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quadrant variety. Those of the lower quadrant variety would most often have two positions, but three roundels, with two being of the more restrictive color. This 60-75 degree lower quadrant, three aperture design of semaphore spectacle was known as the "Continuous Light
Spectacle" and predates the Loree-Patenall patented, three position upper quadrant spectacle of 1902. The intent was to reduce the chance of a malfunction or snowfall causing the signal to only partially rise towards the horizontal, yet still displaying the most restrictive color night indication. Color images of these signals bear this out as the "Red-Red-Green" of the home and "Yellow-Yellow-Green" of the distant arms were universal used on 60 and 75 degree (B&M, Central Vermont) L.Q. semaphores. There were no three color 60 or 75 degree signals used. The "standard" 90 degree 3 position Lower Quadrant spectacle saw limited application (the last were used in Memphis, Tenn. and St. Louis, Mo,. Terminals) as the Lorre-Patenall U.Q. spectacle provided significantly greater visual range.
1345:- This class of signals is displayed for trains moving into a block where a track circuit has been de-energized or does not exist. A "shunted" track circuit indicates either the block is occupied by another train or railcar, or there is a problem such as a broken rail or flooded track. Where a track is not protected by track circuits that track must be presumed to be occupied. As the name implies this signal requires trains to move at Restricted speed, specifically with the ability to stop short of an obstruction. Restricted speed signals take many forms including Restricted and Restricted Proceed (ARA Rule 290, see Figure) where trains must simply pass the signal at restricted speed and also Stop and Proceed (Rule 291), where a train must come to a complete stop before proceeding at restricted speed. Stop and Proceed has fallen out of favor with most freight railroads due to the fuel and time savings of allowing the trains to not come to a complete stop. This aspect class can be displayed on almost all railroads in North America.
559:
1311:- Block aspects convey basic track occupancy information and advise the engineer (operator) which of the basic signal rules (common to all railroads) he/she is to follow in the operation of his/her train at any point on the railway line. These include Clear (ARA Rule 281, see Figure), Advance Approach and Approach (Rule 285) which instruct the engineer to "expect no stop", "expect stop at second signal" and "expect stop at next signal" respectively. Advance approach is only used in situation with short signal blocks to ensure trains have enough stopping distance. These are the most common signal aspects in North America and are the only aspects most automatic block signals need to display.
582:
Earlier types of electro-pneumatic semaphores made by US&S had seen some limited application by 1880 as automatic block signals. The need to maintain air pressure in the long pneumatic lines eventually led the railroads to discontinue their widespread use as automatic block signals. However, these types did see long service in interlocking plants. Early semaphores also had limited range with manual wire operation and poor reliability in bad weather. Thus some railroads continued to use disc signals where automatic block signal operation was needed between manual block stations as borne out by period rule books well into the 1920s and beyond.
834:
1053:(B&O) railroad, circa 1918. He also developed a proprietary signal aspect system to replace the earlier A.H. Rudd, ARA standard signaling system (PRR-based) then in use. The CPL system was unique in that it was a conceptually original design instead of being an update of an existing system. The CPL system incorporates several design principles that are otherwise unique to North American signaling. Use of the color red only in the case of an absolute stop or restricted speed situation is the most significant characteristic. The other 11 standard possible combinations do not display a red aspect.
25:
1294:
1027:
280:
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were worked mechanically, pneumatically to give restricting-type signals as did mast type signals at interlockings, but motorized dwarfs were more common after the development of the Model 2A signal in 1908. As early as 1915, the technological push by -such intellectual giants as A.H. Rudd of the
Pennsylvania R.R. and his concept of speed signaling combined with his development of the Position Light signal and the concurrent color-light signals using William Churchill's doublet lens combination in practical terms made the semaphore technically obsolete.
775:
1042:
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lens giving the indications in multiple-head interlocking signals in a fixed location with regard to the mast and the other signal heads, this not being the case with multiple-lens color light signals. In time the costs of the significantly more expensive searchlight signal's relay began to outweigh the savings from its compact size and single bulb when compared with the simple multiple-lens color light signal. By the end of the 1980s the searchlight had lost its position as the most popular signal style in North
America.
825:-inch (140 mm) switch lamp lenses (often of Macbeth manufacture) instead of the otherwise standard inverse-convex and stepped lens type found in the standard inner-doublet design. The Union version was later updated to a single unit akin to the GRS model. As modular color light signals have become widespread, target-type configurations have been typically offered alongside vertical type configurations. The triangular color light signal was especially useful in physically restricted and confined areas.
906:
693:
1339:- These combine functions of a "Diverge to" signal with an "Approach Speed" signal and occur in areas of complex trackwork where there are no intermediate signals between one interlocking and the next. In the United States only a few combination signals like Medium Approach Medium, Medium Approach Slow and Diverging Approach Medium/Slow are ever found in rulebooks and not frequently used in practice. The Canadian standard rulebook contains signal rules and aspects for every possible combination.
1317:- When a train needs to be told to slow down due to dynamic conditions an "Approach Speed" aspect is used. These inform the engineer to slow to a prescribed speed by the next signal. The most common reason for this is that the train is to take a diverging, or non-Normal speed route at the next interlocking. Signals of this type include Approach Medium (ARA Rule 282, see Figure), Approach Limited, Approach Slow (Rule 285) and Approach Diverging. These signals are typically displayed on the
1078:
1182:
1327:- This class appears only on absolute signals and informs the engineer that the train will be taking a diverging route and need not expect a stop at the next signal. In speed signaling the engineer is informed of the speed the train needs to take the route at, in weak route signaling the engineer is just informed of a diverging route. Signals in this class include Medium Clear (ARA Rule 283, see Figure), Slow Clear (Rule 287), Limited Clear and Diverging Clear.
522:) require that dark or obscured signal heads be treated as displaying their most restrictive aspect (i.e. stop), but fault-tolerant aspect design can help the engineer take a safer course of action before the failure of a signal becomes apparent. While not all aspects are fault-tolerant, the green lamp on the topmost head is only used by the least restrictive signal aspect, "Clear," so there is no case where a failure could accidentally display a clear aspect.
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1168:
226:
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1351:- Stop signals are displayed on Absolute signals, in fact the ability to display an absolute Stop is part of that signal type's definition. Stop is the most important signal as passing a signal at Stop presents a serious risk of accident. Engineers committing a Stop signal violation automatically have their Federal certification suspended and are frequently fired. Stop signals can only be passed upon special permission from a control authority.
