Railway Signals in Goyanes

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An L-Class signal showing a clear aspect with a caution distant signal. This indicates that the current block is clear, but the next main signal should display a stop aspect.

Railway signals in Goyanes evolved from electro-mechanical semaphores that changed position to indicate track block status. Before then though, railways employed “track officers” to manage sections of track using hand gestures, line-of-sight techniques, and physical tokens that had to be passed from train to officer and vice versa. This was wildly inefficient, and as the railways grew, technologies were developed to reduce collisions and improve railway safety. Starting with the Grand Trunk Railway and spreading quickly around the nation, electric track circuits that controlled semaphore signals began to take hold. The process started in the 1870s, but by the 1890s, Goyanes’ railway network was fully electro-mechanically signaled.

In 1902, the Stortoghass Tunnel Crash in Gojannesstad occurred, where a through train engineer running a service from the Hysende-Osanhalt-Kongsland Railway onto the grand trunk in Gojannesstad became confused by the Grand Trunk's signal system, and crashed the train, resulting in 30 deaths and more than 50 injuries. This caused the Ministry of Transportation (then known as the Ministry of Railways) to mandate a new, unified, national signal system. The new signal system became known as M-Class signals (M-klassesignalen). M-Class signals used semaphores and relays, and a unified set of meanings. This helped promote inter-operation, and created a stanrdized and safer working environment for the railways.

By the early 1930s, the Ministry of Railways had consolidated all of Goyanes' railways into four companies, the Grand Trunk, the Hysende-Osanhalt-Kongsland, the Nordstrom Seabord, and the Hirendag Road. As part of this consolidation effort, a new signalling system based on color-light aspects was introduced. This became known as the L-Class signals (L-klassesignalen). The L-Class also introduced a new safety system known as ATS-M. ATS-M uses electromagnetic induction to warn the driver that they have passed a cautionary aspect, and stop the train if a signal has been passed at danger. The ATS-M system, in addition to L-Class signals are still used on all classic lines today.

The devolopment of the HHT system in the 1960s and 1970s forced Gojan Jårnbaner, Goyanes' state railway operator, to develop a cab signalling system. The high speeds of the HHT system prevented operators from being able to see and comprehend any trackside signals, so a system that transmits speed and track information directly to the driver was created, known as AVK. AVK is currently on its second iteration. In addition, a new system known as HBK that uses train-mounted microprocessors and track-mounted beacons to enforce speed limits set by both track conditions and signal state. HBK is installed on all classic lines in Goyanes.

In the 1990s, in an effort to modernize and increase frequency on Goyanes' classic lines, AVK was installed on certain classic lines to increase frequency. In additon, a new signalling system that was able to understand and adapt to the abilities of more modern rail equipment (high speed switching points and quicker braking curves on trains). This system became known as the A-Class signals (A-Klassesignalen).

Currently in Goyanes, all signals are either L- or A-Class, all classic lines and trains are equipped with HBK, and high-speed trains and lines are equipped with AVK. The introduction of A-Class signals did not completely phase out L-Class signals, and retrofitting is done on a per-line basis, with higher-throughput lines getting switched over first, and lesser used primary and secondary lines later. About half of the classic network still uses L-Class signals.

L-Class Signals

Signals in Goyanes are based on the distant-main block system. Distant signals (Vørsignalen) alert the driver to the aspect of the next main signal (Hovedsignalen), so that the driver may act accordingly in time for the main signal. Both L- and A- type signals may be used for main line traffic up to 190 km/h. Above 190 km/h national regulations require the use of cab signalling.

Main signals (Hovedsignalen) are called so because they can display a stop aspect. If the stop aspect shows, it may not be passed without authorization, and is therefore considered a very important point in the track layout. Therefore, they earned the name "main signal." A main signal can be recognized by its rectangular shape. They may contain either one or two vertical rows of lights, however they will always be taller than they are wide.

Main signals are used at several places along the lines. They are used at the entrances to stations, at which point they are called "home signals" (Hussignalen), at the exits of stations, where they are called "exit signals" (Utgangsignalen), so break the track signals into blocks, and to guard interlockings. For the latter two they are simply known as main signals. After the introduction of the A-Class signals in 1990, certain changes were made to the L-Class for safety purposes. First, home signals will display a board over the signalhead with the letters "HUS" on them, and some signals protecting interlockings were retrofitted with a board depicting a white diamond on a black background.

