TGV
Introduction
This was the first operational high-speed line in Europe, between France's two largest
cities. It opened in 1981 with TGVs that ran regularly at 270km/h (168mph) and cut
the journey time between the two cities to 2 hours.
History of the line
In the 1970s SNCF, the French State Railways, was experiencing growth at a modest rate on its Paris-Lyon-Mediterranean line and reaching it's capacity fast
After some studies in either building a new line or upgrading the exciting tracks the new line won favour due to it being only about 40% higher in costs but alwaying a higher track speed
Route Information
The line starts outside of Paris, and runs directly to the edge of Lyon. To travel into the city centres the TGV runs on existing track but at conventional train speeds. About half way down there is a branch off into Dijon, where trains come off the high speed line, and run on conventional track to Dijon and then on into Switzerland.
However, once off the Paris-Lyon line, these trains are limited to conventional running speeds. Similarly many trains continue south of Lyon on existing track to the South Coast, although a new high speed line is being built now.
The Paris SUD EST Fleet 
In the early stages of TGV development gas turbine propulsion was considered. a high speed gas turbine set was built and was used as a test set for the development of the TGV. There were four basic rules were set for the new trains
1.Fixed formation train sets
2.Articulated configuration for passenger cars
3.body mounted traction motors
4.axle loading of 17 tons
Each PSE (Paris sud est.) consists of two power cars enclosing 8 coaches
They gain power from overhead wires. On the new TGV lines built the power is 25kV ac and on the other lines 1.5kV dc and as such when operating on the high speed lines only the rear pantograph is raised to collect power but on the 1.5 kv lines both pantographs are raised to collect the power
The first PSE set entered service in September 1981 .There are a total of 111 sets built each 200.2 metres long.
Each operating cab is equipped with air conditioning, train phone for communication with train crew ,radio link with a centralized train control center and TVM cab signalling
TGV Reseau 
This generation is visually indistinguishable from the TGV Atlantique, although it does have some differences. It was designed to run on the whole TGV network, and it has an important feature, the passenger coaches are pressure sealed. This is because when trains enter tunnels at speeds over 100mph or 160km/h, large pressure changes can occur which can be painful to passengers ears. This is the first train in the world to be sealed. Called Reseau because it means network. and this is designed as a full network TGV. It was introduced in 1993. This represented the 3rd generation of TGV, the first TGVs to have a design speed of 20Omph or 320kmfh. This is so the speed can be slightly increased from 186mph 300km/h if desired in the future.
The TGV Duplex 
The Duplex TGV belong to the third generation of the high-speed trains. Brought into service for priority on the Paris- Lyon line in 1996. Able to transport 45 % of passengers in more compared to one traditional car TGV, their mass varied little only thanks to the use of aluminum and revolutionary composite materials. Equipped with air-conditioning, the telephone. The cars are sealed For passing in tunnels. The cars are equipped with autopilot synchronous polyphase motors, of a rheostatic electric braking as well as TVM 430. In first class, the spacing of the seats is significant with three places of face and a possible slope by electric drive. The second class it also sees its improved comfort. The intermediate platforms were soundproofed and one finds some places there to calm down there. Intercar passage is done by the higher stage. The order fixed at 30 cars at the time of the first market signed with Alstom will be supplemented by 12 other elements which will come to reinforce the park in particular at the time of the opening from the TGV the Mediterranean in June 2001. With term, the speed reached by these cars will be of 320 km/h. Just like TGV PBA and PBKA Thalys , the Duplex cars are in compliable with cars TGV Network all equipped with the TVM 430, the motor coaches being technically similar if one excludes the central cabin and the manipulator traction with lever.
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The Record RUN
The Record run emerged out of a series of test runs. The aim was to achieve very high over 50Okm/h or 300 mph
Despite a very high world record of 320mph, 515km/h these speeds are not viable for commercial use, and may never be. There are problems encountered with pantographs contact and wear and tear to equipment is too high. Of course there are safety issues too which prevent civilians travelling at such high speed
The Average Speed
Between Lille Europe and Roissy CDG the TGV averages a speed of 254.5km/h or 158mph, second highest scheduled speed in the world. Still other TGV services often have very high average speeds often over 20Okm/h or 125mph. Note for comparison: The general average speed of the car is accepted as 45mph or 72km/h
Where TGVs run at full speed:
In order to run at speeds around 20Omph or 30Okm/h dedicated tracks have been built, called high speed lines, (Lignes a Grande Vitesse, LGVs). TGVs run all over France, however only about 30% of the TGV network rims on high speed lines. This is because a major high speed line is built, and then TGV services can have a fast run, then branch off onto normal railways to go into cities. On normal railways the TGV only reaches 138mph or 220km/h. Although this sounds fast in reality normal railway lines usually large amounts of speed restrictions because of curves and level crossings and through stations. As a result the speed of TGVs on non high speed line is very variable.