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block, and red/lunar white representing a restricting indication, meaning the engineman was permitted to enter his train into an occupied block. The individual marker lamps provide speed information, 12 o'clock being Normal speed, 6 being Medium speed (Limited speed if flashing), 10 being Normal to Medium (Limited if flashing), 2 being Normal to Slow, 8 being Medium to Medium, 4 being Medium to Slow and no lit markers being Slow to Slow.
861:
the modular light, where each lamp was an independent unit capable of being arranged into a signal of arbitrary configuration, including triangular. US&S has a popular single case type with its styles R/R-2, P-2/5 and N, while GRS offered their triangularly arranged Type G, with the
Chicago Signal Company providing a similar version. Today's Safetrans Triangular is a copy of the GRS Type G but with vertically arranged double doors.
632:
1375:
1418:, be marked with a "D" placard. The placard is intended to remind engineers that they are bound by a 40 mph (64 km/h) speed restriction, and must approach the interlocking signal prepared to stop, whenever a station stop is made or train speed drops below 10 mph (16 km/h) in the approach block. The restrictions hold until the interlocking signal is clearly visible and is displaying a "proceed" indication.
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especially where bi-directional running was implemented, signals needed to be mounted above the track or on bracket masts to allow this right hand placement. As locomotive design changed to allow good visibility on both sides of the track, regulations were changed allowing railroads to shift to bi-directional mast type signals, using signal bridges only in special situations involving multiple tracks or restricted views.
720:. He had finished developing color standards for railroad glassware, which Corning had patented on October 10, 1905. They were immediately put to use as daylight short-range and tunnel-type electric incandescent-bulb illuminated signals. He then turned his attention to medium- and long-range daylight signals using the same incandescent electric lamps with greatly improved optics: the "Doublet-Lens" combination.
746:-inch-diameter (270 mm) stepped outer lens. This revolutionary development provided a signal with a visible indication of over 1 mile (1.6 km) from the signal in broad daylight, when the signal was located on tangent track. The early color light signals were visible for only about half that distance (2,500 feet or 760 metres) while using about the same electrical current, then a major concern in "
271:, which helps improve signal visibility in bright ambient lighting. Target designs vary, but are usually round or oval, depending on the layout of the signal lamps. For each type of signal there are usually a range of target dimensions that can be chosen by the individual railroad company. As dwarf signals are not designed to be seen from long distances, they are not generally equipped with targets.
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497:- Used for trains entering or operating in unsignaled territory or when entering a de-energized track circuit. Regulatory definition of no greater than 20 miles per hour (32 km/h) outside interlocking limits, 15 mph within interlocking limits. Trains operating at restricted speed must be able to stop within half vision short of any obstruction, and must look out for broken rails.
958:"sail" effect of the inordinately large and tombstone shaped background of the four-light variant. The original installation made use of lamps positioned in front of a free standing black sheet-iron backing, but shortly thereafter, the new circular background was fitted to the then reduced 3 lamp per row device and directly to the backing on a framework referred to as a "spider."
1425:
103:. Speed signaling transmits information regarding how fast the train is permitted to be going in the upcoming segment of track; weak route signaling transmits information related to the route a train will be taking through a junction, and it is incumbent upon the engineer to govern the train's speed accordingly. Weak route signaling is applied with the term
264:
so-called "virtual heads" to save on space and cost. This is where a dwarf signal displays multiple lamps on what would ordinarily be a single signal head creating the effect of multiple signal heads. For example, a stack of dwarf lamps in the order yellow, red, green can display plain yellow, red and green as well as yellow over green and red over green.
80:
uncommon to see a single railroad operating many different types of signaling inherited from predecessor railroads. This variety can range from simple differences of hardware to completely different rules and aspects. While there has been some recent standardization within railroads in terms of hardware and rules, diversity remains the norm.
485:- Original concept for a standard "reduced" speed normally set to 30 miles per hour (48 km/h) and can range as high as 40 miles per hour (64 km/h). This is the typical speed for diverging movements through interlockings and is also the speed trains are limited to when approaching a Stop or Restricted Proceed-type signals.
586:
1898, the US&S Style "B" semaphore, the first successful low voltage, entirely enclosed mechanism electric motor semaphore appeared. It was revolutionary, improving on all earlier semaphore designs, with the last such example being taken out of service as recently as 2009 on the former
Siskiyou line of the S.P., now CORPS.
180:. Their most restrictive aspect is "stop" and trains cannot pass them at stop unless they obtain special authority. Absolute signals will default to displaying stop unless expressly cleared by a control authority. In older practice, multiple signal heads are directly above and below each other on the mast.
1762:
Emergency Order No. 20, Notice No. 2 (1996-03-05). "Commuter and
Intercity Passenger Railroads, Including Public Authorities Providing Passenger Service, and Affected Freight Railroads; Clarification of Emergency Order Requiring Enhanced Operating Rules and Plans for Ensuring the Safety of Passengers
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on what was known as a "Z" armature which was wound with copper magnet wire. When the coil was energized, the wire hoops were moved away from the large glass opening in the front of the wooden "banjo" case exposing its white-painted interior. The colored glass disc at the same time moving away from a
896:
series of films. These extended signal shades improves visibility in bright sunny conditions and blocks other light from other sources that could illuminate and provide a false aspect to the engineer. The shades also provide an unintended bonus of helping to focus the light to be more noticeable from
754:
In the UK, original electromechanical searchlight signals consisted of a low-power incandescent bulb mounted behind a semaphore spectacle devoid of a blade behind a target. The Union Switch and Signal
Company searchlight signal ubiquitous to the United States has an internal cable with weights system
324:
Dwarf signals are typically mounted on the ground in areas of low speed movements or restricted clearances. Dwarf signals may be sometimes mounted higher up on a small mast or other structure for improved visibility. These can be known as "high dwarfs" or "stick signals," but a tall mounting does not
957:
as an effort to reduce the maintenance required by semaphore signals as well as visibility problems caused by the new overhead electrification project. The original system used rows of four lights. The system was later reduced to use rows of three lamps, surrounding a common center. This reduced the
876:
along with many others: D&RG, etc. The GRS units used a smaller "background" than the comparable US&S vertical possibly somewhat compromising long range visibility. Today the most popular type of new signal in North
America is a modular design manufactured by Safetran, as it is the cheapest,
860:
Development of the doublet lens by
Churchill at Corning Glass Works allowed an electric light source to be more effective than with previous daytime colorlight signal designs. There are two main types of cases: the single case, where two or more lamps were contained within a single cast housing, and
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to concentrate the output of up to four light sources behind a single lens. However, other than as low-speed signals requiring only short-range visibility, these have not been entirely successful and most are now being removed from mainline service after a relatively short working life. Capable of
