The route block , also called route block , is a system for securing train journeys on the open route. By logically blocking individual route sections for the following train, it ensures that several trains run together on one track at a fixed distance from the train in front. In addition, he can - if he is set up for this - protect these train journeys from oncoming journeys . This statically or dynamically determined distance is sensed by fixed technical equipment and signaled to the train according to a location-related and a train-related logic.
Under certain conditions, the route block can also be used within train stations. As a rule, however , the signal dependency in train stations is guaranteed by the route security, the train station block only serves to create dependencies between mechanical signal boxes within a train station.
The first non-automatic block device was invented by William Fothergill Cooke and was first used in 1844 on the Norwich-Yarmouth route of the Great Eastern Railway . The signs were given with a needle pointing to the right or left according to the direction of travel of the train. Block movements with mechanical dependence on the main signals only existed since 1874 .
Because of the great importance of driving at a distance for the safety of rail operations, a legal basis was created in Germany as early as 1928 in the Railway Construction and Operating Regulations (EBO), which is binding for all regular-gauge public transport railways. It demands that the signal for the journey into a block section on main lines with a particularly dense train sequence must be locked to the next train sequence point . On the German railways, not only the main lines, but also many branch lines on which passenger trains run, are equipped with route blocks.
While driving in the space distance was initially only ensured by messages between the interlockings involved in the so-called train notification procedure , the route block creates technical dependencies and constraints that ensure that there is always only one train in a block section. The main signal at the beginning of the block section is held in the stop position under block lock until it is established that the train ahead has left this block section including the protective section behind it and is covered by a signal indicating a stop. On single-track lines and double track lines with track change operation of the block system provides also for the exclusion of counter trips . This is done by changing the permit . Only the end of the block where the permit is located can trains enter the section. The permit can only be changed if the entire block route to the next block end point is free of train journeys. Operating points that serve exclusively to regulate the sequence of trains are called block points .
Signal box technology
With the further development of interlocking technology from mechanical to electronic interlocking in connection with the operating centers of Deutsche Bahn AG, which are still under construction , the route block was also continuously developed. Essentially, two basic designs of the section block are still in use in Germany today, but in a large number of different variants:
- Non -automatic section block as a mechanical field block in mechanical and electromechanical interlockings , manually operated relay block or semi-automatic (only bloom function) train-operated relay block in electromechanical interlockings, partly also in relay interlockings and electronic interlockings , as well as carrier frequency block .
- Automatic section block mostly in relay and electronic interlockings .
In practice, each section block can be adapted to any type of interlocking. The only thing that matters is what is economically reasonable and appropriate to the route.
All modern railway systems adhere to the principle of spatial distance due to the physics of the braking processes. Outside the UIC , various railway administrations have succeeded in significantly improving the performance of the track network without compromising operational safety. The state-of-the-art rigid block lock from 1928 is being resolved by the introduction of modern, high-tensile safety components and the complementary separation of the fixed-track and high-tensile safety systems.
With the separation of the safety systems, it is possible to run trains safely at an electrical point of view and thus to increase the performance of the correspondingly operated railway lines. The introduction of such modern system concepts is planned for Europe with ETCS . With ETCS Level 3 , the completeness of the trains is to be reliably detected on the vehicle side and track-side track vacancy detection is to be largely dispensed with. The main obstacle is the lack of a general automatic train completeness check .
Before a train can enter a block section, the following conditions must be met:
- The block section must be free
- The danger point distance behind the signal at the end of the block section must be clear
- The train in front must be covered by a stop signal
Only when these conditions are met can the block or exit signal at the beginning of a block section be set to travel.
After a train has entered the block section, it is blocked for other train journeys by the bloom . Pre-blocking can only take place when the exit or block signal has indicated a travel concept and returns to the stop position. This process blocks the exit signal or block signal at the beginning of the block section until the back block has been received. This is a result underride protection guaranteed.