TGV Sud-Est
The TGV sud est.'s high speed line runs all the way from Paris to Lyon. About half way down there is a branch off the high speed line for services to Dijon, Strasbourg and Switzerland. Also Sud-est TGVs may go further south than Lyon, running on normal lines.
TGV Atlantique.
TGV Reseau
The TGV Reseau runs everywhere, along the high speed line between Paris and Brussels, and Paris and Calais (the line is where Eurostar and Thalys trains run at their full speed)
TGV Duplex
The TGV duplex is the double decker TGV. It only runs from Paris to Lyon, where the most traffic is. As a result it never travels on normal railway lines
Aerodynamics
Prior to the TGV's initial design, trains were not very aero dynamic. The front of the engines were basically square and caused much drag. When the model for the TGV was built, it looked futuristic with its sleek, curved nose.
Coupling
Another external feature is that the cars are semi permanently attached to each other. As the picture at the below shows, each car only has two axles, one at each end, compared with the traditional four axles on other trains. This is a marvel in design, because it drastically reduces the weight of each car. The axle design also helps to prevent the train from jackknifing in the case 
of an accident. Other factors included in this TGV design are: noise reduction, more space for a suspension, and improves aerodynamics (because the cars are sitting lower on the track).
Power Supply
The power supply of the TGV is overhead electric wires located along the tracks. The main transformer in the engine‑car receives 25kV from these wires an d converts it into 1 50OV, which is used to drive the train. The transformer is the heaviest part of the train,weighing about 8 tons.
Between the pantograph and the traction motors of a TGV there is a whole set of power electronics with the task of "processing" a fixed voltage at the (single-phase AC or DC) catenary to produce a variable force at the wheel treads. These power electronics fill most of the space inside a TGV power car.
We follow the power chain from pantograph to wheels, in the specific case of the TGV Atlantique 24000 series power car. The TGV 24000 does not contain any particularly exotic components, and in principle shares many of its features with most modern electric (and even diesel-electric) locomotives. The drawing below shows a cutaway view of the 24000, and is followed by a more detailed description. There are two power cars per trainset; each develops 4400 kW (5900 hp) and weighs just 68 tonnes (150,000 lb).
Drawing: B. Bayle (SNCF Direction du Matériel) in Revue Générale des Chemins de Fer, December 1986
Traction Components
GPU Pantograph: GPU means "Grand Plongeur Unique" (large, single plunger). [A pantograph is a device used to draw electrical power from a fixed overhead wire]. The GPU pantograph was specially designed, with a top linkage member (holding the wiper) that operates like a hydraulic damper with a short stroke to keep intimate contact with the overhead conductor and keep bouncing to a minimum. Contact wire pressure is about 70 N (17 lbs). The bottom linkage, wich guides alignment with the contact wire, is locked at a fixed height when operating under the fixed-height overhead on high speed trackage.
Main transformer: takes 25kV 50Hz single phase overhead power and converts this to 1500V 50Hz. For information on how transformers work, pick up any college physics textbook. The transformer is one of the heaviest components in the unit, weighing about 8 tonnes. It is located in the lower frame of the unit, and sits in a bath of oil, circulated by pumps and cooled with fans.
Thyristor controlled-rectifier bridge: as the name implies, rectifies the ouput of the main transformer to make 1500V DC. The thyristors allow a refinement beyond a simple diode bridge: they not only rectify the current, but can act as a switch and "chop" (turn on and off) the output power. This is why we speak of a "controlled rectifier". There are two thyristor-diode bridges, one for each pair of traction motors. From now on in the traction chain, in fact, there are two separate and independent paths to each of the two power trucks (bogies). This is to maximize reliability. (under 1500V DC overhead power, all that is used up to here is a thyristor chopper.)
