Caution signal

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Signal aspect of the caution signal

The caution signal (Zs 7) is a railway signal from the group of additional signals and is located at main signals .

According to the signal book (guideline 301 of the Deutsche Bahn AG) it orders : “ Drive past the signal Hp 0 or the disturbed main light signal without a written command! Continue on sight. "

The operational actions for a train journey with a special order as well as the requirements for driving on sight must be observed.

Except for certain rare old systems, it is only available as an alternative to a substitute signal ( Zs 1 or Zs 8 ). The signal image reads: " Three yellow lights in the form of a V. "

Technical requirements

A Ks signal with an active caution signal
An H / V signal with an active caution signal

The aim of the caution signal is to replace the written command to drive past the stop when the signal system is disturbed, if it cannot be ensured that the route is free and the train journey must therefore run on sight. In a few rare exceptional cases (see #History ) the signal is switched on fully automatically by interlocking systems, even when the route is secured but not clear, in order to achieve a closer train sequence.

The caution signal is almost only used in relay and electronic interlockings. With mechanical and electromechanical interlockings, an operator can almost always check that the route is clear by looking. In rare individual cases, in which mechanical interlockings covered larger areas with the help of track vacancy detection devices (and usually took over the signals from neighboring interlockings), caution signals were also implemented in mechanical interlockings.

Due to the characteristic as a signal in the event of faults, neither the position nor the closure of the guideway elements is checked by the interlocking. The dispatcher has to take on these tasks (whereby the interlocking systems can support him). Only the responsibility for the clearness of the route can be given to the driver by the caution signal. In times of centralized control of the signal box, checking that the route is clear by looking is virtually impossible. An earlier possibility of vacancy reporting by local supervisors has become obsolete due to its blanket elimination. Wherever they are still present, they usually do not perform such tasks.

Planning guidelines

Symbol of a caution signal (Zs 7) in safety-related plans

The symbol in the safety-related site plan is an open tip pointing downwards, which is above the associated main signal.

The caution signal is primarily used at the entry and intermediate signal to make it easier for the dispatcher to check that the tracks are clear as part of the route inspection, which often cannot be carried out directly by looking at relay interlockings and electronic interlockings . In the event of a faulty track vacancy detection (which, however, can only be one of several causes for faults in the main signals), the connection of the substitute signal Zs 1 is then excluded and a command must be dictated, which the fixed substitute signaling was originally intended to avoid. However, if the track vacancy detection is not disturbed, it would also be necessary to drive on sight with signal Zs 7, although it would not be necessary from an operational point of view.

It is therefore usually a mixed form in new buildings. The caution signal is used for entry and intermediate signals, as there is a higher probability that vehicles are actually on the track and the signal distances are usually no more than 1500 meters. In the case of exit and block signals , the substitute signal Zs 1 is more likely to be used for longer block sections , since the drive on sight ordered by the caution signal would cost too much time here. Faults in the track vacancy detection system are less common on the open line and trains are less likely to come to a standstill on the open line than in the station. The security is always given, so that the differentiation only has an impact on the fluency of the operation (duration of driving on sight compared to the duration of dictating a command).

history

The former route with automatic caution signals between Köln Hbf and Köln Bbf after its conversion into a station track. At the front left, the two optics for Zs1 and Zs 7 can still be seen from the signal 335 from behind.

The caution signal was first introduced in 1951 as an operational test on the heavily loaded connecting tracks between Cologne main station and Cologne main station as the "Zs V - caution signal -" signal. It served a denser train sequence of trains (almost always not occupied with passengers anyway) and was automatically switched on by the system when a train approached but the track was still occupied.

In the version at that time, the driving speed had to be regulated between walking speed and 30 km / h in such a way that it was possible to stop in time in front of an obstacle (train). The signal was expressly only to be obeyed when visibility was good. As soon as the section of the route was free and the main signal was not disturbed, the system stopped the signals for travel terms. The signal continued to operate even after the operational test Ma-Signals was dismantled in 1959 and was also installed again in the new signal box in the main train station in 1975. In the event of a malfunction, additional replacement signals were installed that were not switched by the system. With the commissioning of the ESTW Köln Bbf 2014, the line between the main train station and the depot was converted into a station track with blocking signals and the caution signals were dismantled. The new design means that shunting runs are carried out in regular operation and therefore also on sight.

The signal was introduced across the board as signal Zs 7 on May 28, 1975 on the Bundesbahn.

On the main line of the Stuttgart S-Bahn , an automatically controlled warning signal was in operation from 1978 to 2010, which enabled entry into a blocked area on sight and thus a dense train sequence with a scheduled 24 trains per hour and direction. The operation of this signal was based on an exemption. The signal at the beginning of the S-Bahn ramp was activated automatically when both of the ramp's downtown tracks were free and the train in front had reached the platform. The signal was relocated due to construction work for the Stuttgart 21 project , which meant that the underlying special permit expired and the signal could no longer be operated. While this signal (and another signal at the start of the ramp) was taken out of service, other such caution signals are still in operation on the main route (as of 2016). They make it possible to follow suit at up to 30 km / h when the train in front has cleared a certain section of the route and has already occupied another.

On the Deutsche Reichsbahn, the signal had the designation Zs 11, but the same appearance. With the introduction of guideline 301 as a signal book to replace the DV 301, the designation was standardized to "Zs 7" with effect from December 14, 2008.

LZB, ETCS

The substitute signal can also be set up on "virtual" signals ( ETCS stop board , block identifier ).

In operation with ETCS Level 2 in Germany, if there is an active caution signal at the entry signal, permission to drive in On Sight (OS) mode is issued.

Individual evidence

  1. ↑ Deutsche Bahn AG: Guideline (Ril) 301 “Signalbuch”, module 301.0301 “Additional signals”, section 8, paragraph 1 as well as in the ESO
  2. ^ Deutsche Bahn AG: Ril 301, Module 301.0301, Section 8, Paragraph 2 as well as in the ESO
  3. ↑ Deutsche Bahn AG: Guideline 819 "Planning LST Systems", Module 819.9002 "Symbols for Safety Plans"
  4. ↑ Leaflet on the special features of the railway systems in the “Cologne area” dated May 6, 1959. Weblink
  5. ↑ Web link to old signal book
  6. ^ Stuttgart 21: S-Bahn chaos due to construction work , Eurailpress, message from July 1, 2010.
  7. ↑ Study on the introduction of ETCS in the core network of the Stuttgart S-Bahn. (PDF) Final report. WSP Infrastructure Engineering, NEXTRAIL, quattron management consulting, VIA Consulting & Development GmbH, Railistics, January 30, 2019, p. 85 f. , accessed April 26, 2019 .