An example of how distant signals work. Both distant signals show that the main signals are displaying stop. If you look through the tunnel, the main signals are displaying a stop aspect.

Distant signals (Vørsignalen) announce to the driver what will be shown to the driver at the next main signal, thus their name. A distant signal cannot stop a train, but they can slow one down in time for a stop signal or a diverging set of switch points. Distant signals are always square-shaped. For there to be a distant signal, there must either be a main signal or an end of track. However, you do not need a distant signal attached to a main signal. For any tracks (always secondary lines) where the speed limit is less than 40 km/h or of the railway uses cogs in the center of the track (alpine routes), the use of distant signals is optional, however once the track speed is above 40 km/h, use of distant signals is mandatory.

Distant signals can be mounted allong with a main signal on the same mast. The distant signal must be mounted below the main signal on the mast. Distant signals are only mounted on the main signal if the next block is 1200 meters or less. If it is more than 1200 meters, there will be a separate distant signal before the main signal it protects.

The following graphics show main signals with the distant signals that announce them mounted below. In most circumstances the next signal aspect displayed by the distant signal would be different. In addition, the main signals shown have the capability of displaying all aspects. In most circumstances, main signals can only display certain aspects that relate to the condition of the lines they protect, and as such could have as few as three or four lamps, instead of the seven pictured here. Regardless, the light and color combinations carry the meaning, not the total amount of bulbs on the signalhead.

Aspect	Meaning
	Stop All trains must stop before the signal, or they risk tripping the ATS-M system and forcing an emergency stop. The signal may only be passed after permission from the dispatcher is given. The distant signal is placed at a safe braking distance from the main signal it protects. The distant signal indicates that the should expect the next main signal to display a stop aspect. Sometimes when a Stop signal is displayed and a distant signal is mounted under the main signal, the distant signal's lights may be shut off. This does not affect the meaning of the main signal.
	Clear The train may pass at the maximum permitted speed, either by trackside signs or the timetable, whichever is slower. The distant signal indicates that the should expect the next main signal to display a clear aspect. On switchpoints that can be passed at track speed, even if the signal displays clear, this aspect may apply for a diverging route.
	Caution 40 The track is clear, but the train may travel no more than 40 km/h after the first axle of the train passes the main signal. This signal may be used to enforce a braking curve on heavier trains or to govern a switchpoint that has a 40 km/h limit. If the timetable or posted speed is slower, it must be followed instead. The distant signal indicates that the main signal is showing a caution 40 aspect, and the driver should begin braking so that the train passes the main signal at 40 km/h or slower. This distant signal may also indicate that the next signal is displaying the "Short Block" or "Proceed Occupied Block" aspects, and that the driver should slow down to 40 km/h or less before passing the next signal.
	Caution 60 The track is clear, but the train may travel no more than 60 km/h after the first axle of the train passes the main signal. This signal may be used to enforce a braking curve on heavier trains or to govern a switchpoint that has a 60 km/h limit. If the timetable or posted speed is slower, it must be followed instead. The distant signal indicates that the main signal is showing a caution 60 aspect, and the driver should begin braking so that the train passes the main signal at 60 km/h or slower.
	Caution 90 The track is clear, but the train may travel no more than 90 km/h after the first axle of the train passes the main signal. This signal may be used to enforce a braking curve on heavier trains or to govern a switchpoint that has a 90 km/h limit. If the timetable or posted speed is slower, it must be followed instead. The distant signal indicates that the main signal is showing a caution 90 aspect, and the driver should begin braking so that the train passes the main signal at 90 km/h or slower.
	Short Block The track is clear, and the next signal is displaying stop, but is unusually close. Any distant signal at a main signal displaying "Short Block" is shut off. Due to the abnormally short block, there is no adequate braking curve and the train must proceed at no less than 40 km/h. This signal usually protects tub platforms at stations, as there is no safe braking distance.
	Restricted The track status is unknown, and the signal is displaying this aspect potentially due to a defect or other condition. The train may proceed at a maximum of 30 km/h or whatever lower speed the driver wishes. The train must be able to stop for any obstructions. The indicator below the distant signal allows the stop aspect to become permissive, as it is diagonal. If the indicator was showing a horizontal aspect, this would be considered a standard stop aspect.
	Proceed Occupied Block The block is occupied by another train. The train must proceed at 40 km/h or less, and follow the authority of trackside personnel to stop short of, or couple to another train. Sometimes when a train needs to be coupled, and this aspect is not available, dispatch may order a train to proceed through a stop signal.
	K-System Stop On certain distant signals that are freestanding, a small white sign with a black dot may be placed above the signalhead. This indicates that if the signal is shut off, the aspect means stop.On lighted signals displaying this aspect, the board on top means that the distant signal could be treated as a main signal. K-System is only used where there are lower speed limits and very short blocks. For turnouts at switchpoints, the newer speed limit becomes enforced at the 2nd instance of the caution speed signal.