707:
The 1911 patenting of the "Doublet-Lens" combination for long range (2,500 ft or 760 m in daylight) by Dr. William
Churchill at Corning Glass's research facility in Corning, New York, indicated the reign of the semaphore signal in railroad use was rapidly approaching its end. By 1916, this
593:
Semaphore signals have been almost completely replaced by light signals in North America, but they contain several important design elements. The overwhelming majority of semaphore type signals used in North America, and the only type surviving in service as of 2009 are of the three position, upper
320:
Prior to 1985, signals were required by regulation to be mounted above and to the right of the track they governed. This mounting was designed to allow the engineer to view the signal when driving a steam or diesel locomotive with a long hood that restricted the view to the left. In most situations,
115:
ran speed signaling, while railroads in the west used route signaling, with some mixing of systems in the Midwest and South. This was due to the lower train density in the west combined with generally simpler track layouts. Over time, the route signaling railroads have incorporated segments of speed
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and in the collections of a very few railroad enthusiasts. These include signals that were manufactured by US&S, GRS, Hall and even the Federal Signal Company. The Hall Company's 1924-introduced variant of the dwarf "Position Color Light" signal (or "PCL" as they were referred to at that time)
1073:
for restricting also being present in some installations. The main head is surrounded by up to 6 markers at the 12:00, 2:30, 4:30, 6:00, 8:30 and 10:30 o'clock positions. The function of the main head was block occupancy information with green representing two or more clear blocks, yellow one clear
1005:
it became standard practice to add these red lenses to high position lights and even some pedestal signals. The Norfolk and Western modified its signals to use red and green lenses in the upper head Stop and Clear positions and yellow lenses everywhere else. In the 1980s Amtrak modified most of its
589:
The motor-controlled North American semaphores used since the advent of the track circuit block system of 1872, provided a form of automation sought after by the railroads to reduce labor costs and improve reliability over manually operated systems as in the UK, Germany and elsewhere. Dwarf signals
190:
which detect the presence of trains or obstructions automatically. Automatic signals are permissive with their most restrictive aspect being one of the "restricted proceed" variety. Trains can pass an automatic signal displaying "restricted proceed" without any outside permission. Automatic signals
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The all-metal US&S Enclosed Disc Signal was introduced in 1896 and had one version that employed both a red and a green banner (as well as both colored glasses) that were mechanically arranged in such a way as to have the banners and glass roundels exchange places within the signal case as the
880:
Modular color lights allow for all the cost savings inherent in color lights, but also make it easier for railroads to stock signals and perform alterations to interlockings. Instead of having to order custom heads, new modules can be taken from stock to build new signals or modify existing heads.
811:(GRS) Type "G" design consisted of a cast iron box containing three doublet lens units in a triangular arrangement. The US&S "TR" and "TP" models used three smaller connected single-lamp housings with a common background. The long defunct Chicago Signal Company had a version that used standard
758:
Searchlight signals' use became widespread mostly due to their relatively low maintenance, high visibility, low power-consumption, and after 1932 using a compound lens with a 4-watt 3-volt bulb that worked quite well in territory with battery-powered signaling. Also of significance was the single
263:
are smaller signals used in low-speed or restricted-clearance areas. Most signaling aspect systems have a parallel set of aspects for use with dwarf signals that differ from aspects used in high signals. Dwarf signals may have multiple heads just like a high signal, but sometimes dwarf signals use
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A standard high position light consists of two heads; the bottom head can remain dark unless it is needed. In addition to the high position light signals the PRR developed a dwarf position light, as with many railroads, these dwarf signals are also referred to as a "pot," a tradition carried over
848:
Vertical color light signals are the second major pattern of color light signals, and today represent the most popular form of signal in North America, supplanting the searchlight. These signals are not different from the triangular type color signal in function, but present a much altered visual
581:
By the end of the 19th century, particularly as trains became longer and faster, and railroad lines grew more congested, the banjo signal was considered to have a single and terminal flaw: visibility. The internal disc was difficult to see in foggy weather and when snow clung to the glass panel.
244:
mounted roughly in a vertical stack, each head capable of displaying one to four different aspects. Automatic signals are identified with a number plate whereas absolute signals are not. The signal's aspect is based on a combination of the aspects each individual head displays. Where a signal has
79:
There is no national standard or system for railroad signaling in North America. Individual railroad corporations are free to devise their own signaling systems as long as they uphold some basic regulated safety requirements. Due to the wave of mergers that have occurred since the 1960s it is not
1137:
in the 1830s. The railroad then developed a more effective system consisting of wooden balls, painted red, white or black, and hoisted up or down a pole on a rope-and-pulley system. The initial use of these signals was merely to indicate the on-time status of trains, rather than to control train
1017:
systems. Today most of the old PRR position lights are slowly being replaced by modern color lights, but Amtrak, SEPTA and the LIRR continue to install new position lights (Amtrak's being of the colorized variety). US&S no longer manufactures position light equipment, but updated models from
585:
By the early 1890s more railroads began installing electric motor-operated semaphore signals, which were visible at distances of thousands of feet, during the day and under inclement weather conditions. In 1893 the high voltage, electric motor automatic block signal semaphore made its debut. By
1301:
Most North American railroads have between 10 and 20 separate signal rules, each which are often represented by multiple aspects. However, all of these complicated rules revolve around the simple premise of informing the locomotive engineers how they are to operate their train in the present
611:
The color of the semaphore frequently matches the above categories as well, with absolute signals typically having a white stripe on a red blade and the others having a black stripe (most often repeating the shape of the blade's end) of either square or 60 degree, were the RSA Standard.
386:- When on a signal doll post, indicates intervening track between the signal and the track to which the signal applies, or to indicate all equipment on the section of track to the rear of the blue signal is absolutely not to be moved as men are working under, on, or in said equipment.
308:
are arranged with multiple signals are mounted on the same masts governing two adjacent tracks. Bracket masts tend to be the tallest type of signal to allow the train crew to see the signal over a train on the intervening track. Signals in electrified territory may be mounted on the
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combination to directionally focus their small power out over a long range (3,500 ft or 1,100 m in daylight.) New LED signals may either use an unfocused array or act as a drop-in replacement behind a traditional lens. U.S. signal lenses have a standard diameter of
973:
mounted step sides outwards) with a portion of the lens steps painted black. A light yellow tinted conical glass with frosted tip was chosen, as this color was determined to have the highest visibility under fog conditions based on empirical studies at Corning at that time.