After the block section has been cleared, the block or entry signal of the next station at the end of the block section is reset to stop and the train is blocked back there ( back block). The stop position of the following signal and the cooperation of the train is a technical prerequisite for blocking back, because the train is only protected from a following train under the "cover" of this signal. Blocking back removes the blocking of the signal at the beginning of the block section.
To prevent an exit or block signal from being set to travel several times without block operation, there is a route repetition lock . This ensures that a signal can only be set to speed again after the front block and the subsequent back block have been operated.
The prerequisite for the change of permit is that the entire block route between the block end points is free of journeys. In the case of non-automatic field and relay blocks, the initial position of the start fields of the end of the block and of the block positions in between is evaluated. In order to prevent this situation from occurring incorrectly because a block attendant blocks back but fails to block forward, block sections on routes with a change of permit receive coupling buttons. Forward and backward blocks are only possible at the same time.
Depending on whether the back block information is transmitted once or continuously, a distinction is made between non-automatic or automatic section blocks:
With all variants of the non-automatic section block without track vacancy detection system, the operator of the end field must ensure that a train with a train end signal has passed the locally defined signal train termination point before the train can be blocked back. There is also the possibility that another company railroader sends a train termination message to the operator of the route block. Only then is it certain that the train has arrived in full and has cleared the block section including the following protective section. Even today there is still no alternative to this relatively cumbersome process on routes with a mechanical field block and manually operated relay block. The information as to whether a train has completely left the block section is only available at certain points (at the time of blocking back).
In contrast to this, with the automatic route block, the conditions for the approval of the next train journey are constantly checked with the help of a track vacancy detection system .
Non-automatic route block
The field block is the oldest form of the section block. Only AC block fields are used for the section block .
In the basic position, the exit signal (s) can be set in the direction of the route, on routes with a change of permit only at the end of the block on which the permit is located. The beginning field is unlocked, the end field is blocked. The permission field is unblocked if permission is given. Only the permission field for issuing a permit can be blocked in this situation. Blocking the initial field is prevented by the mechanical key lock as part of the initial lock. The entry signal, on the other hand, can always be set on the section block side, the end lock prevents this signal from being operated only during the return block release.
When the exit signal is pulled, the mechanical key lock of the starting field becomes ineffective and the route repetition lock is prepared. The signal lock of the initial lock continues to prevent blocking as long as the exit signal is on. When the exit signal lever is reset to the stop position, the route repetition lock is activated, the mechanical key lock is still ineffective and the starting field can be blocked. This prepares the resetting of the route repetition lock, the locking of the exit signals in the direction of the route is done by the signal lock of the initial lock. The corresponding end field at the end of the block section is unblocked. Further changes do not occur for the time being, the immediate blocking back is prevented by the electrical route key lock above the end field. It triggers when the train has entered and cleared a tension point behind the entry signal (usually an insulated rail in connection with a rail contact ). This makes the end field operable. This train action forces the train to cooperate, but it does not contain any information about the completeness of this train. After the operator has determined the evacuation of the block section at the end of this block section by observing the end of the train, he sets the signal back to stop at the end of the block section and blocks the end field ( block back ). The starting field is unblocked, the route repetition lock is reset, the signals at the beginning of the block section are released again and the next trip can follow.
In the case of single-track routes, the permission field is added to prevent oncoming journeys . Only the train station that has the permit can set an exit signal to drive and thus allow journeys into the block section. The exit signals of the other station are blocked during this time. So that journeys can take place in the opposite direction, the permit must be changed by blocking the permit field. This design for single-track routes is called (three-field) route block form C. Permission fields are only available at the block end points ( train reporting points ), where trains can cross and the train sequence can be changed. On train sequence locations , such as B. Block positions, however, only start and end fields are available. The form C section block requires six cable cores for floating connection between two block end points, and nine if there are block sections on sections with a change of permit.
