Railway Signals in Goyanes

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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 electronically signaled.

Modern signals in Goyanes use color-light technology, supplemented primarily by the Automatic Train Control (Automatisk Vagenkontroll - AVK) system.

Primary Color Light Signals

Signals in Goyanes use anywhere between two and six aspects. The color aspects are designed to be used in conjunction with the AVK system, however they can function independently of each other, i.e. signals without AVK can govern speed restrictions and AVK without signals operates just fine. AVK operates semi-independently of color signals on HHT lines, and on many secondary lines signals operate independently of AVK.

The primary types of signals in Goyanes are organized into two types: main signals (hovedsignalen) and distant signals (vørsignalen). Depending on the distance between track blocks, a main signal and a distant signal may be combined, however they can and often are separated.

Because in the Goyanean system more green lights means a more restrictive condition, it is not fail-safe and lamp proving circuits are used to ensure safe operating conditions.

Speed limits imposed by the color-lights only apply to trains without AVK equipment. Trains without AVK equipment follow the speed restrictions made by the signal or by posted signs beside the track. Trains with AVK equipment follow the speed directions of the AVK system, but use the color lights to determine the status of the track ahead.

Main Signal (Hovedsignalen) Aspects

Signal		Meaning	Notes
	Danger	The train must not pass the signal without permission from dispatch. Permission may come via radio or through a shunting signal allowing permittivity.	If authorization is given to pass a signal at danger, the speed limit is 30 km/h.
	Proceed 100	The train may proceed past the signal at a maximum of 100 km/h, posted sign speed, or at the speed AVK provides.	There is a safety overlap several meters in front of the signal, so the signal will change to red as it passes the signal.
	Caution 50	The train may proceed past the signal at a maximum of 50 km/h, posted sign speed (if lower) or at the speed AVK provides. The next signal is between 400 and 800 meters away and is at danger, the train must stop before the signal.	If the next signal is more than 800 meters away, this aspect will usually not display. Sometimes this signal will be used to slow trains down for a diverging route, or to mandate a speed restriction.
	Proceed 100, expect Danger	The train may pass the signal at 100 km/h, posted speed, or at the speed AVK provides. However, the next signal is at danger and the train must slow down and stop before it. Two-aspect signals can show Proceed 100, expect Danger with only one flashing green light (right image). This is somewhat of an oddity on the network.	The next signal is between 800 and 3000 meters away. If the next signal is more than 3000 meters away there will be a separate, freestanding distant signal.
	Proceed 100, expect Proceed 100	The train may pass the signal at 100 km/h, posted sign speed, or at the speed AVK provides. The next signal is also displaying a Proceed 100 aspect.
	Proceed 100, expect Caution 50	The train may pass the signal at 100 km/h, posted sign speed or at the speed AVK provides. However, the next signal is displaying a Caution 50 aspect, so the driver must slow down and expect to pass the signal at 50 km/h or the speed AVK authorizes.
	Caution 50, Short Block	The train may proceed past the signal at a maximum of 50 km/h, posted speed (if lower), or at the speed AVK provides. The next signal is less than 400 meters away and is at danger, the train must slow down immediately.	In some situations there is no next block, instead the line ends ahead, i.e. at a terminal station.

Distant Signal (Vørsignalen) Aspects

Freestanding distant signals as shown below are used when the next main signal is more than 3000 meters away. In such cases, the distant signal will be located at least 800 meters before the main signal it protects.

Signal		Meaning
	Expect Danger	The main signal is at danger. The train must slow down and be prepared to stop before the signal.
	Expect Proceed 100	The next signal is displaying Proceed 100.
	Expect Proceed 40	The main signal is showing Caution 50. The driver must slow down and expect to pass the signal at 50 km/h, a posted lower sign speed, or the speed AVK authorizes.

Shunting/Dwarf Signals

Shunting signals, also known as “dwarf signals” (kleinesignalen), are used for shunting purposes in yards, as well as for allowing permittivity of signals at danger such as at entrances to train station platforms to allow shunting or coupling of trains. 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 roadbed.

A Hovedkleinesignal at Hosen Sæg Stortoghass displaying "Danger"

There are also types of dwarf signals, called "Main Dwarf signals" (Hovedkleinsignalen) used as stand-ins for home signals in stations with a lot of shunting operations or where there are a lot of switches that need protection. In addition to the dwarf signal aspects given below, these signals also have a red light and may have two green ones (one for Caution 50, the other for Proceed 100).

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.
	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

An integrated speedometer/AVK display in a train cab displaying a 50 km/h limit decreasing to a 30 km/h limit, as seen by the green arrow range.