852:
Continuing problems with reliable, long range light sources from a single, optical colored lens and a focused bulb restricted the first use of color light signals to short range daytime exterior applications, or tunnels and other underground or low speed complexes. The 1911
1758:"Commuter and Intercity Passenger Railroads, Including Public Authorities Providing Passenger Service, and Affected Freight Railroads Emergency; Order Requiring Enhanced Operating Rules and Plans for Ensuring the Safety of Passengers Occupying the Leading Car of a Train."
380:- Used to indicate a full stop or other restrictive condition, or used as a "placeholder" light (when that part of a signal is unused but to confirm to the crew the signal is working, so as not to require guessing the rest of the combination in case of a light failure).
877:
with all of the four major Class 1 railroads installing it almost exclusively. Today, both GRS and Safetran market separate modular systems for high and dwarf signals, while US&S uses the single modular Style "R-2" design for high and Style N-2 for dwarfs.
1285:
are among the most rare and sought after by collectors, as are the extremely rare mechanical dwarf semaphores of the T. George Stiles Company. These signals were installed at the beginning of the 20th century by the New Haven Railroad and used into the 1980s.
197: – Semi-automatic signals are those that typically act as an automatic signal, but can be set to display an absolute "stop" aspect. Semi-automatic signals do not have a number plate, but can display an explicit "restricted proceed"-type signal.
791:
Triangularly arranged color light signals consist of a cluster of three color lamp sockets in the middle of a large circular target. They were one of the first widely used type of high intensity color light signal, notably adopted by the New York Central and
1227:
A banjo-shaped wooden case housed a large iron wire hoop with red silk stretched and glued over it. The opposite end had a much smaller hoop in which a very thin disc of colored glass was secured. This entire iron wire assembly was pivoted inside an
426:
Individual signal heads may be set to flash a color to create a different signal aspect. Signals in the United States typically flash only one head at a time, while signals in Canada may flash two heads at a time; flashing lights are generally less
287:
position light signal bridge with replacement mast signals in the background. The design of steam locomotives meant that all signals had to be placed to the right of the running track. Current diesel engine design allows both left- and right-hand
574:(US&S) introduced an electro-pneumatic design in 1881. This was more reliable than earlier, purely mechanical versions, and more railroads began to use them. At that time, however, they were considerably more expensive than
1413:
from forgetting that they were approaching a stop signal after making a station stop. The resulting "Delay in Block Rule" requires that all distant signals, located in territory where push-pull trains operate in the absence of
360:
inches (210 mm). North American signals use a standard set of colors, defined in October 1905, and which became common to other modes of transportation as shown on page 384 of the Simmons-Boardman 1911 Signal Dictionary.
107:
because some speed signal aspects may be used in the system and also because exact route information is not typically conveyed, only the fact of a diverging or straight route, each having a predictable range of known speeds.
1302:
location, and what they are to expect at the next signal location. From here the large set of rules and aspects can be broken down into a small number of classes which are common to all North American signaling systems:
750:
territory". By 1925, the development of "high-transmission colors" of railroad glassware by Gage and Corning Glass improved this limited distance to an acceptably competitive 3,500 feet (1,100 m) on tangent track.
532:
Some signaling logic incorporates "bulb out" (lamp failure) or other fault detection, to attempt to display the most restrictive aspect in case of a fault. However, this feature is not required nor universally adopted.
993:, which was one-third-owned by the PRR. US&S was the sole supplier of classic position light equipment as this manufacturer's factory was formerly located on the four track mainline of the P.R.R. in Swissvale, Pa.
723:
Hall's response to this situation was to buy the 1918 filed patents from one Mr. Blake for his "Searchlight" signal. In reality, the searchlight signal was an updated and modernized variation of the old Hall enclosed
2195:
491:- 15 miles per hour (24 km/h) while within the limits of an interlocking and 20 mph when not in the limits of an interlocking. This is used for trains negotiating complex trackwork at interlockings.
871:
Over time, due to its low cost and versatility, the modular color light signal became the standard in North America. The first modular system was the GRS Type "D", first marketed in 1922, and adopted by the
1156:
used vane signals mounted on wooden towers. Painted boards (vanes) of various colors were moved into position to signify danger (stop), caution, and safety (proceed). The vanes were illuminated at night by
1056:
The CPL consists of a central position target with up to four pairs of doublet lens units around the perimeter of the background disc. The lens units are spaced at 45-degree axes using the positions: green
996:
In 1954, the PRR experimented installing red lenses in the horizontal position of the upper head to help increase the at distance visibility of absolute Stop signals at Overbrook interlocking. Under the
1333:- Same as above only the train can expect to stop at the signal after the interlocking. These signals include Medium Approach (ARA Rule 286, see Figure), Slow Approach (Rule 288) and Diverging Approach.
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to realize their just-introduced and most advanced Style "L" semaphore mechanism (the very last produced by any U.S. signal company) was indeed obsolete. That dual-lens device had been developed by
1224:
The Hall disc signal (also called a "banjo" signal) was the first electrically operated signal to be widely adopted by American railroads. Thomas Hall patented his disc signal design in 1867.
897:
far distances. This shade was originally adopted by the Union Pacific and Denver Rio Grand and Western railroads to prevent snow buildup on one shade from obscuring the signal lens above it.
1260:
systems, initially utilizing line wire circuits, running on poles alongside the tracks, connecting the track treadle devices. One of the earliest such systems was installed in 1871 on the
1365:"Super Clear" signal that allows passage to the next interlocking with a fixed signal and also the "Cab Speed" signal that informs the engineer to proceed under direction of cab signals.
191:
are typically recognized by having an attached number plate and in older practice, having multiple signal heads offset from each other on the mast (i.e., on opposite sides of the mast).
978:
from the 19th century revolving "Pot Type Signal." Four plain white lamps are able to display four low-speed aspects each with two lamps. In 1930, close clearances of the Philadelphia
570:
Semaphore signals were first developed in England in 1841. Some U.S. railroads began to install them in the early 1860s, and semaphores gradually displaced other types of signals. The
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four aspects, most examples had two lamp units simultaneously light red to give the most restrictive indication greater visual range than obtained with the use of a single lamp unit.