In the field block, block locks establish the connection of the block fields to the mechanical interlocking and lock the signals there:
- The start lock blocks the signal levers of the block or exit signals after the start field has been blocked. The repetition lock is also integrated in the initial lock, which prevents the exit signals from being set to travel again without having to press the block in the meantime.
- The end lock , also called back block lock , prevents back blocking as long as the entry or block signal is on.
- The permit block, which is connected to the route repetition block by a transmission tab in most types of mechanical interlockings, blocks the exit signals in the direction of the route when the permit field is blocked, and also prevents the permit field from being blocked when the exit signal is in motion and then when the route repeat block is applied or the start field is blocked and thus the issuing of a permit. It requires the installation of the permission field to the right of the starting field. If this is not possible because this space is not available (because, for example, a line was double-tracked when the signal box was built and was only subsequently dismantled to single-track operation), then the function of the permit lock is electric with an electric key lock above the start and Permission field reproduced.
The field block was also used in older electromechanical interlockings, in some cases also in relay interlockings. However, the non-existent mechanical dependencies of the block locks must be reproduced by electrical dependencies (so-called lock - free block ). The block box of the field block was set up next to the lever system. The use of light signals in mechanical interlockings with button control (especially exit signals) also requires the switch to the block without locks.
Since the sequence of operation of the start and end field (each in different interlockings) is specified in the field block, this is not suitable for securing train journeys that end and turn between the interlockings. For this reason, the field block is not suitable for making two signal boxes within a station dependent. This led to the development of the station block .
In the later electromechanical signal boxes, the block box of the field block was perceived as a nuisance, which is why the relay block was developed at the end of the 1930s. This was initially called a magnetic switch block.
The relay block works in principle like the field block and is also compatible with it. Instead of block fields, however, block relays (stepping devices with a polarized magnet system) are used. Initially, the section block fields were replaced one-to-one by block relays ( three-field relay block ), due to the similar blocking function (in the blocked position, the exit signals are locked in the stop position) around 1960, the start and permit block relay was combined in a common block relay (A / Erl) . The end field, which has no locking function, has been replaced by a flat relay. This created the single-field relay block . The selection element is the route repetition block, usually a backup relay. If it is in the basic position, the permit is issued, in the active position the bloom.
The manually operated relay block is blocked forwards and backwards as with the field block by the operator. In the case of electromechanical interlockings, the blocking button in the lever assembly is usually used to pre-block. To do this, the route signal lever must first be turned over and back, the exit signal must be on hold and the train must have participated. It is only possible to block back manually after the bloom has arrived, the entry signal is on hold, the train has participated and the train has been closed.
The semi-automatic relay block is often used in relay interlockings, and also in modernized mechanical or electromechanical interlockings with light signals . Displays and control buttons are integrated in the track diagram table. The bloom takes place automatically when driving on the train action for the route clearance, but it must be blocked back manually after the end of the train has been recognized. If a track vacancy detection system is available or the completeness of the trains can be reliably determined in another way, it is also possible to set up the automatic back block (automated relay block) . However, the automated relay block is still one of the non-automatic block systems, because the operator can check the track section and block it back if the track vacancy detection system malfunctions. With the relay block it is possible to set up a manual auxiliary bloom . This means that block operation is still possible if, for example , trains have to run without exit signal operation or on a substitute signal in the event of a fault . This auxiliary block was then also introduced for the block-free field block. When it is activated, the route repetition lock is activated and the electrical key lock above the start field ( blue key lock ) is triggered.
The relay block is still used today as an interface between electronic and other types of signal boxes.
In the field and relay block, the energy required to initiate the blocking process in the neighboring interlocking is completely routed via the block wires (which are usually routed together with the communication lines in the route (telecommunication) cable, in the past on routes without alternating current electrification also via overhead lines) transfer. The energy losses on these lines limit the maximum distance between two signal boxes, which became a problem in the 1970s, when the Deutsche Bundesbahn dismantled more and more stations to stopping points and thus the block sections became longer and longer. In addition, the field or relay block requires up to nine wires between the stations for single-track routes. However, there are also relay block designs that only require two wires per track (so-called two-wire block). However, they are not compatible with each other, require the same equipment for a route between two block end points and have remained comparatively rare.