A-Class Signals

By the end of the 20th century, it became apparent that Goyanes' L-Class signalling system was not adequate for modern rail travel. The braking curves that were integrated into the system were designed for steam and early electric locomotives that took much longer to brake and accelerate. In addition, railway technology had advanced, and by now, switchpoints had been constructed with the ability for high-speed transit, making the previous aspects useless in some areas.

Regarding braking curves, by 1980 there were 190 km/h trains in operation on classic lines. With the next possible speed downgrade on the L-Class system being to 90 km/h, it represented a waste of time to slow trains down to 90 km/h to transit a switch that coupld have been passed at 120 km/h. Upgrading the L-Class system with more aspects would have made the system more complicated and difficult to understand, so Gojan Jårnbaner decided to design a new signalling system for the future of the network.

The new requirements of the system were more fine-tuned braking curves, and an easier to understand color-light system for the drivers. The previous L-Class had been based on mechanical semaphores, and training was easy when drivers already understood the semaphores. However, now that they were gone, the system became increasingly more complex to explain. As a result a much simpler system had to be developed.

The new system that was developed was easily integrable into the L-Class network, and used principles of the K-System, where distant and main signals were combined on certain signals, which was already familiar to drivers. The system was designed by engineers, and used high-school students as a control group in addition to drivers to ensure that the system was easy enough for novice drivers to understand, while still maintaining all the needed design features.

As all A-Class signals can display both a distant and a main signal aspect, several changes had to be made. The first, signals that had no ability to display stop using a light have square borders. The second, signals protecting station entrances (home signals) display a board that says "HUS" over the signalhead to indicate it is a home signal. Third, signals protecting interlockings have a board over the signalhead that shows a white diamond over a black background. The latter two have been incorporated into the L-Class signals.

Similarly to the L-Class signals, if a block section is more than 1200 meters, there will be a separate distant signal that uses a square signalhead before the main signal. Otherwise, standard round signalheads can represent upcoming changes in the signal state.

Distant Signal	Main Signal	Meaning
		Clear The train may pass at the maximum permitted speed, either by trackside signs or the timetable, whichever is slower. The nature of the A-Class signal means that the next signal will also be displaying a clear aspect.
		Speed Limit The train must pass the signal at or below the speed indicated by the number below x 10. (In this case 7, therefore 70 km/h.) The distant signal indicates that the driver should begin braking, expecting the next signal to show a speed restriction.
		Short Block 40 The train must pass the signal at or below 40 km/h. In addition, the next signal is showing stop and is abnormally close to this signal. The distant signal indicates that the driver should begin braking, expecting the next signal to show a speed restriction of 40 km/h or a slow stopping aspect such as this one or a Caution 40.
		Caution 40 The train must pass the signal at or below 40 km/h. In addition, the next signal is showing stop. The driver must be prepared to stop before the next signal. The distant signal indicates that the driver should begin braking, expecting the next signal to show a speed restriction of 40 km/h or a slow stopping aspect such as this one or a Short Block 40.
no signal		Short Block Caution The driver must reduce speed to be able to stop at the signal after next, which is showing the stop aspect and is closer than the normal braking distance to the next signal.
		Stop All trains must stop before the signal, or they risk tripping the ATS-M system and forcing an emergency stop. The signal may only be passed after permission from the dispatcher is given. The distant signal is known as a Caution aspect, and is placed at a safe braking distance from the main signal it protects. The distant signal indicates that the should expect the next main signal to display a stop aspect. There may be several slow-down speed restrictions before a caution aspect to bring the speed down for the braking curve. Any prior speed restrictions apply.
		Restricting The track status is unknown, and the signal is displaying this aspect potentially due to a defect or other condition. The train may proceed at a maximum of 30 km/h or whatever lower speed the driver wishes. The train must be able to stop for any obstructions. This signal is used as well to couple trains at station, therefore directions of any trackside personnel must be obeyed.