732:, add a miniature spectacle and Pyrex, low-expansion Borosilicate glass roundels, and couple that with a very efficient elliptical reflector and optical lens system with a very large
1112:
As of 2008 and as with all U.S. railroads, CSX is slowly replacing all of the remaining CPLs on its system with contemporary vertical color light LED signals. The signals on the old
941:-inch-diameter (140 mm) lamps to simulate the positions of an upper quadrant semaphore blade. Position lights were developed by A.H. Rudd, Superintendent of Signalling of the
2393:
292:
Signals are most commonly mounted on trackside masts about 12 to 15 feet (3.7 to 4.6 m) high to put them in the eyeline of the engineer. Signals can also be mounted on
762:
To overcome the issues of associated with moving parts, new solid-state, single-lensed signals were developed. The first such product, marketed in 1968 as the "Unilens" by
965:
bulb mounted in front of a parabolic mirror that increases the relatively weak bulb's intensity. To avoid phantom indications the design makes use of a special inverted
1120:
terminals. The sole exception is the Staten Island Railroad, which recently upgraded its signaling system with new CPLs using modern Safetran position light equipment.
864:
Signals like the model N/N-2 could also be mounted directly on the ground as a dwarf signal without a backing. The most notable user of this type of signal was the
607:
Semaphores with a "fishtail" end (that is, a V-notch end) are "distant" signals conveying to the engineer what the aspect of the next signal is (as a forewarning).
83:
This article will explain some of the aspects typically found in North American railroad signaling. For a more technical look at how signals actually work, see
604:
Those with a pointed end are "permissive" signals and permit a train to continue at a significantly lower speed rather than having to come to a complete stop.
510:. Aspects are often designed so that a faulty or obscured lamp will cause the resulting aspect to be more restrictive than the intended one. Operating rules (
558:
1138:
movements. The wooden balls were often configured with lanterns for nighttime use. Ball signals were first used to direct train movements in 1852, on the
525:
Where a signal aspect incorporates a flashing lamp, the flashing lamp is always applied to less restrictive signals. This is to prevent a stuck flashing
479:(switches). This speed is defined by individual railroads and ranges anywhere from 40 miles per hour (64 km/h) to 60 miles per hour (97 km/h).
857:
project was one example of this type of color light signal, with an outer colored 8 3/8" optical lens, some of which are still in service as of 2011.
1010:, these are not to be confused with color position lights described below, which while functionally similar are structurally considerably different.
653:
148:
all use a strong system of speed signaling in Canada, but have some segments of route signaling on lines they have acquired in the United States.
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1134:
2555:
1361:
is employed without fixed trackside automatic signals, special signal aspects are required at absolute signals. These include some sort of
173:
2150:
2060:
1845:
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A 4 feet (1.2 m) disc, painted red and mounted on a revolving pole; it indicated "stop" when positioned to face an approaching train.
2140:
2085:
1725:
76:
of track conditions so that they may keep their train under control and able to stop short of any obstruction or dangerous condition.
1181:
1006:
former-PRR position lights to use the equivalent color light colors in all of the positions of both heads. Internally referred to as
374:- Used to warn the engineer of an impending stop or speed reduction for an occupied "block" ahead. Also used for low-speed movements.
982:
complex spurred development of the pedestal-type position, which consisted of two position dwarf signals in a common cast backing.
2413:
2050:
884:
Modular color light signals are often fitted with a full-length sun shade often called "Vader Hoods" by railroad employees and
1195:
2408:
2367:
1634:
563:
416:(The AAR's official name) - Used in position light systems as an all-purpose high visibility color, greatest fog penetration.
2565:
2560:
2210:
1943:
458:
Signal rules and aspects make use of several pre-defined speeds. These speeds are also used in Weak Route type signaling.
601:
Those with a square end are "absolute" signals and generally force trains to stop when in their most restrictive position.
2205:
2155:
2125:
2398:
1885:
438:
systems utilize just two signal lamp colors (lunar white for proceeding and red for a full stop); examples include the
2130:
2504:
2499:
2388:
1522:
679:
314:
2100:
661:
2357:
1838:
1261:
84:
19:
2175:
2423:
2403:
1402:
1139:
136:
use speed enhanced route signaling (or what by now is effectively speed signaling with some route elements), and
2225:
2190:
1986:
657:
401:
116:
signaling through merger and have also adopted more speed-based aspects into their systems. Of the five major
2454:
2439:
1895:
1398:
1233:
clear primitive Fresnel lens at the top of the case which was backed up on the rear side of the case with a
2115:
1905:
1667:
1265:
1106:
1591:
833:
2509:
1880:
1831:
1246:
1049:
The color position light (CPL) signal was developed by Frank Patenal, superintendent of signaling of the
865:
28:
1555:
1149:
A pivoted board, called a "smashboard", which could be operated to swing into position across the track.
881:
With simple bracketry, even triangular color lights may be built up with these standardized components.
392:- Obsolete. Up to around 1940, purple lenses were used rather than red as the "Stop" indication in some
140:
uses a mix of speed and route signaling based on the original owner of the line. Commuter railroads and
2519:
2484:
2474:
2464:
2459:
2449:
2080:
1910:
1094:
439:
410:- Blue filtered light to eliminate all trace of yellow used to indicate a restricted proceed condition.
230:
69:
2514:
2469:
2372:
2230:
2075:
2027:
1875:
1870:
1167:
1474:
1321:
to an interlocking, but can sometimes be used with short signal blocks in place of Advance Approach.
621:
2524:
2494:
2489:
2479:
2444:
2362:
2170:
2095:
2001:
1963:
642:
571:
553:
475:- A speed less than Normal Speed that was employed starting in the 1940s for use with higher speed
1237:. The disc signal was first placed into service in 1870 on the New York and New Haven Railroad at
2529:
2327:
2312:
2070:
2042:
1862:
1592:"Harrisburg Division-East; "Overbrook" Interlocking Station and Jeff & Valley Interlockings."
1453:
873:
646:
304:
and masts typically provide at least 20 feet (6.1 m) of clearance over the top of the rail.
32:
2307:
2297:
2246:
2165:
2160:
1890:
1307:
1257:
1093:(a B&O subsidiary) in the 1920s, and deployed system-wide shortly thereafter. Parts of the
1026:
946:
808:
597:
The blade portion of the semaphore was of several designs, each conveying a different meaning:
301:
24:
1767:
1293:
1097:
received CPLs later, when the B&O gained control of that line. In the 1980s both Amtrak's
2534:
1968:
1958:
1920:
1915:
1238:
1098:
1090:
1082:
986:
950:
942:
854:
284:
202:
112:
1541:
1510:
2090:
1733:
422:- Plain incandescent white light. Used in dwarf position light signals with frosted lenses.
279:
8:
2317:
2200:
1692:
1680:
1253:
1035:
990:
921:
841:
793:
774:
717:
709:
1709:
186: – Automatic signals are governed by logic connected through electrical
1930:
1854:
1554:
Pennsylvania Railroad Technical & Historical Society, Philadelphia Chapter (2008).
