71-778: 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. The German Linienzugbeeinflussung translates to continuous train control , literally: linear train influencing . It
142-400: A "response telegram" at 600 bits per second at 56 kHz ± 0.2 kHz. Call telegrams are 83.5 bits long: One might note that there is no "train identification" field in the telegram. Instead, a train is identified by position. See Zones and Addressing for more details. There are 4 types of response telegrams, each 41 bits long. The exact type of telegram a train sends depends on
213-439: 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
284-404: A buzzer and display the distance to and speed of the restriction. As the train continues the target distance will decrease. As the train nears the speed restriction the permitted speed will start to decrease, ending up at the target speed at the restriction. At that point the display will change to the next target. The LZB system treats a red signal or the beginning of a block containing a train as
355-426: A de facto national standard, and most installations of cab signals in the current era have been this type. Recently, there have been several new types of cab signalling which use communications-based technology to reduce the cost of wayside equipment or supplement existing signal technologies to enforce speed restrictions and absolute stops and to respond to grade crossing malfunctions or incursions. The first of these
426-413: A few modifications. All cab signalling systems must have a continuous in-cab indication to inform the driver of track condition ahead; however, these fall into two main categories. Intermittent cab signals are updated at discrete points along the rail line and between these points the display will reflect information from the last update. Continuous cab signals receive a continuous flow of information about
497-412: A full-screen computer generated "Man-machine interface" (MMI) display rather than the separate dials of the "Modular cab display" (MFA). LZB operates by exchanging telegrams between the central controller and the trains. The central controller transmits a "call telegram" using Frequency-shift keying (FSK) signalling at 1200 bits per second on a 36 kHz ± 0.4 kHz. The train replies with
568-502: A larger number of information points that may have been possible with older systems as well as finer grained signalling information. The British Automatic Train Protection was one example of this technology along with the more recent Dutch ATB-NG. Wireless cab signalling systems dispense with all track-based communications infrastructure and instead rely on fixed wireless transmitters to send trains signalling information. This method
639-417: A magnetic field. Inductive systems are non-contact systems that rely on more than the simple presence or absence of a magnetic field to transmit a message. Inductive systems typically require a beacon or an induction loop to be installed at every signal and other intermediate locations. The inductive coil uses a changing magnetic field to transmit messages to the train. Typically, the frequency of pulses in
710-408: A means of transmitting information from wayside to train. There are a few main methods to accomplish this information transfer. This is popular for early intermittent systems that used the presence of a magnetic field or electric current to designate a hazardous condition. The British Rail Automatic Warning System (AWS) is an example of a two-indication cab signal system transmitting information using
781-441: A more comprehensive train protection system that can automatically apply the brakes stopping the train if the operator does not respond appropriately to a dangerous condition. The main purpose of a signal system is to enforce a safe separation between trains and to stop or slow trains in advance of a restrictive situation. The cab signal system is an improvement over the wayside signal system, where visual signals beside or above
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#1732773201315852-478: A new "change of section identification" telegram and gets a new address. Until the train knows its address it will ignore any telegrams received. Thus, if a train doesn't properly enter into the controlled section it won't be under LZB control until the next section. The main task of LZB is signalling to the train the speed and distance it is allowed to travel. It does this by transmitting periodic call telegrams to each train one to five times per second, depending on
923-684: A speed restriction of 0 speed. The driver will see the same sequence as approaching a speed restriction except the target speed is 0. LZB includes Automatic Train Protection . If the driver exceeds the permitted speed plus a margin LZB will activate the buzzer and an overspeed light. If the driver fails to slow the train the LZB system can apply the brakes itself, bringing the train to a halt if necessary. LZB also includes an Automatic Train Operation system known as AFB (Automatische Fahr- und Bremssteuerung, automatic driving and braking control), which enables
994-480: A stopping point, the monitoring speed follows a braking curve similar to the permitted speed, but with a higher deceleration, that will bring it to zero at the stopping point. When approaching a speed restriction, the monitoring speed braking curve intersects the speed restriction point at 8.75 km/h (5.44 mph) above the constant speed. Cab signalling Cab signaling is a railway safety system that communicates track status and condition information to