Shunting/Dwarf Signals

Shunting signals, also known as “dwarf signals” (kleinesignalen), are used for shunting purposes in yards. They are smaller in size, and use only white aspect colors. They may be placed on top of a half-height post, or placed at the same height as the trackbed.

Signal		Meaning
	Danger	The signal must not be passed without radio permission from dispatch.
	Movement Allowed	Movement is allowed. All points and derailers have been set. The track ahead is clear. Speed limit 30 km/h. This aspect is commonly used to allow permittivity of a signal at danger.
	Movement Allowed with Caution	Movement is allowed Points and derailers are in the right position. The track is not clear however. Speed limit 20 km/h. This aspect is commonly used to allow permittivity of a signal at danger, specifically to couple/shunt trains already in a platform or a siding track. The train must come to a complete stop before continuing.
	Movement Allowed Check State	Movement is allowed All points and derailers may not have been set. Driver must ensure all points are set as well as clearance ahead. This aspect is used to grant entrance into yards with manual track points and no electronic control.

Railroad Crossing Status (RCS) Signals

A main RCS signal displaying "Crossing Not Secured/Danger"

RCS signals (Vagersignalen or VS) are used to indicate to the driver the status of a railroad crossing ahead on the line. Various factors affect the aspect displayed. The most simple kinds simply confer if the gates are closed and locked, but the most advanced types rely on sensors that can detect if vehicles are stalled on the crossing, in addition to detecting whether or not they have been locked. There are two types of RCS signals, just like color-lights, they are Main Signals and Distant Signals. Main RCS signals are identified by a “V” sign under the bulbs. Distant RCS signals are identified by their shape and unique bulb layout.

A related signal called a Bridge Status Signal (Bryggesignalen or BS) uses the same signalheads and aspects, except the main BSS signals have a "B" signpost under the signal head, similar to how main RCS signals have a "V" signal on them.

Main RCS Signals (Hovedvagersignalen/HVS)

Signal		Meaning
	Crossing Not Secured Danger	The crossing is not secured, the train must attempt to stop before the crossing. Emergency brake application is acceptable.
	Crossing Secured Proceed	The crossing is secured, proceed normally.

Distant RCS Signals (Vørvagersignalen/VVS)

Signal		Meaning
	Expect Crossing Not Secured (Crossing not clear)	The Main RCS signal is at danger, the driver must slow the train down immediately and attempt to stop before the crossing. Emergency brake application is acceptable.
	Expect Crossing Secured (Crossing clear)	The Main RCS signal is showing secured, proceed normally.

AVK System

The orange sign indicating a non-permissive track block. On the opposite track an E2 series HHT train is entering the station area at Orkanger, Nyhett.

The AVK system was invented in 1959 and inplemented in 1964 for use on HHT high-speed services, as operators would not be able to read and interpret lineside signals at high speed. AVK-1 was the first iteration of the system invented, with the second and current iteration being known as AVK-2. Signaling information is instead transmitted to the train and displayed as part of the train controls. The driver is shown the safe operating speed, displayed in kilometers per hour. The late-1990s-developed AVK-2 system transmits more information than traditional signalling would allow, including gradient profiles and information about the state of signaling blocks much further ahead. This high degree of automation does not remove the train from driver control, although there are safety mechanisms that can safely bring the train to a stop in the event of driver error or incapacitation.

