Emergency brake override
The emergency brake override ( NBÜ ) is used on passenger trains to allow the train to continue driving despite the emergency brake being activated and to bring it to a standstill at a more suitable location. The reason for their introduction was that stopping a burning train in a tunnel can have devastating consequences, but also that a train that comes to a standstill at a point that is difficult to access makes recovery more difficult.
NBÜ at the railroad
In the case of railways , the emergency brake override only works with appropriately equipped passenger coaches and railcars . In addition, the motor vehicle must also be equipped accordingly and connected to the car via a corresponding control line via which the control signals are transmitted.
The emergency brake override must be used by the driver in specially marked sections of the route. As a rule, these are areas that are difficult to access for aid teams (tunnels, mountainsides, long bridges). In Germany and Austria , these areas can be recognized by the fact that there are orange-colored horizontal stripes at the top and bottom of the hectometer tables . If the train is on a section of the route marked in this way, the driver must bridge an emergency brake and continue to the first hectometer board without orange horizontal stripes. There he must stop the train in such a way that the train has left the NBÜ section.
The markings ( NBÜ mark ) are intended for tunnels more than 500 m long in Germany that are driven at more than 160 km / h. They show the driver in which sections of the route in front of and in the tunnel he has to take measures to bridge when the emergency brake is actuated. In these sections, kilometer and hectometer signs above and below are supplemented by an orange horizontal stripe. They should start on both sides of the fifth hectometer board in front of the tunnel and should be arranged along both sides of the route. The marking must continue until the fifth hectometer sign before the end of the tunnel. In the case of two consecutive tunnels less than 1000 m apart, the NBÜ sections merge.
In Switzerland, apart from under ETCS Level 2 , there is no special marking of the NBA / NBÜ sections. The effect of the emergency brake must be bridged in tunnels, on bridges or if the train would come to a standstill in these areas if the emergency brake were applied. The train must then be stopped at a suitable point.
Technical implementation
System DB
The "System DB" is an NBÜ system developed by the former Deutsche Bundesbahn itself. The actuation of an emergency brake leads to an immediate venting of the main air line, which can be bridged by the driver at a later date. In contrast to the NBÜ according to UIC 541-5, the 13 or 18-pin IS line according to UIC 558 , which was already available on the passenger coaches at that time, is used here as the transmission medium . A complex, expensive post-installation of separate additional 9-pin EBAS lines was not necessary. Due to the lack of free cores in the IS line, cores 9 to 12 had to be assigned several times. This later led to undesirable interactions between the NBÜ-DB and door control systems for regional transport vehicles such as SAT or TAV, which have since been further developed. DB Regio then decided to no longer use the NBÜ-DB system on their wagons in the future and developed the NBÜ system in 2004. The system will continue to be used on locomotive-hauled passenger trains for long-distance services by Deutsche Bahn and several other European railways.
The emergency brake override was one of four main requirements from an expert report submitted in 1983 to determine and increase safety on the first new German high-speed lines under construction. In the many tunnels on the first new high-speed rail lines, actuation of the emergency brake could increase the risk, as it could unintentionally stop a train in the tunnel. The braking effect of the emergency brake should therefore not be used on routes with a high proportion of tunnels. The emergency brake override was included in the Third EBO Amendment Ordinance in May 1991 in the Railway Construction and Operating Regulations (EBO).
UIC 541-5
A standardization set by the UIC provides for UIC 541-5 for the ep brake control and thus also for the NBÜ. A separate 9-pin cable (EBAS cable, electronic brake query and control system) is used for this. In this system, too, the main air line is initially vented immediately when the emergency brake is actuated until it is bridged.
NBÜ 2004
This system also uses the EBAS line according to UIC 541-5, however, the actuation of an emergency brake initially only leads to a visual and acoustic message in the driver's cab. The driver must confirm this message either by means of a bridging order or by emergency braking. Otherwise the emergency braking will take effect automatically after a short time. Emergency braking when the train is stationary or shortly after departure cannot be bridged. Since July 1, 2011, NBÜ 2004 has been the NBÜ system approved by the Federal Railway Authority for DB regional trains.