1448:
1050:
801:
713:
145:
1819:
Mobile CROR Signal App. Can be used as a tool to help learn Canadian Railroad signals.
1611:
1133:
The first signals employed on an American railroad were a system of flags used on the
2352:
2256:
2032:
1651:
1630:
1518:
697:
334:
1013:
New PRR type position lights continued to be installed up until the 1980s on former
2418:
2347:
2322:
2302:
2120:
1757:
1153:
1041:
979:
755:
to mechanically align the signal in the red position if there is a system failure.
443:
177:
137:
117:
44:
generally fall into the category of multi-headed electrically lit units displaying
1577:
1116:
have also been almost entirely replaced as have many of the CPL dwarfs at the two
945:(PRR). They were introduced in 1915 as a replacement for semaphore signals on the
1406:
1281:
985:
PRR type position lights were used throughout the vast PRR system as well as the
708:
optical combination and a flagging sales response prompted the management of the
507:
447:
217:, road crossings, etc. These are much less common than the three standard types.
1795:
905:
2145:
1991:
1978:
1801:
Pennsylvania Railroad (1968). "Rules for conducting transportation." 1968-04-28
1443:
1362:
1318:
1113:
542:
476:
310:
40:
692:
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2332:
2220:
2022:
1430:
1358:
1242:
1234:
1229:
729:
435:
214:
187:
129:
121:
95:
There are two main types of signaling aspect systems found in North America,
1394:
as the signal block before the interlocking is known as the approach block.
2266:
2110:
2017:
1948:
1900:
1410:
1280:
There are examples of various mechanical and electrical signals in several
1077:
998:
970:
954:
767:
747:
342:
206:
169:
144:
all use speed signaling where they own or maintain the tracks they run on.
73:
2292:
728:. What Blake had done was to harness the standard railroad three-position
245:
multiple heads, aspects are read from top to bottom and are described as "
1953:
962:
889:
428:
210:
1211:
404:
ruled that purple should no longer be used in the U.S. for that purpose.
2342:
2215:
2180:
1938:
1415:
966:
225:
1515:
Trains and Technology: The American Railroad in the Nineteenth Century
913:
2251:
1823:
1379:
893:
393:
337:
running off of low voltage DC current or, more recently, high output
1763:
Occupying the Leading Car of a Train With Appropriate Amendments."
1297:
American Railway Association Signal Aspects Revision of October 1910
1109:
installed dwarf CPLs to replace earlier signals in those terminals.
631:
2337:
2261:
1374:
763:
701:
2282:
2185:
1812:
1785:
Armstrong, John (1957). "All About Signals." Two-article series.
1142:. Other mechanical signals used during the 19th century include:
1117:
1014:
1002:
885:
797:
168: – Absolute signals are usually connected to an
2287:
2135:
2105:
917:
397:
317:
lines may be mounted back-to-back on the same mounting device.
209:
signals or signals governing special safety appliances such as
141:
1382:
light rail. Note the 'D' boards placed in accordance with the
909:
A Pennsylvania Railroad high signal displaying Approach Medium
868:, but units could be found on railroads all over the country.
2065:
1786:
1753:
U.S. Federal Railroad Administration (FRA), Washington, D.C.
1383:
1123:
1102:
779:
526:
515:
1818:
2055:
1558:
Based on the original article by Edward Waytel. 2008-10-28.
1275:
1045:
A CPL dwarf signal on CSX at Bailey interlocking, Baltimore
838:
519:
511:
236:
North American signals generally follow a common layout. A
133:
1424:
1188:
A smashboard installation on the approach to a swingbridge
506:
Signal aspects are designed to incorporate some degree of
1796:"Canadian Railway Operating Rules - CROR Signal Aspects."
1666:
New Haven Railroad Historical and Technical Association.
1031:
338:
325:
change the lower speed applications of the dwarf signal.
125:
465:- The normal speed for the railroad line, also known as
333:
Electric signal lamps are typically low power (35 watt)
1685:
1241:, using a track treadle device to activate it, as the
961:
Each position lamp unit is equipped with a 12 volt, 6
1268:). About 1500 disc signals were operational by 1896.
1420:
161:
North American signals are commonly of three types.
1756:Emergency Order No. 20, Notice No. 1 (1996-02-20).
267:Behind the signal head is placed a dark backing or
786:
696:An example of a one-head searchlight signal on a
2547:
1679:American Railway Association, New York (1922).
1517:. Cranbury, NJ: Associated University Presses.
1135:Newcastle and Frenchtown Turnpike and Rail Road
828:
1726:"Canadian Railway Telegraph History – Signals"
837:Hooded GRS Type D modular color lights on the
716:'s William Churchill, while he was working at
1839:
1668:"New Haven Railroad Historical Events (p.4)."
1369:
1288:
151:
2151:Interoperable Communications Based Signaling
1701:
1472:
1466:
1081:B&O CPL signal displaying yellow on the
2086:Automatic Train Protection (United Kingdom)
1504:
1502:
1500:
1498:
1496:
1494:
1128:
660:. Unsourced material may be challenged and
90:
1846:
1832:
1124:Obsolete mechanical and electrical signals
622:Railway signal § Colour light signals
328:
31:color position lights on bracket masts at
1508:
1390:Distant signals are often referred to as
900:
796:railroads, and later used exclusively by
680:Learn how and when to remove this message
1643:
1606:
1604:
1602:
1600:
1511:"Volume 4. Bridges and Tunnels; Signals"
1491:
1373:
1292:
1276:Extant mechanical and electrical signals
1210:
1076:
1040:
1025:
912:
904:
832:
778:Target style color light signals on the
773:
691:
557:
529:from accidentally upgrading the signal.
278:
224:
23:
2051:Advanced Civil Speed Enforcement System
1707:
1624:
1572:
1570:
1568:
1566:
1564:
1475:"Discussions on Blue and Purple Lenses"
1021:
2571:Railway signaling in the United States
2548:
1853:
1618:
1256:installed the disc signals as part of
725:
615:
575:
368:- Used to indicate "clear" or proceed.
229:A stacked searchlight dwarf signal at
2211:Train Protection & Warning System
1827:
1813:Railroad Signaling and Communications
1681:"The Invention of the Track Circuit."
1597:
1578:"Pennsy and N&W Style PL Signals"
1536:
1534:
1378:A pair of distant signals on the NJT
564:Atchison, Topeka and Santa Fe Railway
2556:Rail transportation in North America
1944:Integrated Electronic Control Centre
1694:American Practice in Block Signaling
1649:
1561:
1219:
658:adding citations to reliable sources
625:
547:
68:types, each displaying a variety of
2206:Train automatic stopping controller
2126:Continuous Automatic Warning System
1714:. New York: Locomotive Engineering.