(A note about the thyristor: these are made use of extensively in the TGV, just as in most modern electric locomotives. The development of the thyristor has made possible the use of frequency controlled AC traction motors and revolutionized traction circuit design. The thyristor is basically a switch, albeit a very large one, which resembles a common transistor in the way it works. A thyristor passes current only in one direction, called the "forward" direction, providing that a suitable voltage is applied to its control electrode, or "gate". As long as this gate voltage is not present, current cannot flow through the device.)
Common block: consists of the DC circuit breaker (two of them working in tandem, actually) and the main filter capacitor, which smooths the chopped 1500V waveform to a lower DC voltage, depending on the duty cycle.
Traction inverters convert their DC input into a computer-controlled three phase, variable frequency AC waveform, in order to conrol the traction motors. There is one inverter per traction motor. The inverters are thyristor-based. For each truck (bogie), the two inverter/motor pairs are connected in series. The power electronics physically associated with one truck (bogie) correspond to a "motor block" or "power pack". There are thus two such power packs installed in each power car. If one of them experiences a fault, it automatically isolates itself. The driver can then switch it back on, without leaving his station, by resetting the circuit breaker. But only once-- if the fault persists, the power pack will again trip out and, this time, stay down. This is not a problem in practice, since there is enough spare traction power available that the train can continue on its journey, on three packs out of four total. (Recall that TGVs have two power cars; one on each end of the train.)
Synchronous AC traction motor: the motor is excited at a frequency proportional to its rotational speed. There is no collector as on DC motors, which allows a reduction of wear and maintenance costs. (Note: the synchronous AC traction motor is different from asynchronous AC (induction) traction motor. Whereas the latter has a simple cage rotor with no power connections, the synchronous motor has rotor coils fed through slip rings.) In an unusual arrangement considered to be one of the TGV design's strong points, the traction motors are slung from the vehicle body, instead of being an integral part of the Y230 power truck (bogie). This substantially lightens the mass of the truck (each motor weighs 1460 kg), giving it a critical speed far higher than 300 km/h (186 mph) and exceptional tracking stability. The traction motors are still located where one would expect them: in between the truck (bogie) frames, level with the axles, but just suspended differently. Each motor can develop 1100 kW (when power comes from 25kV overhead) and can spin at a maximum rate of 4000 rpm.
Mechanical transmission: the output shaft of the motor is connected to the axle gearbox by a tripod transmission, using sliding cardan (universal-joint) shafts. This allows a full decoupling of the motor and wheel dynamics; a transverse displacement of 120 mm (5 inches) is admissible. The final drive is a gear train that rides on the axle itself and transfers power to the wheels. This final drive assembly is restrained from rotating with the axle by a reaction linkage.
Drawing of the Y230 power truck (bogie).
 Schematic of the TGV's tripod transmission. Sensors continuously compare motor speed to axle speed. A discrepancy between the measured speeds indicates a tripod driveshaft failure condition, which is indicated in the cab. If the tripod transmission develops a dangerous vibration, the shaking reaction linkage can strike a pneumatic valve that automatically dumps the main brake pipe and stops the train. Other ComponentsBesides the main traction chain, there is of course a whole suite of auxiliary equipment inside the TGV power car. Braking rheostat: large air-cooled resistors, located in the roof of the unit, used to dissipate braking power generated by the traction motors while braking. Also known as "dynamic brake"; in this application it is used exclusively at high speeds, and combined with wheel brakes as the speed drops below a predetermined level. Overall they can take up almost half of the braking energy in stopping a trainset from full speed. There are two sets of rheostats, one for each power pack. Their effective resistance can be modulated by the chopper to vary braking effort. Pneumatic block and wheel brakes: the main compressor is used to fill the air tanks used for the braking system. These tanks are located underneath the frame of the unit. There are two brake lines running the length of the trainset, as is common for the electropneumatic brake system used on most passenger trains. The first, the "principal line", is maintained at a pressure of 8 or 9 atmospheres at all times and is used to fill the auxiliary brake reservoirs on each vehicle in the trainset. The second, the "general line", modulates the wheel braking level between full application (3.5 atmospheres) and full release (5 atmospheres). Auxiliary power supply unit: a static converter that generates head-end electrical power for the rest of the train. HEP ("hotel power") is 380V 50Hz, while interior lighting is supplied with 72V DC. Output of the converter also runs some equipment in the power car: the transformer oil pumps and cooling fans, the brake rheostat cooling fans, the thyristor cooling