The system was further developed from the point of view of system monitoring and reliability. By the end of 2014, the NBÜ 2004 systems had to be upgraded to "NBÜ 2004 optimized", after which the approval for the NBÜ 2004 was no longer applicable.
The optimization essentially consists of a second contact on the emergency brake boxes. The switching of the contacts is changed. One contact is read from the NBÜ card of the car and processed, the other contact acts directly on the NBÜ release loop of the 9-pin cabling. This means that even with a car without its own power supply, e.g. B. if the battery is defective, the emergency brake can be triggered.
In Switzerland, this system is known as the emergency braking requirement (NBA) .
NBÜ in multiple units
Multiple units with a central buffer coupling are not so restricted in terms of the number of control lines that are also coupled, and they can usually only be coupled with their own series or a limited series of series. These trains use their own NBÜ solution. This is based on the already existing ep brake. The train control device evaluates the signals and implements the NBÜ function in the software in the communication with the brake computer. The behavior and scope of functions correspond to the NBÜ 2004 or the NBÜ according to UIC 541-5.
NBÜ in city traffic
In public transport is the emergency brake, especially in subways , but also in underground trains running commuter trains in use. Here, too, it is usually a better strategy to continue the train in an emergency (e.g. in the event of a fire in the train) to the next station, on the one hand to enable passengers to leave the danger area quickly and on the other hand to facilitate access for the auxiliary staff. As a rule, the alarm lever only acts as an emergency brake until shortly after the journey (in Germany usually 10 seconds), otherwise a voice connection is established with the train driver or the driver.
The S-Bahn-NBÜ reflected application cases in which driving the vehicle on is more likely to be the more appropriate response. This applies to routes with a high proportion of tunnels, elevated railways, etc. In general, this type of NBÜ is out of date, as the newer NBÜ2004 according to regulation B009 NBÜ Rev 3.1 with the two nested state machines also covers this application, but stops the vehicle if the driver fails to react.
On September 12, 2015, a class 425 multiple unit equipped with S-Bahn-NBÜ ran through several stations on the Elsenz Valley Railway without stopping. The driver had become incapacitated, but the safety driving circuit did not trigger an emergency brake. The emergency brake operated by passengers only caused an alarm signal in the driver's cab, to which the driver did not react. A similar incident occurred on December 22, 2019 in a vehicle of the Bonn Stadtbahn .
The emergency brake override was introduced in the underground trains of the Berliner Verkehrsbetriebe (BVG) in 1988 as a reaction to the fire in King's Cross St. Pancras station .
See also
Individual evidence
- ↑ David Selmer: Attach kilometer, hectometer and additional symbols . Directive 800.0104. Deutsche Bahn February 17, 2020, p. 1, 4 .
- ↑ Deutsche Bundesbahn, Central Office Munich (ed.): Safety concept for the tunnels of the new lines. Final report . November 1983, cover sheet and pp. 1, 93.
- ^ Hans-Heinrich Grauf: The emergency brake concept for new lines . In: The Federal Railroad . tape 64 , no. 8 , August 1988, ISSN 0007-5876 , pp. 709-712 .
- ↑ Fritz Pätzold, Klaus-Dieter Wittenberg: The Third Ordinance to Change the Railway Construction and Operating Regulations (EBO) . In: The Federal Railroad . No. 7-8 , 1991, ISSN 0007-5876 , pp. 759-770 .
- ↑ Regulation B009 NBÜ Rev 3.1 (PDF) Federal Railway Office. May 22, 2005. Retrieved September 15, 2019.
- ↑ Günther Keller: During the S-Bahn ride through the Elsenz Valley, the driver passed out. Rhein-Neckar-Zeitung, September 18, 2015, accessed on September 18, 2015 .
- ↑ Unauthorized train movement other than SPAD, 12-09-15, Hoffenheim - Reilsheim (Germany). European Railway Agency , accessed August 30, 2019 .
- ^ Dietrich Sondermann: Passengers stop driverless trams in Bonn. WDR, accessed December 22, 2019 .
- ↑ BVG considers a similar accident in Berlin to be ruled out. In: Tagesspiegel , November 1987