History

The AVK system was developed by Gojan Jårnbaner engineers in conjunction with the Eindrisson company, which currently markets the system worldwide. It was first tested on several conventional lines to ensure the system would work when transfered over to the high-speed lines. The AVK-1 system went online in the first section of the HHT system to open, the Gojannnesstad-Naderfjord high-speed railway.

AVK-1 was a relay-based system that used rigid blocks, and communicated with the train using pulse codes sent to the train based on the signal state. The pulse codes are sent theough the front axle of the train as it bridges the circuit across the two rails, and the pulse code is interpreted by a sensor on the train, which otputs a maximum permitted speed based on the track limits and the block status ahead. However, as the train slowed down, the rigid block system caused an uncomfortable braking experience, which required lowering speed, then easing off the brakes, then braking harder again. This, among other things, prompted the development of AVK-2.

By 1999, in addition to the creation of the A-Class signal system, the engineers decided to improve the AVK system with new microprocessors both onboard and trackside, and a new, more computerized trackside system. The new system was called AVK-2. AVK-2 was marketed by Eindrisson engineers as part of a multi-tiered approach. AVK-2 would be standard operation (cab signalling and automatic train protection from overspeed and stop signals), AVK-2.1 (optional automatic train control), and AVK-2.2 (fully automatic operation).

In 2010, the AVK system was applied on certain classic lines to test throughput capacity. It proved successful and now, certain very-high capacity lines have had the AVK-2 system installed to increase frequency of trains.

Implementation

In AVK-2, the track is dotted with transponders mounted in the center of the track every usually 200m to 1 km (in some schenarios they can be as close as 10 meters, such as at where a side track joins a main line). The sections of track block are guarded by transponders at both ends, but there are usually transponders inside the track block as well. The track block uses a standard track circuit to detect the position of a train. Lineside equipment stations transmit the last updated distance to the next train to the train via the transponder, as well as the maximum permitted line speed.

An old-style transponder coil located along the platform at Ingolfur Station. These models are compatible with the new ones, but are being replaced.

There is a main equipment box that controls about 10 blocks, which in turn is controlled by the central control room for that line. The central control room is able to integrate the AVK-2 system with the scheduling system to maintain precise headways, and ensure safety of operations.

Onboard the train, as it passes over a transponder, the distance to the train ahead, maximum line speed, and track gradients are recieved, and this information is sent to the onboard computer, which determines a braking curve using the given information and known information such as train acceleration and braking performance. The computer then displays an authorized speed on the dashboard. The authorized speed is constantly being recalculated, as the train estimates its position to the train ahead, and along the line (for gradient purposes) using the onboard odometer. The distance is confirmed/reset every kilometer when the train passes over a transponder, which subsequently updates the train on its current position.

When the train reaches the point where the computer determines it should begin braking, or if it passes a transponder and an updated speed is given, an alarm sounds in the cab which the operator must confirm. Then the braking curve begins. The operator should brake normally, but keep an eye on the speedomoeter, as the speed limit decreases in real time. If the speed of the train exceeds the maximum authorized speed, either while cruising or braking, the train will apply brakes to bring it below the authorized speed. The continuously dynamic braking curve drastically improves passenger comfort, and allows for closer headways. Once the authorized speed stops decreasing, a bell sounds in the cab.

A lineside equipment station on the Nyhett Valley High Speed Line. An new-style AVK transponder is visible in the lower right in the track.

The signalling system is permissive; the driver of a train is permitted to proceed into an occupied block section without first obtaining authorisation. An occupied block section is indicated on the speedometer by a speed limit of 30 km/h. When the speed limit is 30 km/h, the train cannot exceed 32 km/h, and must stop before any obstructions, track defects, or trains ahead. Non-permissive blocks, such as at entrances and exits to stations, and at interlockings, are marked with an orange, diamond-shaped, board with a black cross. There will always be a transponder protecting the block, as well as a dwarf signal. If a driver encounters a non-permissive board, they must do two things. First, they must check the speed indication. If it is not 30 kmh, they may proceed as normal. If 30 km/h is given, they must look at the dwarf signal at the non permissive sign, if it displays stop, they must stop before the board, and if it displays proceed or proceed with caution, they can pass the board. Entering a non-permissive block at danger will trigger an emergency brake application. Non-permissive blocks can also be guarded by a single color-light, as is the case on newer tracks. If the section is protected, a red light will illuminate. GJ has been swapping the dwarf signals for color lights since 2010 as they offer improved visibility.