1065-438: A train is approaching a speed restriction the control centre will transmit a packet with an XG location set to a point behind the speed restriction such that a train, decelerating based on its braking curve, will arrive at the correct speed at the start of the speed restriction. This, as well as deceleration to zero speed, is illustrated with the green line in the "Permitted and supervised speed calculation" figure. The red line in
1136-780: Is also called linienförmige Zugbeeinflussung . LZB is deprecated and will be replaced with 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
1207-427: Is essentially an inductive system that uses the running rails as information transmitter. The coded track circuits serve a dual purpose: to perform the train detection and rail continuity detection functions of a standard track circuit , and to continuously transmit signal indications to the train. The coded track circuit systems eliminate the need for specialized beacons. Examples of coded track circuit systems include
1278-638: Is most closely associated with communications-based train control . ETCS levels 2 and 3 make use of this system, as do a number of other cab signalling systems under development. The cab display unit (CDU), (also called a driver machine interface (DMI) in the ERTMS standard) is the interface between the train operator and the cab signalling system. Early CDU's displayed simple warning indications or representations of wayside railway signals. Later, many railways and rapid transit systems would dispense with miniature in-cab signals in favour of an indication of what speed
1349-551: The Santa Fe and New York Central , fulfilled the requirement by installing intermittent inductive train stop devices, the PRR saw an opportunity to improve operational efficiency and installed the first continuous cab signal systems, eventually settling on pulse code cab signaling technology supplied by Union Switch and Signal . In response to the PRR lead, the ICC mandated that some of
1420-573: The Austrian railways introduced LZB into their systems, and with the 23 May 1993 timetable change introduced EuroCity trains running 200 km/h (120 mph) on a 25 km (16 mi)-long section of the Westbahn between Linz and Wels . Siemens continued to develop the system, with "Computer Integrated Railroading", or "CIR ELKE", lineside equipment in 1999. This permitted shorter blocks and allowed speed restrictions for switches to start at
1491-672: The Pennsylvania Railroad (PRR) and Union Switch & Signal (US&S) became the de facto national standard. Variations of this system are also in use on many rapid transit systems and form the basis for several international cab signalling systems such as CAWS in Ireland, BACC in Italy, ALSN in Russia and the first generation Shinkansen signalling developed by Japan National Railways ( JNR ). In Europe and elsewhere in
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#17327732013151562-487: The Pennsylvania Railroad standard system , a variation of which was used on the London Underground Victoria line , Later, audio frequency (AF) track circuit systems eventually came to replace "power" frequency systems in rapid transit applications as higher frequency signals could self- attenuate reducing the need for insulated rail joints. Some of the first users of AF cab signal systems include
1633-530: The Washington Metro and Bay Area Rapid Transit . More recently, digital systems have become preferred, transmitting speed information to trains using datagrams instead of simple codes. The French TVM makes use of the running rails to transmit the digital signalling information, while the German LZB system makes use of auxiliary wires strung down the centre of the track to continually transmit
1704-435: The cab, crew compartment or driver's compartment of a locomotive , railcar or multiple unit . The information is continually updated giving an easy to read display to the train driver or engine driver . The simplest systems display the trackside signal, while more sophisticated systems also display allowable speed, location of nearby trains, and dynamic information about the track ahead. Cab signals can also be part of
1775-399: The "Group identity" in the call telegram. The most common type of telegram is type 1, which is used to signal a train's position and speed to the central controller. It contains the following fields: {LZB p3} The other telegrams are used primarily when a train enters the LZB controlled section. They all start with the same synchronization and start sequence and a "group identity" to identify
1846-474: The "Ü" light to indicate that LZB is running. From that point on the train's location is used to identify a train. When a train enters a new zone it sends a response telegram with the "vehicle location acknowledgement" filed indicating that it has advanced into a new zone. The central controller will then use the new zone when addressing the train in the future. Thus a trains address will gradually increase or decrease, depending on its direction, as it travels along
1917-489: The Fulda-Würzburg segment that started operation in 1988, it incorporated LZB into the lines. The lines were divided into blocks about 1.5 to 2.5 km (0.93 to 1.55 mi) long, but instead of having a signal for every block, there are only fixed signals at switches and stations, with approximately 7 km (4.3 mi) between them. If there was no train for the entire distance the entry signal would be green. If
1988-786: The PRR. These railways included the Central Railroad of New Jersey (installed on its Southern Division), the Reading Railroad (installed on its Atlantic City Railroad main line), the New York Central, and the Florida East Coast . Both the Chicago and North Western and Illinois Central employed a two-aspect system on select suburban lines near Chicago. The cab signals would display "Clear" or "Restricting" aspects. The CNW went further and eliminated