1697:. New York: Railroad Gazette. 1891.
1556:"PRR Position Light Signal System."
1089:This CPL was first deployed on the
1030:A full B&O-style CPL signal on
1018:Safetran continue to be available.
927:Position light signals use rows of
341:arrays. Incandescent signals use a
13:
1886:Communications-based train control
1531:
989:(LIRR), a PRR subsidiary, and the
501:
14:
2582:
1806:
888:due to the appearance similar to
572:Union Switch & Signal company
536:
1473:Todd Sestero, ed. (2019-02-14).
1423:
1245:was not developed until 1872 by
1194:
1180:
1166:
630:
85:North American railway signaling
20:North American railway signaling
2368:Westinghouse Brake & Signal
2131:ContrĂ´le de vitesse par balises
1997:North American railroad signals
1747:
1718:
1673:
1660:
1403:Federal Railroad Administration
1140:New York and New Haven Railroad
201:Other types of signals include
156:
2226:Transmission balise-locomotive
2191:Sistema Controllo Marcia Treno
2101:Automatische treinbeĂŻnvloeding
1987:Application of railway signals
1711:Block and Interlocking Signals
1629:. MBI Publishing. p. 55.
1590:Penn Central Railroad (1972).
1584:
1548:
1542:""Tri-Light" Railroad Signals"
1509:Bianculli, Anthony J. (2003).
1202:Vane signal mounted on a tower
787:Triangular color light signals
576:Hall disc, or "banjo", signals
402:Interstate Commerce Commission
1:
2176:Punktförmige Zugbeeinflussung
1896:European Train Control System
1459:
1399:1996 Maryland train collision
920:colorized position lights at
2116:Chinese Train Control System
1906:Radio Electronic Token Block
1650:King, Everett Edgar (1921).
1612:"B&O CPL Signals - RSUS"
1405:amended its regulations for
1107:Chicago Northwestern Station
829:Vertical color light signals
7:
2566:Railway signaling in Mexico
2561:Railway signaling in Canada
1881:Centralized traffic control
1594:Signal diagram. 1972-01-01.
1479:Railroad Signals of the U.S
1437:
274:
111:Typically railroads in the
29:Baltimore and Ohio Railroad
10:
2587:
2081:Automatic train protection
1778:
1370:Distant (approach) signals
1289:Common signal rule classes
1095:Chicago and Alton Railroad
619:
562:A semaphore signal on the
551:
540:
440:Baltimore Metro SubwayLink
313:structure, and signals on
300:spanning multiple tracks.
231:Springfield, Massachusetts
152:Common signaling practices
17:
2432:
2381:
2373:Westinghouse Rail Systems
2275:
2239:
2231:Transmission Voie-Machine
2076:Automatic train operation
2041:
2028:Track circuit interrupter
2010:
1977:
1929:
1876:Automatic block signaling
1871:Absolute block signalling
1861:
1034:at Carroll interlocking,
453:
240:consists of one to three
220:
2171:Pulse code cab signaling
2096:Automatic Warning System
2002:Railway semaphore signal
1964:Solid State Interlocking
1656:. New York: McGraw-Hill.
1397:In the aftermath of the
1129:Early mechanical signals
554:Railway semaphore signal
467:Maximum Authorized Speed
91:Signaling aspect systems
52:. Signals may be of the
2071:Automatic train control
1708:Elliott, W. H. (1896).
1625:Solomon, Brian (2003).
1454:Signalling block system
1343:Restricted Speed Signal
329:Signal colors and lamps
33:Magnolia, West Virginia
2247:Level crossing signals
2166:Positive Train Control
2161:Linienzugbeeinflussung
1891:Direct traffic control
1387:
1386:"Distant Signal Rule".
1298:
1258:automatic block signal
1216:
1091:Staten Island Railroad
1086:
1046:
1038:
924:
910:
901:Position light signals
845:
809:General Railway Signal
783:
704:
567:
289:
233:
128:uses speed signaling,
35:
1969:Westlock Interlocking
1959:Rail operating centre
1921:Train order operation
1916:Track Warrant Control
1792:, June and July 1957.
1409:operation to prevent
1377:
1355:Cab Signaling Signals
1296:
1272:indication required.
1239:Stamford, Connecticut
1214:
1099:Chicago Union Station
1083:Staten Island Railway
1080:
1044:
1029:
1008:position color lights
987:Long Island Rail Road
969:(i.e. a single clear
943:Pennsylvania Railroad
916:
908:
855:New York Penn Station
836:
777:
695:
561:
285:Pennsylvania Railroad
282:
228:
113:Eastern United States
27:
2091:Automatic train stop
1670:Accessed 2011-10-12.
1411:locomotive engineers
1247:Dr. William Robinson
1022:Color position light
730:polarized vane relay
654:improve this section
431:than steady lights.
101:weak route signaling
66:color position light
50:weak route signaling
1736:on October 11, 2004
1337:Combination Signals
1254:Hall Signal Company
1036:Baltimore, Maryland
991:Norfolk and Western
922:Trenton, New Jersey
866:Chesapeake and Ohio
794:Seaboard Coast Line
718:Corning Glass Works
710:Hall Signal Company
616:Searchlight signals
203:train order signals
74:locomotive operator
1931:Signalling control
1855:Railway signalling
1627:Railroad Signaling
1449:Railway signalling
1388:
1299:
1266:Boston & Maine
1217:
1174:Wooden ball signal
1087:
1069:and a lunar white
1051:Baltimore and Ohio
1047:
1039:
925:
911:
846:
802:New Jersey Transit
784:
714:Cornell University
705:
568:
335:incandescent lamps
290:
234:
213:, non-interlocked
146:Canadian railroads
36:
2543:
2542:
2353:Smith and Yardley
1815:- photos and info
1765:Federal Register,
1653:Railway Signaling
1636:978-0-7603-1360-2
1315:Approach at Speed
1220:Hall disc signals
874:Southern Railroad
698:Canadian National
690:
689:
682:
548:Semaphore signals
118:Class 1 railroads
72:which inform the
2578:
2419:Transport Canada
2303:General Electric
2240:Crossing signals
2121:Cityflo 650 CBTC
2043:Train protection
1848:
1841:
1834:
1825:
1824:
1772:
1751:
1745:
1744:
1742:
1741:
1732:. Archived from
1730:www.trainweb.org
1722:
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1489:
1488:
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1485:
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1433:
1428:
1427:
1392:approach signals
1325:Diverge to Clear
1262:Eastern Railroad
1215:Hall disc signal
1203:
1198:
1189:
1184:
1175:
1170:
1154:Reading Railroad
1072:
1068:
1064:
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980:Suburban Station
940:
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823:
819:
816:
745:
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737:
685:
678:
674:
671:
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634:
626:
495:Restricted Speed
444:Washington Metro
359:
358:
354:
351:
298:cantilever masts
178:train dispatcher
172:controlled by a
138:Norfolk Southern
41:railroad signals
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2011:Train detection
2006:
1973:
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1407:push-pull train
1372:
1331:Diverge to Stop
1308:Automatic Block
1291:
1282:railway museums
1278:
1222:
1209:
1208:
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748:primary battery
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735:
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651:
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508:fault tolerance
504:
502:Fault tolerance
456:
448:PATCO Speedline
400:. In 1952, the
356:
352:
349:
347:
331:
277:
223:
159:
154:
97:speed signaling
93:
39:North American
22:
12:
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5:
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2535:United Kingdom
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2146:Integra-Signum
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1992:Cab signalling
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1807:External links
1805:
1803:
1802:
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1780:
1777:
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1773:
1771:
1770:
1768:61 FR 8703-06.