A dwarf signal protecting a non-permissive track section. The light above the dwarf signal is the new color-light which has replaced the dwarf signal.

The additional information passed along by the transponders can concern a variety of events or actions, such as signal system changes at the entry or exit of a high-speed line, arming or disarming the AVK-2 system, closing air vents before entering a tunnel at speed, raising and lowering the pantographs, or changing the supply voltage at system barriers. When trains enter or leave the high-speed line from classic lines, they pass over a ground circuit which automatically switches the driver's dashboard indicators to the appropriate signalling system. For example, a train leaving the high-speed line onto a classic line would have its AVK signalling system deactivated and its traditional ATS (automatic train stop) and HBK (automatic speed control) systems activated by the train's onboard computer at the boundary point.

Oversight

A "black box" similar to an aircraft flight data recorder, passively watches over the entire process, monitoring a variety of parameters and recording the events onboard the train. In AVK-2-equipped trainsets, older paper-strip recording equipment has been replaced by a digital recording system. Every action taken by the driver (throttle, brakes, pantographs, etc) as well as signalling aspects (for AVK-2, and conventional signals (via the ATS and HBK signals) are recorded on magnetic tape for later analysis using a desktop computer.

Another system, known as FK, oversees the driver's alertness. The FK system is located in the brake handle. The handle itself is a button, and when the handle is pressed down, the train can operate. The FK system asks the driver to release and depress the brake handle every 60 seconds if there has been no input to the train's controls. The timer resets every time there is an action. If the handle is released, there is a grace period of about 15 seconds before an alarm sounds. If the alarm sounds for 10 seconds, the emergency brakes are applied.

A small amount of overspeed allowance is allowed before the AVK system will activate the emergency brakes. For 30 km/h the tolerance is 2 km/h. Below 80 km/h, the tolerance is 5 km/h. Between 80 km/h and 160 km/h it is 10 km/h. At speeds in excess of 160 km/h, it is 15 km/h. If the speed is in the tolerance speed, an overspeed warning buzzer sounds, and is not deactivated until the speed goes below the limit speed again. If the speed exceeds the safety tolerance the buzzer switches to an alarm and the brakes apply to bring the speed within the tolerance. If the driver does not aknowledge the alarm and safety braking after 5 seconds of braking, the emergency brakes will activate and the train will be stopped. The alarm does not switch off until the train comes to a complete stop.

Cab Display

In the centre of the driver's desk in an HHT cab, or on any other AVK-equipped train, just below the windscreen, there is the speedometer. The permitted speed is showed in a bar over the actual speed, as well as on a numerical readout next to the speedometer. As the braking curve is enforced, the speed limit bar decreases in real time, allowing the driver to adjust his braking rate accordingly. All the in-cab signalling displays must be very reliable, since they are critical to safety. The coded software is safety-critical, and enforces that the current aspect being displayed to the driver is correct. If there is a failure in the display unit, appropriate action is taken to stop the train.

The speedometer aboard an E5 series HHT train. The blue bar represents the AVK-permitted speed, the green bar represents the actual speed. A numerical display provides a backup readout, partially visible to the right of the screen.

AVK-2 has extensive redundancy built into it, and one might wonder why it is not used to control the train directly. However, keeping in mind the lack of adaptability of the system to unexpected situations, it is considered desirable to retain a human in the loop. Driving an HHT is therefore done entirely manually, but the signalling system keeps a very close watch to ensure maximum safety.

Automatic Train Stop (ATS)

Automatic Train Stop (Automatisk Togstanna/ATS) is a system that governs color-light signals that are displaying a stop aspect, or any sort of cautionary aspect. The current ATS system (ATS-M) was invented at the same time as the L-Class signal system. Previous ATS systems relied on mechanical infrastructure, such as tripcocks opening brake valves when a signal was passed at danger. Such systems still exist on select railways, such as the Gojannesstad U-Baner, among others. However, on the GJ network, the ATS-M system is operational.