Carrier frequency block
In the 1970s, several serious accidents ( railway accident in Warngau and railway accident in Dahlerau ) occurred on branch lines without a line block , which forced the Federal Railways at that time to retrofit line blocks on these lines. However, the mechanical interlockings used could only have been retrofitted with a field block with great effort.
All these reasons led to the development of the carrier frequency block 71 ( Tf block 71 ), which works in a similar way to the field or relay block. The block processes are carried out electronically, however, by modulating the carrier frequency sent on a pair of line telecommunication wires depending on the information (pre-block, back-block, permission and direction of travel) and evaluating it on the receiving end. The electronically received information was converted into blocking information for the interlocking by means of relay switching. Blocking is usually done automatically by the train. The back block is done by the operator. Backblocking could also be automated with an additional axle counting device.
By using an existing pair of telecommunication wires, a cost-effective retrofit solution for branch lines could be developed.
Branch line block
This term describes a block protection of a branch line: For each train entering the branch line, the block section is blocked for other train journeys by pre-blocking. After the train arrives, the section is unblocked again by blocking back so that another train can enter the branch line. The branch line block is therefore a special form of the non-automatic line block in which all block facilities are located at one operating point.
Automatic route block
In the case of an automatic route block, the trains are no longer blocked forwards and backwards. Instead, the technology ensures the following conditions as long as a block signal is in motion:
- The track vacancy detection system reports that the block section and the danger point distance are clear,
- The following main signal, which protects the following block section, was in the stop position at a point in time after the last train had passed, but - depending on the design of the section block - can meanwhile be moving again
In contrast to the non-automatic route block, the prerequisites for the approval of a train journey are checked continuously, i.e. especially after the signal has been set.
A distinction is made between different variants of the automatic route block.
With self-blocking, train journeys are secured automatically or automatically by train-operated block devices. Auto-block systems were created after the invention of the track circuit made it possible to provide complete and safe automatic track vacancy detection, initially on densely occupied urban rapid transit lines at the beginning of the twentieth century . This made it possible to shorten the block sections without additional personnel expenditure except for the braking distance, if there is a multi-section signaling also below this and the train headway times to under two minutes. The track vacancy detection system automatically blocks the signals from an occupied block section. Early designs, for example the AB 28 and AB 37 used on the Berlin S-Bahn, did not allow a change of permit, they could only be used on double-track routes. The change of permit only became available after the Second World War, initially without block signals against the normal direction of travel. With newer designs it is possible to set up no, fewer or as many block signals as in the normal direction of travel. It is also possible to waive the change of permit. The undisturbed automatic section block returns to the basic position even after driving against the set direction of travel.
Will block signals used, they are in permission direction in the basic position to drive (except when they cover crossings). When driving on the section behind a block signal, it automatically falls into the stop position and then remains initially blocked. This also happens if the busy message is the result of a fault. A malfunction always has the safer side. After the block section and the associated protective section behind the next block signal have been cleared, the block signal automatically returns to the basic position when the following main signal has assumed the stop position. These block signals are called automatic block signals or self-block signals ( Sbk ). Entry and exit signals from the stations delimiting the section are included in the dependencies.
The most widespread design of the self-block in the area of the Deutsche Bundesbahn is the Sb 60 . In the area of the Deutsche Reichsbahn was called this form of automatic track block automatic block or automatic block . There was the most developed design of the AB 70 with standardized switch frames and cabinets for almost every application.
The signaling against the set permission direction is different. While the block signals in Germany show the concept of stop in this case, in many other countries they are darkened, with the last block signal in front of a train station in the warning position. This facilitates journeys in the opposite direction to the permit, in particular in the event of a malfunction, as the driver only has to be instructed once to drive past a signal indicating a stop.