fans, etc. Automatic coupler: the Scharfenberg-type coupler makes pneumatic and electrical connections without external intervention. It allows to couple two TGV trainsets nose to nose, either for normal multiple unit operation (even at high speeds) or for towing. When not in use, the coupler is concealed by two fiberglass clamshell doors that form the nose of the unit. These can open away to each side to reveal the coupler. Impact absorption block: is an impact shield to defend the cab cubicle. The deformation of this thick aluminum honeycomb block absorbs a part of the collision energy if a large object is struck. Frame: Primary structural members, made of high tensile strength steel. The main structure of the unit is a rigid space frame. In more recent designs, crashworthiness has been improved by including sacrificial frame members that collapse and absorb energy in the event of a large impact. Sinalling antennas: mounted under the front air dam, two antennas read TVM 300 (and more recently TVM 430) cab signal information from the rails, and relay them to the train's central computer (which in turn displays them to the engineer). There is a more detailed description of the signalling system available. On-board computer: manages all the subsystems. The computer can help to diagnose faults, and can even generate a maintenance report which is transmitted by radio to the shops prior to the train's arrival. Because the computer is so closely involved in every aspect of the operation of a TGV Atlantique unit, software glitches can cause annoying problems. Early teething problems in the computer systems actually made the TGV Atlantique initially less reliable than its older, lower-technology counterpart. TGV Trailers
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Braking System
The TGV trains use pneumatic brakes. They also have emergency disk brakes. The pneumatic brakes are more efficient because disk brakes would overheat and brake‑down from such high speed stoppages. Each axle is tied in to the main air‑braking system, which stores air at a pressure of approximately 8 atmospheres.
Computerized Signalling
Since the TGV is running at nearly 200 mph, the drivers cannot possibly see a sign on the side of the track. Thus, a computerized signalling system was implemented on all trainsets. The signals travel through the tracks and are picked up by the train using antennas that hang down from the nose. There are two components to this signalling system, one computer on the train, and one located on the ground, next to the tracks. These ground units control 10 mile stretches of track, and are hooked up to the main TGV control centre. The controls include track switches, notification of faults or other trains, to shutting off the air conditioning before entering a tunnel. The signaling of a high speed line requires a different approach from conventional railways. The speed of the trains is high enough that the engineer/driver cannot reliably read signals placed at trackside. The required vigilance cannot be expected of a human, especially for long periods and in adverse weather conditions. This is why the TGV system relies exclusively on cab signaling, a system by which signaling information is transmitted through the rails as electrical signals which are picked up by antennas placed under the train. This information is then processed by computers and displayed to the engineer/driver in the cab.
Cab signaling is not a new concept and is commonly used around the world for speeds above about 160 km/h (100 mph). The type of cab signal used on the TGV system is TVM, which stands for Transmission Voie-Machine or "track to train transmission". It should be noted that as futuristic as TGV trains may appear, the engineer/driver in the cab is still fully in charge of the driving task.
The TVM system was developped by the French group CSEE. It uses track circuits in both rails to transmit signaling information to the train's on-board computers, as well as fixed inductive loop beacons. It is one of the more advanced railway signaling systems in the world, although this should be kept in perspective as it relies on somewhat antequated components, for example... relays!
TVM is a fixed block system: the track is subdivided into fixed segments each of which has a particular state. Only one train may occupy any block at one time under normal operation. On the high speed lines TVM is permissive, in that a train may proceed at reduced speed (visibility allowing) after having been ordered to stop.
TVM 430
TVM 430 is the cab signaling system used on the latest TGV lines, and is an evolution of the earlier TVM 300 system, which operates on similar principles. As of 1996, it is used on the Nord-Europe line (LN3), part of the Rhône-Alpes line (LN4), and in the Channel Tunnel. It will be installed on the Sud-Est line.
TGV lines are divided into fixed blocks about 1500 m (1 mile) long. (The earlier TVM 300 system uses longer blocks.) Blocks are shorter than a train's braking distance, so a braking sequence takes place over several blocks, nominally four. This relatively frequent subdivision allows to run trains on shorter headways, which increases the capacity of a high speed line without placing additional requirements on the braking performance of the trains. Minimum headways (time between two succesive trains) are 5 minutes on the Sud-Est line (which uses TVM 300), 4 minutes on the Atlantique line (also TVM 300) and just 3 minutes on the Nord-Europe line, which is equipped with the newer TVM 430.