2059-514: The computer-based LZB L72 central controllers and equipped other lines with them. By the late 1970s, with the development of microprocessors, the 2-out-of-3 computers could be applied to on-board equipment. Siemens and SEL jointly developed the LZB 80 on-board system and equipped all locomotives and trains that travel over 160 km/h (99 mph) plus some heavy haul locomotives. By 1991, Germany replaced all LZB 100 equipment with LZB 80/L 72. When Germany built its high-speed lines, beginning with
2130-410: The continuous event relied upon by the cab signalling system. Early systems use the rails or loop conductors laid along the track to provide continuous communication between wayside signal systems and the train. These systems provided for the transmission of more information than was typically possible with contemporary intermittent systems and are what enabled the ability to display a miniature signal to
2201-417: The crossing the signal phase angle is changed by 180° reducing electrical interference between the track and the train as well as long-distance radiation of the signal. The train detects this crossing and uses it to help determine its position. Longer loops are generally fed from the middle rather than an end. One disadvantage of very long loops is that any break in the cable will disable LZB transmission for
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2272-412: The current speed. Digital cab signalling systems that make use of datagrams with "distance to target" information can use simple displays that simply inform the driver when they are approaching a speed penalty or have triggered a speed penalty or more complex ones that show a moving graph of the minimum braking curves permitted to reach the speed target. CDU's also inform the operator which, if any, mode
2343-431: The distance between the main and distant signal. But, this would require longer blocks, which would decrease line capacity for slower trains. Another solution would be to introduce multiple aspect signalling. A train travelling at 200 km/h (120 mph) would see a "slow to 160" signal in the first block and then a stop signal in the 2nd block. Introducing multi-aspect signalling would require substantial reworking for
2414-485: The driver to let the computer drive the train on auto-pilot, automatically driving at the maximum speed currently allowed by the LZB. In this mode, the driver only monitors the train and watches for unexpected obstacles on the tracks. Finally, the LZB vehicle system includes the conventional Indusi (or PZB) train protection system for use on lines not equipped with LZB. In the 1960s, the German railways wanted to increase
2485-466: The driver; hence the term, "cab signalling". Continuous systems are also more easily paired with Automatic Train Control technology, which can enforce speed restrictions based on information received through the signalling system, because continuous cab signals can change at any time to be more or less restrictive, providing for more efficient operation than intermittent ATC systems. Cab signals require
2556-642: The engineer a chance to decelerate. SES is in the process of being removed from this line, and is being replaced with CSS. Amtrak uses the Advanced Civil Speed Enforcement System (ACSES) for its Acela Express high-speed rail service on the NEC. ACSES was an overlay to the existing PRR-type CSS and uses the same SES transponder technology to enforce both permanent and temporary speed restrictions at curves and other geographic features. The on-board cab signal unit processes both
2627-419: The entire section, up to 12.7 km (7.9 mi). Thus, newer LZB installations, including all high-speed lines, break the cable loops into 300 m (984 ft) physical cables. Each cable is fed from a repeater, and all of the cables in a section will transmit the same information. The core of the LZB route centre, or central controller, consists of a 2-of-3 computer system with two computers connected to
2698-412: The existing lines, as additional distant signals would need to be added onto long blocks and the signals reworked on shorter ones. In addition, it wouldn't solve the other problem with high-speed operation, the difficulty of seeing signals as a train rushes past, especially in marginal conditions such as rain, snow, and fog. Cab signalling solves these problems. For existing lines it can be added on top of
2769-428: The existing signalling system with little, if any, modifications to the existing system. Bringing the signals inside the cab makes it easy for the driver to see them. On top of these, the LZB cab signalling system has other advantages: Given all of these advantages, in the 1960s, the German railways chose to go with LZB cab signalling instead of increasing the signal spacing or adding aspects. The first prototype system
2840-401: The figure shows the "monitoring speed", which is the speed which, if exceeded, the train will automatically apply the emergency brakes. When running at constant speed this is 8.75 km/h (5.44 mph) above the permitted speed for transited emergency braking (until speed is reduced) or 13.75 km/h (8.54 mph) above the permitted speed for continuous emergency braking. When approaching
2911-421: The first block was occupied it would be red as usual. Otherwise, if the first block was free and a LZB train approached the signal would be dark and the train would proceed on LZB indications alone. The system has spread to other countries. The Spanish equipped their first high-speed line, operating at 300 km/h (190 mph), with LZB. It opened in 1992 and connects Madrid , Cordoba , and Seville . In 1987