In more modern relay interlockings and electronic interlockings (ESTW), the section block is often controlled centrally from the interlocking (central block). The first design of this type was the central block 65 from Siemens. The centralization of the relay assemblies in the interlocking was advantageous here, which should reduce the maintenance and troubleshooting effort. The distance of the block signals from the interlocking is limited to 6.5 km when using conventional cables. With fiber optic technology, however, this limit has in fact been lifted nowadays. However, it requires an additional and uninterruptible power supply for each block signal integrated in this way.
A part or all of the free route between two operating points is assigned to an interlocking. In the basic position, the signals are on stop. When a route is set in a track, the block signals are "triggered", i. H. if the section of the train route is free and a "return report" is received, the signal goes on. If it is occupied, the trigger is saved and the signal goes into motion once the conditions have been met ("coasting"). Thus, the trains automatically follow each other in the shortest possible block distance. In addition, level crossing dependencies can be set up, i. H. the block signals also cover the level crossings and only start moving when the level crossing system is secured. The level crossing can be checked for freedom by looking (also via a camera) or automatically using a radar scanner. In order to keep the level crossing closing times as short as possible, these signals only start moving shortly before the calculated passage of the train past the distant signal. There are also track switching devices that announce the train's passage and ensure that the level crossing system is switched on.
Technically, these are so-called block routes, which are similar to train station routes.
LZB central block
The main signals can only come into the driving position if all following block sections are free until the next main signal. LZB -controlled trains, on the other hand, can use electronic displays in the driver's cab to follow a train ahead - regardless of whether this is LZB-guided or signal-guided - at a distance from the LZB block points (so-called partial blocks). The train has to pass a signal that actually indicates a stop. In order not to irritate the train driver, the signal before the train enters the sub-block before the signal blanked .
High performance block
The high-performance block based on liner train control is a component of CIR-ELKE for increasing the performance of heavily used train routes with distinct mixed traffic from trains of different speeds. A clever arrangement of LZB block locations on the open route as well as partial train routes within train stations should make overtaking processes more fluid. The following measures are taken:
- Shorter LZB block sections on the open road.
- Significantly shorter LZB block sections in front of compulsory points such as train stations and crossing and branching points than in the middle of the route. This allows a faster train to run closer to a slower train in front of a train station, which speeds up the overtaking process.
- After train stations there are also significantly shorter LZB block sections. In this way, an overtaken train is more likely to follow the overtaking one.
- Use of partial train routes in stations for LZB-guided trains. These can then move closer to the train in front within stations.
- Independent determination of the permitted speeds in train stations and junctions by the LZB. This means that trains entering a passing track or a branch line do not have to brake to the lower speed at the entry signal , but must have reached the lower speed shortly before the first branching point.
- Higher speeds, especially for freight trains with LZB guidance, by eliminating the rigid braking distance of 1000 meters.
In this way, the capacity of the lines is to be increased by 20% to 30%. The high-performance block requires all trains to be equipped with LZB for effective use of the advantages.
High performance block can also be formed with ETCS . In Germany, block sections of up to 100 meters can be implemented with ETCS; a change to the ETCS specifications for further shortening to 30 m is in progress (as of January 2019). In the course of the digital node Stuttgart , partial blocks on the platform in train stations are to be developed with ETCS.
There are various restrictions for the high-performance block. Block labels may not be placed less than 300 m in front of a distant signal and not between the start and finish of shunting routes . Furthermore, no stand- alone speed indicators are allowed in train routes divided by block markings .
Length of the block sections
The free route secured by the route block is divided into individual train sequence sections , also block sections. The length of the block sections is determined by the train density, the permissible speed and the length of the trains. A classic block section must be at least long enough that a train can safely stop after the advance warning of the main signal to stop by the distant signal in the warning position, in modern systems by the distant main signal from the permitted line speed. In Germany, this braking distance on the line is 700, 1000 or 1300 meters on main lines and 400 or 700 meters on secondary lines, depending on the maximum permitted speed.