The following table illustrates the combined effects of speed and block length on braking distances and train headways.
| TVM 300 TGV-PSE |
TVM 300 TGV-A* |
TVM 430 TGV-R |
TVM 430 TGV-NG |
|
| Max Speed (km/h) | 270 | 300 | 300 | 360 |
| Nominal Block Length (m) | 2100 | 2000 | 1500 | 1500 |
| Normal Braking Profile (m) | 8400 4 blocks |
10000 5 blocks |
7500 5 blocks |
9000 6 blocks |
| Minimum Headways (mn) | 5 | 4 | 3 | 3 |
Note: some TGV Atlantique trainsets are fitted with TVM430
Blocks boundaries are indicated visually at trackside by square metal boards, blue with a horizontal yellow triangle (such as seen in the heading to this article). These signs are not critical to the task of driving a TGV, and they need not be seen by the engineer/driver.
Each block has certain properties which are relevant to the train occupying it. Invariant properties of a block are its length, its profile (uphill, downhill, flat), and a rated maximum safe speed, which is usually 300 km/h (186 mph). Properties that can change depending on the presence or absence of trains or other obstacles ahead are the target speed at the end of the current block, and the target speed at the end of the following block. A target speed is the speed at which the train should exit the current block and enter the next.
All of these pieces of information are relayed by the TVM 430 system to the train's computers and the cab display. The engineer/driver's responsibility is to follow the signal aspects indicated to him, but if he fails to do so he is closely watched by the train's computers, which can bring the train to a safe stop.
How Does It Work?
There are two components to the TVM 430 system: one ground-based, the other on board the train. Both run using Motorola 68020 class processors, such as those found in early models of the Apple Macintosh, and are programmed in Ada, a computer language often used in safety critical systems. The system makes extensive use of redundancy; the mean time between dangerous failures is estimated to be over 1 million years.
The ground-based segment of TVM 430 resides in trackside boxes, which control stretches of track about 15 km (10 mi) long. Each one is linked to the line's centralized traffic control center, and directly controls about ten blocks of track, each with its own track circuit. Signaling information is encoded in AC signals which are fed into the rails of each block. There are four different carrier frequencies available in TVM 430, and they are used alternatingly in pairs on both tracks of the TGV line. On one track, blocks use alternately 1700 Hz and 2300 Hz, while on the other track blocks use alternately 2000 Hz and 2600 Hz. Upon these carrier frequencies can be modulated 27 separate audio frequencies, any combination of which can be present at one time. (The earlier TVM 300 uses 18 separate frequencies, only one of which could be present at any time.) Each block has a receiver at the opposite end from the transmitter, and the loss of the track circuit signal (due to shorting by train wheels or due to a failure) is interpreted as an indication that the block is occupied. Signaling block boundaries are equipped with electrical separation joints that prevent adjacent blocks from interfering with each other while letting the traction return current (at 50 Hz) pass through. (The technical designation is the UM71 track circuit.)
The signals which are present in the rail are detected by antennas mounted underneath the front airdam of TGV trains, about 1 meter (3 feet) ahead of the front axle. These antennas work by inductively coupling to the AC signal shunted between the rails by the first axle. There are four redundant antennas per train, two at each end. Only the two at the "front" of the train (in the direction of travel) are used. The signal from the track circuit is filtered, conditioned, and decoded onboard the train by two redundant digital signal processors.
The decoded signal takes the form of a 27-bit digital word, with each bit corresponding to one of the 27 frequencies encoded on the carrier frequency in the track circuits. This word contains several fields, in the following order:
- Speed Codes
- The speed codes contain three pieces of information: the current maximum safe speed in the block, the target speed at the end of the block, and the target speed at the end of the next block. Each of these can take on five different values; in the case of a high speed line these are (in km/h) 300, 270, 230, 170 and 0, roughly corresponding to a typical deceleration profile.
- Gradient
- The gradient information is averaged over the length of the block. This allows the train's signaling computers to account for this in speed calculations.
- Block Length
- The block length can vary quite a bit, and is also important in speed calculations. For example, a flat stretch of high speed track, a block can be a full 1500 m (1 mile) long while in the terminal areas of the Channel tunnel blocks are ten times shorter.
- Network Code
- The network code is a number which determines the interpretation of the speed codes which should be taken by the train's computer. For example, on high speed lines where the maximum allowable speed is 300 km/h (186 mph), a different network code is used than in the Channel Tunnel, where the speed limit is 160 km/h (100 mph). Eurostar trains need this information since they operate both on high speed tracks and in the tunnel.