A legacy ATS system that uses a tripcock on the Naderfjord U-baner. The tripcock is armed on the left and disarmed on the right.

The ATS-M trackside reciever in the center of the rails and the trackside transmitter on the outside of the rails.

ATS-M functions using both trainside and trackside infrastructure. Trainside, there is an electromagnetic impulse transmitter located under the leading car or locomotive, along the centerline, and an electromagnetic impulse reciever that hangs on the right side (in the direction of travel), offset several centimeters from the edge of the rail, and connected to an alarm and pushbutton in the cab, as well as the power and brake system. On some locomotives/multiple unit cars there may be two recievers (one on each side). If so, before departure a switch is set in the cab to indicate which reciever should be used (standard practice is to use the right-side reciever). Trackside, there is a reciever lined in the center of the track (underneath where the train's transmitter would pass) which is connected to a transmitter on the outside of the rail (underneath where the train's reciever passes).

The ATS-M trainside transmitter under the center of the locomotive and the trainside reciever on the side of the locomotive.

When the train's electrical system is on (required for it to move), the transmitter is constantly sending positive electromagnetic pulses. This interacts with the ATS-M array at a signal as it passes over it. When a signal is displaying a clear aspect, the ATS-M array disconnects the track's reciever from the track's transmitter. Therefore, as the train passes the signal, there is no interaction, so the train proceeds as normal.

The ATS-M console in the cabin of a train. The light/confirmation button is in the center, and is turned to aknowledge. The ovveride switch is labeled "M" on the right side for "manual."

When the signal displays caution, the trackside arrays connect, and a polarizing circuit connects, so when the train passes over the array, the reciever picks up the positive impulse, and transmits a positive impulse back via the side transmitter. The train reads the positive impulse through its side receiver, which triggers a buzzer in the cab and activates a caution light which stays on until the confirmation button is pressed. If the confirmation button is not pressed after 5 seconds, the emergency brakes activate and the power is cut off.

When the signal is displaying a stop aspect, the the trackside arrays connect, however the polarizing circuit does not connect, so when the train passes over the array, the reciever picks up the positive impulse from the train, and transmits a negative impulse. The train reads the negative impulse on its reciever, which triggers automatically the emergency brakes and cuts all power systems.

The ATS-M system may be overridden (in case of a shunting movement or to pass a restricting signal) by holding down the override button as the train passes over the magnet. Mechanical ATS systems such as on the U-Baner cannot be overridden except by dispatch due to the nature of the system.

ATS-M is currently being supplanted by a system known as ATS-H. ATS-H is completely digital, using beacons mounted in the center of the track similar to the HBK system, and in fact it combines the speed checking aspects of HBK with the signal checking of ATS-M. It functions in the same way as ATS-M in how it communicates with the driver. More information is in the section below.

Speed Limit Control (HBK)

Two HBK beacons (yellow plates in the center of the track) located before the ATS-M array at a signal post at the exit to a station in a village in Goyanes.

The Speed Limit Control System (Hastiketbegrensekontroll/HBK) is used to enforce maximum track speeds and speed restrictions into turnouts. It is a relatively modern system, having been created along with the A-Class signalling system in the 1990s. The HBK system supplements the ATS-M system used on classic networks by ensuring that the speed limits are not broken and that trains brake in time for switch points. The system, similarly to ATS-M or AVK, uses both trackside and onboard equipment. The trackside equipment consists of equipment boxes with microcontrollers that are connected to the signal system, and to a phone line (GSM-R since 2010 or a wired phone line before 2010) for communication from dispatch of temporary restrictions to be enforced. The microcontroller determines the signal state, and is programmed with the track speed limit, and any of the day's temporary limits. The microcontroller then transmits information to a beacon mounted in the center of the track.

A reciever on the train decodes the signal from the beacon, and sends it to the HBK computer onboard. The HBK computer compares the speed just recieved by the beacon to the onboard displayed speed. If the train is at or below the speed limit, nothing is done. If the train is within 10 km/h of the speed limit (above 60 km/h limit) or within 5 km/h (below 60 km/h limit), an overspeed alarm sounds, alerting the driver to lower the speed. If the speed of the train is above the tolerance, the emergency brakes are automatically applied and the power systems are cut.