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2982-569: The inductive coil are assigned different meanings. Continuous inductive systems can be made by using the running rails as one long tuned inductive loop. Examples of intermittent inductive systems include the German Indusi system. Continuous inductive systems include the two-aspect General Railway Signal Company "Automatic Train Control" installed on the Chicago and North Western Railroad among others. A coded track circuit based system
3053-417: The information displayed to the driver has become out of date. Intermittent cab signalling systems have functional overlap with many other train protection systems such as trip stops, but the distinction is that a driver or automatic operating system makes continuous reference to the last received update. Continuous systems have the added benefit of fail safe behaviour in the event a train stops receiving
3124-572: The interlocking system from which they receive indications of switch positions, signal indications, and track circuit or axle counter occupancy. Finally, the route centre's computers communicates with controlled trains via the cable loops previously described. The vehicle equipment in the original LZB80 designed consisted of: The equipment in newer trains is similar, although the details may vary. For example, some vehicles use radar rather than accelerometers to aid in their odometry. The number of antennas may vary by vehicle. Finally, some newer vehicles use
3195-428: The nation's other large railways must equip at least one division with continuous cab signal technology as a test to compare technologies and operating practices. The affected railroads were less than enthusiastic, and many chose to equip one of their more isolated or less trafficked routes to minimize the number of locomotives to be equipped with the apparatus. Several railways chose the inductive loop system rejected by
3266-457: The number of trains present. Four fields in the call telegram are particularly relevant: The target speed and location are used to display the target speed and distance to the driver. The train's permitted speed is calculated using the trains braking curve, which can vary by train type, and the XG location, which is the distance from the start of the 100 m (328 ft) zone that is used to address
3337-421: The operator was permitted to travel at. Typically this was in conjunction with some sort of Automatic Train Control speed enforcement system where it becomes more important for operators to run their trains at specific speeds instead of using their judgement based on signal indications. One common innovation was to integrate the speedometer and cab signal display, superimposing or juxtaposing the allowed speed with
3408-406: The opposite. When a train enters a LZB controlled section of track, it will normally pass over a fixed loop that transmits a "change of section identification" (BKW) telegram. This telegram indicates to the train the section identification number as well as the starting zone, either 1 or 255. The train sends back an acknowledgement telegram. At that time the LZB indications are switched on, including
3479-483: The outputs and an extra for standby. Each computer has its own power supply and is in its own frame. All 3 computers receive and process inputs and interchange their outputs and important intermediate results. If one disagrees it is disabled and the standby computer takes its place. The computers are programmed with fixed information from the route such as speed limits, gradients, and the location of block boundaries, switches, and signals. They are linked by LAN or cables to
3550-433: 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. As the train approaches a speed restriction, such as one for a curve or turnout, LZB will sound
3621-562: The pulse code "signal speed" and the ACSES "civil speed", then enforces the lower of the two. ACSES also provides for a positive stop at absolute signals which could be released by a code provided by the dispatcher transmitted from the stopped locomotive via a data radio. Later this was amended to a simpler "stop release" button on the cab signal display. Automatic Train Protection Automatic train protection ( ATP )
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#17327732013153692-706: The right-of-way govern the movement of trains, as it provides the train operator with a continuous reminder of the last wayside signal or a continuous indication of the state of the track ahead. The first such systems were installed on an experimental basis in the 1910s in the United Kingdom, in the 1920s in the United States, and in the Netherlands in the 1940s. Modern high-speed rail systems such as those in Japan, France, and Germany were all designed from
3763-410: The same deceleration, a train travelling 200 km/h (120 mph) would require 1,543 m (5,062 ft) to stop, exceeding the signalling distance. Furthermore, as the energy dissipated at a given acceleration increases with speed, higher speeds may require lower decelerations to avoid overheating the brakes, further increasing the distance. One possibility to increase speed would be to increase
3834-424: The signalling information. Transponder based systems make use of fixed antenna loops or beacons (called balises ) that transmit datagrams or other information to a train as it passes overhead. While similar to intermittent inductive systems, transponder based cab signalling transmit more information and can also receive information from the train to aid traffic management. The low cost of loops and beacons allows for
3905-583: 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