- Error Checking
- The error checking code allows to check the integrity of the entire 27-bit word. If the information has been misread, the error can not only be detected from the error checking code, but can in some cases be corrected. The code takes the form of a 6-bit cyclic redundancy check (CRC).
These 27 bits of information are used as an input to the train's signaling computer, the on-board part of the TVM 430 system. In older versions of TVM, the target speed was updated only at every block boundary, resulting in a "staircase" style speed profile which is not representative of the continuous speed changes effected by the engineer/driver. However, with the additional information of block length and profile, TVM 430 the train is able to generate a continuously varying target speed through calculations performed in the on-board signaling computer, thus giving a much more realistic speed profile of contiuous acceleration or deceleration for the engineer/driver to follow.
In addition to the continuous speed control afforded by TVM 430, single instructions can be passed to the train by inductive loops located between the rails, which couple to a corresponding sensor under the train. Using the same frequency encoding principle, 28 bits of information can be recovered from a beacon, at speeds up to 400 km/h (250 mph). The information passed along concerns a variety of actions, such as
- Indicating entry or exit from a high speed line
- Arming or disarming the TVM 430 system
- Closing air conditioning vents before entering a tunnel
- Raising or lowering pantographs
- Switching supply voltages
A passive recording system watches over the entire process, monitoring a variety of parameters, not unlike the "black box" in aircraft. In TVM 430 equipped trainsets, the older graphical recording equipment has been replaced by the ATESS digital recording system. Every action of the engineer/driver (throttle, brakes, pantographs, etc) as well as signaling aspects (for TVM 430, KVB, and conventional signals) are recorded on tape for analysis using a desktop computer.
What Does The Engineer/Driver See?
The image above shows the control desk of a TGV Duplex. In the center of the desk, just below the windshield, there is a double row of square indicators. This is where target speeds for the current and subsequent blocks are displayed to the engineer/driver, in the form of numbers (in km/h) on a color-coded background. Full line speed is indicated in black numerals on a green background, while slower aspects are indicated in white numerals on a black background and a full stop is indicated as "000" on a red background. Below this display is the speedometer, where the continuously varying target speed is indicated as well as the current speed. (Speed is measured by a redundant tachometer to a precision of 2%.) The allowable variation between target speed and actual speed is dependent on speed, and is smaller at higher speeds. For an indication, under a 300 km/h aspect, the computer will take action only if the train exceeds 315 km/h.
A very complete description of TVM signal aspects and braking sequences was prepared by Thierry Davroux, and is well worth the visit. It is only available in French. The different speed codes, as displayed to the engineer/driver, are explained in detail.
All the in-cab signaling displays must be very reliable, since they are critical to safety. They have relay-based position sensors which feed back to the signaling computer the current aspect being displayed to the engineer/driver. If there is a failure in the display unit, appropriate action is taken to stop the train.
In order to reduce stress on the engineer/driver, speeds are displayed over several blocks ahead of the train. When a block is followed by a more restrictive (slower) block, the display for that block flashes so the engineer/driver can better anticipate the speed change. Restrictive indications can only be updated at block boundaries, except in emergencies. They are accompanied by an audible in-cab horn signal. Restrictions can however be lifted at any time within a block.
TVM 430 has extensive redundancy built into it, and one might wonder why it isn't used to control the train directly. However, in view of the lack of adaptability of the system to unexpected situations, it is considered desirable to retain a human in the loop. Driving a TGV is therefore done entirely manually, but the signaling system keeps a very close watch to ensure maximum safety.
Additional Signaling Systems
The TVM system is used only on high speed lines in France. Outside of the high speed lines, other signaling systems are used, and every TGV train is equipped with them. KVB (Contrôle Vitesse par Balise, or "beacon speed control") is used throughout the French standard network and is therefore present on all TGVs. In addition to TVM, then, the following systems are used in various combinations:
- KVB the French signaling system (electro-mechanical with radio beacons)
- ATB the Dutch signaling system (induction based)
- ATB-NG a newer version of ATB (also induction based)
- MEMOR the Belgian signaling system (electro-mechanical)
- TBL a newer version of MEMOR (electro-mechanical with radio beacons)
- InduSi the German signaling system (induction based)
- LZB the German system for high speed lines (also induction based)
- AWS the British signaling system (induction based)
This can make for some rather complicated signaling displays, especially on the new 4-system Thalys TGVs which are designed for international service.
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