze the tachograph better.

Cab equipment

In the event of a positive influence, the horn sounds and a yellow lamp (signal repeat lamp) starts to flash. If knowledge of the influence is confirmed, the yellow lamp lights up continuously until the next negative influence, but can also be switched off by the driver himself.

“The power source is located on the route near the signal in a special battery box or in a guard shack. About 200 m in front of the signal, the fixed contact rail (the so-called "crocodile") is insulated on the track between the rails. It consists of a brass-studded wooden beam that is slightly rounded at the front. A brush made of copper wires hangs from the locomotive, isolated from it. In the driver's cab there is a steam whistle that is activated by a magnetic switch when the electromagnet receives power. This happens when the brush brushes over the contact rail when the signal is closed. The following electrical circuit then arises […]: From the battery via the brass coating of the contact rail and the brush into the coils of the electromagnet, from there via the axles and wheels of the locomotive to the rails and via the disk contact back to the battery. If the signal is set to "Drive free", the line at the window contact is interrupted. In this case the symbol does not appear on the locomotive. The facility uses working power. Poor contact, failure of the battery, breakage of a lead wire makes it ineffective. Despite these shortcomings, many thousands of them are in operation on the northern runway. "

- Hoogen (1912)

functionality

Yellow lamp in the driver's cab in warning position after passing a distant signal

A crocodile is usually attached to all signals with distant signals (ie pure distant signals, combined main / distant signals (multi-section signal) and the disque). Various slow speed signals are also equipped with crocodiles. If a locomotive passes a distant signal in warning position, the driver has 5 seconds to acknowledge the influence, otherwise an emergency brake is triggered. The system does not check whether and to what extent the driver is braking the train.

  • At pre-signals in the warning position (expect stop, expect slow travel) and slow travel signals , the Crocodile has a voltage of +20 V, the signal must be acknowledged as described above. Only in the French variant RS does an acoustic signal sound when influenced. There is no signal in Belgium, and there the drivers are supposed to acknowledge the signal before it is influenced and hold the acknowledgment switch until the signal passes (similar to the operating action on the German PZB). In Belgium, subsequent operation is also possible, but is recorded as such on the data recorder.

A yellow lamp was added later, which lights up until the next signal after the acknowledgment and is intended to remind the driver of the distant signal in the warning position. With this, the gong-fluit-system was further developed to memor (from memorize ) in Belgium . In February 2010, 154 vehicles (corresponding to 11%) from Infrabel and NMBS / SNCB did not have a memor, but only the older gong-fluit system, which does not remind the train driver to drive past a distant signal in a warning position.

  • A voltage of −20 V is applied to the Crocodile at the main signals in the driving position (driving, slow driving). In Belgium (MEMOR), a gong sounds on newer vehicles; the yellow lamp also goes out. In France (RS) there is no audio signal, but the signal is recorded on the data recorder.
  • At STOP field-side main signals no voltage is present at the Crocodile. It is assumed that if the signal indicating a stop is not allowed to pass, the absence of the gong sound, as it sounds when signals indicating travel are passing, is recognized and the train driver evaluates this correctly.

Memor II +

After three tragic accidents in Luxembourg (1997), the system there was expanded to become Memor II +. On the one hand, the Memor II + checks a braking curve so that 800 m after influencing a speed of 60 km / h must be reached, otherwise an emergency brake is initiated. The lack of automatic braking when the main signal shows stop is still problematic . Therefore, with the Memor II +, two crocodiles are placed one behind the other at a main signal at a maximum distance of 11 meters. If these two crocodiles have a positive potential at the same time, an emergency brake is initiated with the appropriate vehicle equipment.

The name of the system indicates its ability to force-brake a train when it passes a main signal indicating a stop (two positive pulses).

The upgrade of the network in Luxembourg was completed in 2004, and the entire rail network has had ETCS track equipment since the end of 2014. The final conversion of all vehicles to ETCS must take place by January 1, 2021.

Individual evidence

  1. ↑ M. Cossmann. Note sur le crocodile Lartigue & Forest en service sur le réseau du Nord . Revue générale des chemins de fer et des tramways . February 1900. pp. 131-137. Available online
  2. ↑ Dispositifs de sécurité et automatismes embarqués. Retrieved July 14, 2020 (safety devices and automatisms carried).
  3. ↑ SAM S 703 - Répétition des signaux et dispositif d'arrêt automatique des trains - V2. Retrieved July 14, 2020 (signal repetition and device for automatically stopping trains).
  4. ↑ More than 2,550 signals equipped with TBL1 + ( memento from July 17, 2013 in the web archive archive.today ), Infrabel press release from December 9, 2011.
  5. ^ Victor von Röll : Encyclopedia of the Railway System . 2nd Edition. Urban & Schwarzenberg, Berlin / Vienna 1923 ( zeno.org [accessed on May 13, 2019] Lexicon entry “Driver's cab signals”).
  6. ↑ Declaration of the Belgian train control system (Dutch) , accessed on July 17, 2013.
  7. ↑ Investigation report on the Buizingen train accident on February 15, 2010, in Dutch (PDF; 6.7 MB) and in French (PDF; 7.9 MB), Section 3.4.2.4.
  8. ↑ Investigation report on the Buizingen train accident on February 15, 2010, in Dutch (PDF; 6.7 MB) and in French (PDF; 7.9 MB), Sections 7.7.2 and 7.7.3.

Web links

Commons : Crocodile  - collection of images, videos and audio files