3976-702: The speeds of some of their railway lines. One issue in doing so is signalling. German signals are placed too close to allow high-speed trains to stop between them, and signals may be difficult for train drivers to see at high speeds. Germany uses distant signals placed 1,000 m (3,300 ft) before the main signal. Trains with conventional brakes, decelerating at 0.76 m/s (2.5 ft/s), can stop from 140 km/h (87 mph) in that distance. Trains with strong brakes, usually including electromagnetic track brakes , decelerating at 1 m/s (3.3 ft/s) can stop from 160 km/h (99 mph) and are allowed to travel that speed. However, even with strong brakes and
4047-455: 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
4118-462: The start to use in-cab signalling due to the impracticality of sighting wayside signals at the new higher train speeds. Worldwide, legacy rail lines continue to see limited adoption of Cab Signaling outside of high density or suburban rail districts and in many cases is precluded by use of older intermittent Automatic Train Stop technology. In North America, the coded track circuit system developed by
4189-441: The state of the track ahead and can have the cab indication change at any time to reflect any updates. The majority of cab signalling systems, including those that use coded track circuits, are continuous. The German Indusi and Dutch ATB-NG fall into this category. These and other such systems provide constant reminders to drivers of track conditions ahead, but are only updated at discrete points. This can lead to situations where
4260-408: The switch instead of at a block boundary. See CIR ELKE below for details. The LZB control centre communicates with the train using conductor cable loops. Loops can be as short as 50 metres long, as used at the entrance and exit to LZB controlled track, or as long as 12.7 km (7.9 mi). Where the loops are longer than 100 m (328 ft) they are crossed every 100 m (328 ft). At
4331-547: The system might be in or if it is active at all. CDU's can also be integrated into the alertness system , providing count-downs to the alertness penalty or a means by which to cancel the alarm. Cab signalling in the United States was driven by a 1922 ruling by the Interstate Commerce Commission (ICC) that required 49 railways to install some form of automatic train control in one full passenger division by 1925. While several large railways, including
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#17327732013154402-593: The telegram type, and end with the CRC. Their data fields vary as follows: Before entering an LZB controlled section the driver must enable the train by entering the required information on the Driver Input Unit and enabling LZB. When enabled the train will light a "B" light. A controlled section of track is divided into up to 127 zones, each 100 m (328 ft) long. The zones are consecutively numbered, counting up from 1 in one direction and down from 255 in
4473-412: The track. A train identifies that it has entered a new zone by either detecting the cable transposition point in the cable or when it has travelled 100 metres (328 ft). A train can miss detecting up to 3 transposition points and still remain under LZB control. The procedure for entering LZB controlled track is repeated when a train transitions from one controlled section to another. The train receives
4544-402: 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
4615-422: The train. If the train is approaching a red signal or the beginning of an occupied block the location will match the location of the signal or block boundary. The on-board equipment will calculate the permitted speed at any point so that the train, decelerating at the deceleration indicated by its braking curve, will stop by the stopping point. A train will have a parabolic braking curve as follows: where: Where
4686-481: The wayside intermediate signals in the stretch of track between Elmhurst and West Chicago, requiring trains to proceed solely based on the 2-aspect cab signals. The Chicago, Milwaukee, St. Paul and Pacific Railroad had a 3-aspect system operating by 1935 between Portage, Wisconsin and Minneapolis, Minnesota . As the Pennsylvania Railroad system was the only one adopted on a large scale, it became
4757-543: The world, cab signalling standards were developed on a country by country basis with limited interoperability, however new technologies like the European Rail Traffic Management System ( ERTMS ) aim to improve interoperability. The train-control component of ERTMS, termed European Train Control System ( ETCS ), is a functional specification that incorporates some of the former national standards and allows them to be fully interoperable with
4828-629: Was developed by German Federal Railways in conjunction with Siemens and tested in 1963. It was installed in Class 103 locomotives and presented in 1965 with 200 km/h (120 mph) runs on trains to the International Exhibition in Munich. From this Siemens developed the LZB 100 system and introduced it on the Munich-Augsburg-Donauwörth and Hanover-Celle-Uelzen lines, all in Class 103 locomotives. The system
4899-406: 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
4970-400: Was overlaid on the existing signal system. All trains would obey the standard signals, but LZB-equipped trains could run faster than normal as long as the track was clear ahead for a sufficient distance. LZB 100 could display up to 5 km (3.1 mi) in advance. The original installations were all hard-wired logic. However, as the 1970s progressed Standard Elektrik Lorenz (SEL) developed
5041-517: Was the Speed Enforcement System (SES) employed by New Jersey Transit on their low-density Pascack Valley Line as a pilot program using a dedicated fleet of 13 GP40PH-2 locomotives. SES used a system of transponder beacons attached to wayside block signals to enforce signal speed. SES was disliked by engine crews due to its habit of causing immediate penalty brake applications without first sounding an overspeed alarm and giving
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