The AVK system was invented in 1922 after a Ministry of Transportation commission ruled that the consolidated four railways (Grand Trunk RR, Hysende-Osanhalt-Kongsland RR, The Hirendag Road, Nordstrom Seaboard RR) must install an automatic train stop technology on all trains if they wish to run above 100 km/h. The four railways convened to develop the technology, which was first tested in 1923. They came to the conclusion that not only could they stop the train, they could govern speeds using the cab displays. The way it functioned was by using track currents at either 100 Hz or 91.6 Hz (to avoid electrical interference on 3rd rail lines) to convey pulsating codes to a receiver mounted on the front of the train. The original AVK system used 4 codes, resulting in four basic speeds. They were “posted track speed,” 70 km/h, 50 km/h, and 30 km/h. This first edition was known as AVK-1, and was installed around the country to comply with the new regulations. The AVK system was updated with more codes to remove posted track speeds, and convey all speed information electronically, as well as integrating adaptive speed control into the mix. These iterations were known as AVK-2 and AVK-3.

How modern AVK (AVK-2, -3, -4H, -5H, and -6H) regulates the train is as follows: when the onboard computer receives the track code, the monitor inside the cab will show the new speed readout. On older systems, it would illuminate a bulb corresponding to the readout, on later systems it appears on a digital display. The computer, upon receiving the code, checks the train's speed against the new speed. If the speed is in violation, a warning tone sounds, and initiates a grace period. If braking does not commence in the grace period, the train applies a penalty brake automatically to bring the train into compliance. If the overspeed persists, the emergency brakes are applied.

In contrast, on AVK-1, there was no speed control, rather it was an advanced form of automatic train stop. If there was a change in restriction, whether positive or negative, the AVK would sound a tone, and if the driver did not acknowledge in a certain timeframe, the emergency brakes were applied.

In the 1960s as the Høyhastikettog (HHT) high-speed trains were being developed, a new AVK generation was devised to create common functionality and safety. This was known as AVK-4H, the H standing for HHT. The system relies on overlay pulse codes at 250 Hz current, which augment the existing 100/91.6 Hz codes to create even more code availability. AVK-4H was installed on most lines and trains by the 1970s.

In 1985, with the widespread adoption of digital computing, AVK-5H was introduced. AVK-5H uses computer stations both lineside and aboard the train to take into account more factors such as braking gradients, train set performance, track geometry, and more to more accurately adjust speeds for trains. In addition AVK-5H and -4H pulse codes remained the same, it was more an upgrade to the computing infrastructure both on the train and lineside.

In recent years, AVK-6H has been developed for use on the HHT system. As speeds increased to 360 km/h, new pulse codes were developed in both the 100/91.6 Hz range and in the 250 Hz range to allow even higher speeds. So far, AVK-6H is only installed on HHT trains capable of >320 km/h and on tracks capable of such speeds. It has full backwards compatibility with -5H to ensure interoperability.

Currently, AVK-4H, -5H and -6H are the most common systems of AVK in use, however usage of -4H is limited to conventional lines, while -5H and -6H are found on high-speed lines, and several dedicated lines. It is installed on most passenger trains in the GJ system, but many freight trains do not have it, and instead rely on the color-light signal aspects for speed regulation.

AVK is failsafe at all generations, as the absence of a pulse code gives a 30 km/h speed limit readout. On lines without AVK, the system can be overridden. The system remains on in a standby state though, and at the first detection of new code, will activate again. Track codes that exceed a train's design speed are nulled out to the highest possible speed for the train by the onboard AVK reciever to ensure safe operation.

AVK Pulse Codes

100/96.1 Hz code	250 Hz code	Cab Signal Speed	Notes
0	0	30 km/h	Original AVK Code. Failsafe State.
75	0	50 km/h	Original AVK Code.
75	75	70 km/h	Original AVK Code. Remapped starting with AVK-4H.
96	0	100 km/h	Original AVK Code, "Posted Speed." Valued at 100 with AVK-2.
96	96	130 km/h	Introduced on AVK-2, Remapped with AVK-4H.
120	0	160 km/h	Introduced on AVK-2, Remapped with AVK-4H.
120	120	200 km/h	Introduced on AVK-3, Remapped with AVK-4H.
180	0	240 km/h	Introduced on AVK-4H.
180	180	270 km/h	Introduced on AVK-4H.
270	0	280	Introduced on AVK-5H.
270	270	300 km/h	Introduced on AVK-5H
420	0	320 km/h	Introduced on AVK-6H
420	420	360 km/h	Introduced on AVK-6H.