The HBK system stores the latest recieved track speed, and keeps it in the memory for constant comparison against the speedometer until it is overriden by a new track speed picked up by the reciever from another beacon. In track areas unprotected by HBK (at the transfer point between a GJ and non-GJ line, or at the interface between the classic lines and the high-speed lines) there is a final beacon that deactivates the system by clearing out the memory bank.

The HBK system has been deployed on every single kilometer of GJ-owned classic line trackage since 1993, and has prevented countless possible speed-related accidents.

Currently, there is a program in place to convert both HBK and ATS-M into a system known as ATS-H. ATS-H would reprogram the HBK beacons and recievers to not only transmit speed control information, but to also warn about restrictive aspects, which ATS-M currently does. The system would replace the ATS-M beacons currently deployed and would save costs on broken ATS-M beaons, as the system approaches 90 years of age.

Driver Reminding Apparatus (DRA)

A DRA console in the cab of a locomotive. The DRA has been set, as the button is illuminated.

The DRA (Førermann Påminnelsemasjin/FPM) is a memory device used as an extra safety net aboard trains. Its use was mandated after the 1995 Ragnarfjord Train Crash, in which 30 people died because a driver passed a signal at danger after stopping within the safety overlap at a station platform (the signal head was not visible from the cab).

The DRA functions as a kill switch for traction on the train. It is a two-position switch, on and off. When the DRA is set, traction power is disconnected for the train. Railway regulations stipulate that the DRA must be set when shutting a train off, entering or exiting the cab, when the train has stopped for a signal at danger. The DRA may only be turned off when the train has authority to proceed (i.e. the signal clears), the driver has authority to turn on the train, or when the driver has been granted authority to pass a signal at danger by a shunting signal or by radio orders from dispatch.

Signage

Sign	Meaning
	Speed Limit; displayed in multiples of 10. In this case, 120 km/h.
	Junction Speed Limit; applies in the diverging route or track indicated.
	Advance Warning of Speed Limit; warns of a lower speed limit ahead, displayed in multiples of 10. In this case, 80 km/h.
	Advance Warning of Junction Speed Limit; warns of a lower speed limit ahead on a specified track, displayed in multiples of 10. In this case, 80 km/h.
	Advance Warning of a Temporary Emergency Speed Limit; displayed in multiples of 10. In this case, 30 km/h.
	Temporary Emergency Speed Limit; applies to all trains.
	End Temporary Emergency Speed Limit; applies to all trains.
	Raise Pantograph; The train must raise the pantograph and retract contact shoes.
	Lower Pantograph; The train must lower the pantograph and deploy contact shoes.
	Do Not Raise Pantograph; Despite the presence of overhead lines, do not raise the pantographs.
	Change In Current; The exact point where the change in current collection happens.
	Neutral Zone Advance Warning; There is a neutral zone in specified distance (meters).
	Long Neutral Zone Warning; The neutral zone ahead is of considerable length.
	Open Breakers; By this point circuit breakers must be open.
	Close Breakers; By this point circuit breakers must be closed.
	Current Indicator; Indicates the current type being used.
	End Current; The current of the specified type is ending.
	Whistle Board; The train must sound its horn or whistle when passing the sign.
	Close Air Vents; Reminder to the driver that a tunnel is approaching and they must close the air vents to avoid a pressure difference.
	Train All Stop; All trains, regardless of length or type, must stop at this sign.
	HHT Train Stop; HHT Trains must stop at the sign. The number indicates the number of trainsets that it applies to.
	Train Type Stop; Trains of the specified type(s) must stop at the sign.
	Train Car Stop; Trains of the car quantity specified must stop at the sign.
	AVK Begin; The track ahead is equipped with AVK, the system should exit standby mode.
	End AVK; The track ahead is no longer equipped with AVK, drivers are instructed to set the AVK to standby mode.
	Override ATS; The ATS transmitter is not aligned for the operating direction. Drivers have permission to override the signal.