To shorten the block distances , the H / V signal system uses the half-rule distance method , in which the minimum distance between two block signals is halved. A main signal continues to be announced in the braking distance, that is to say over two subsequent sections; the signal in between shows a repetition of the last (distant signal) image with additional light, because from here only a shortened braking distance is available, and an additional identification light on the main signal screen.
In the case of Hl and Ks signals, on the other hand, the braking distance can be specified in response to a main signal indicating a stop over several block sections using ever lower speed specifications (with Ks signals by additional signals) (»signals in the shortened braking distance«). A characteristic of this arrangement is that when the following signals are released, the signaled speed at the location of the main signals is also upgraded, for example by extinguishing yellow 2 (possibly in connection with light strips) or Zs 3 .
A further increase in capacity is possible by driving in a moving distance .
Particular attention should be paid to the route block when small cars are driving that incorrectly affect the systems or other irregularities such as technical malfunctions . The dispatchers work according to a dedicated set of rules to maintain operational safety regardless of technical security.
Small car journeys were particularly problematic as long as train effects were actuated by rail current closers, which evaluate the rail deflection caused by a wheel rolling over it. The low axle travel mass was not sufficient for a safe release. This is why small cars that were supposed to go on the open road ran on special driving instructions and thus without signal operation. After rail current closers are hardly used any more, at least in the main line network, the corresponding regulations could be repealed.
In the classic route block, the most common malfunction is the failure of the route key lock due to the failure of the pull, the corresponding device in the relay block is the back block unlocker. This means that blocking back is not possible and the next train must run without signal operation and therefore on special order by means of a substitute signal or a written command . In the case of routes with a change of permit, it is no longer possible to issue permits, so trains are affected in both directions. The dispatchers involved introduce the feedback to ensure driving in the distance . Auxiliary resolutions to circumvent this disruption were abolished in Germany after their improper use led to serious accidents.
If trains have to take place without an exit signal condition, pre-blocking is not possible. The route key lock at the end of the block section is triggered during this trip, although no pre-block has been received. This would make it possible to block back the next train immediately after the block. For this reason, feedback must also be introduced when trains are running without an exit signal control. In the case of designs without mechanical dependency between the signal operating device and the section block, which applies to all forms of the relay, automatic and central block as well as the block-free field block, in this case the auxiliary block key can be used to pre-block.
If trains have to pass the stop-indicating entry or interlocking operated block signals, then the pull action for the electrical route key lock or the back block release is not switched on. In order to prevent disruptions in a train station from affecting the route, there is a switch for this case . If you press it, which requires proof, the route key lock is triggered when the train is driven on and blocking back is possible.
In the case of automatic line block designs, malfunctions in the automatic track vacancy detection system in particular have such an effect that one or more block signals do not reach the travel position. This can also affect exit signals from train stations. Such disruptions are problematic on routes with large parking areas on which there is no point that can determine the completeness of a train. In the worst case, the driver has to do this himself during an operational stop.
Application of the principle to roller coasters
Unlike most other rail vehicles, roller coasters usually do not have their own drive or braking system (exceptions: powered coasters , “powered roller coasters” and some old wooden roller coasters (scenic railways) ). That is why braking and drive systems mounted on or next to the track are used on roller coasters.
On systems with long distances or with vehicles for a few people, several vehicles usually drive at the same time to increase passenger capacity. In order to avoid collisions, the route is then divided into several block sections depending on the number of vehicles. These are separated from each other by section elements that enable a defined stop (brakes or drive elements). A vehicle is held until the vehicle in front has completely left the following block section. In order to check this, sensors - various types of proximity switches are used - are attached to the track, which inform the central controller of the roller coaster. As soon as the block is free, the brake is released or the transport system is released.
Electric Tablet System describes British block security technology.
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