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1583:
1560:
1547:
1530:
1523:
1490:
1464:
1463:
1461:
1458:
1457:
1456:
1451:
1446:
1444:Cab signalling
1439:
1436:
1435:
1434:
1371:
1368:
1367:
1366:
1363:absolute block
1352:
1346:
1340:
1334:
1328:
1322:
1319:distant signal
1312:
1290:
1287:
1277:
1274:
1221:
1218:
1206:
1205:
1200:
1193:
1191:
1186:
1179:
1177:
1172:
1165:
1162:
1161:
1160:
1159:
1158:
1150:
1147:
1130:
1127:
1125:
1122:
1114:Alton Railroad
1023:
1020:
902:
899:
830:
827:
788:
785:
688:
687:
638:
636:
629:
620:Main article:
617:
614:
609:
608:
605:
602:
552:Main article:
549:
546:
543:Railway signal
541:Main article:
538:
535:
503:
500:
499:
498:
492:
486:
480:
470:
455:
452:
424:
423:
417:
411:
405:
387:
381:
375:
369:
330:
327:
315:bi-directional
302:Signal bridges
294:signal bridges
276:
273:
222:
219:
199:
198:
195:Semi-automatic
192:
188:track circuits
181:
174:block operator
158:
155:
153:
150:
92:
89:
62:position light
18:Main article:
9:
6:
4:
3:
2:
2583:
2572:
2569:
2567:
2564:
2562:
2559:
2557:
2554:
2553:
2551:
2536:
2533:
2531:
2528:
2526:
2523:
2521:
2518:
2516:
2513:
2511:
2508:
2506:
2505:North America
2503:
2501:
2498:
2496:
2493:
2491:
2488:
2486:
2483:
2481:
2478:
2476:
2473:
2471:
2468:
2466:
2463:
2461:
2458:
2456:
2453:
2451:
2448:
2446:
2443:
2441:
2438:
2437:
2435:
2431:
2425:
2422:
2420:
2417:
2415:
2412:
2410:
2407:
2405:
2402:
2400:
2397:
2395:
2392:
2390:
2387:
2386:
2384:
2382:Organisations
2380:
2374:
2371:
2369:
2366:
2364:
2361:
2359:
2356:
2354:
2351:
2349:
2346:
2344:
2341:
2339:
2336:
2334:
2333:Progress Rail
2331:
2329:
2326:
2324:
2321:
2319:
2316:
2314:
2311:
2309:
2306:
2304:
2301:
2299:
2296:
2294:
2291:
2289:
2286:
2284:
2281:
2280:
2278:
2276:Manufacturers
2274:
2268:
2265:
2263:
2260:
2258:
2255:
2253:
2250:
2248:
2245:
2244:
2242:
2238:
2232:
2229:
2227:
2224:
2222:
2221:Trainguard MT
2219:
2217:
2214:
2212:
2209:
2207:
2204:
2202:
2199:
2197:
2194:
2192:
2189:
2187:
2184:
2182:
2179:
2177:
2174:
2172:
2169:
2167:
2164:
2162:
2159:
2157:
2154:
2152:
2149:
2147:
2144:
2142:
2139:
2137:
2134:
2132:
2129:
2127:
2124:
2122:
2119:
2117:
2114:
2112:
2109:
2107:
2104:
2102:
2099:
2097:
2094:
2092:
2089:
2087:
2084:
2082:
2079:
2077:
2074:
2072:
2069:
2067:
2064:
2062:
2059:
2057:
2054:
2052:
2049:
2048:
2046:
2044:
2040:
2034:
2031:
2029:
2026:
2024:
2023:Track circuit
2021:
2019:
2016:
2015:
2013:
2009:
2003:
2000:
1998:
1995:
1993:
1990:
1988:
1985:
1984:
1982:
1980:
1976:
1970:
1967:
1965:
1962:
1960:
1957:
1955:
1952:
1950:
1947:
1945:
1942:
1940:
1937:
1936:
1934:
1932:
1928:
1922:
1919:
1917:
1914:
1912:
1909:
1907:
1904:
1902:
1899:
1897:
1894:
1892:
1889:
1887:
1884:
1882:
1879:
1877:
1874:
1872:
1869:
1868:
1866:
1864:
1863:Block systems
1860:
1856:
1849:
1844:
1842:
1837:
1835:
1830:
1829:
1826:
1820:
1817:
1814:
1811:
1810:
1800:
1797:
1794:
1791:
1789:
1784:
1783:
1769:
1766:
1761:
1759:
1755:
1754:
1750:
1735:
1731:
1727:
1721:
1713:
1712:
1704:
1696:
1695:
1688:
1682:
1676:
1669:
1663:
1655:
1654:
1646:
1638:
1632:
1628:
1621:
1613:
1607:
1605:
1603:
1601:
1593:
1587:
1579:
1573:
1571:
1569:
1567:
1565:
1557:
1551:
1543:
1537:
1535:
1526:
1524:0-87413-803-5
1520:
1516:
1512:
1505:
1503:
1501:
1499:
1497:
1495:
1480:
1476:
1469:
1465:
1455:
1452:
1450:
1447:
1445:
1442:
1441:
1432:
1431:Trains portal
1426:
1421:
1419:
1417:
1412:
1408:
1404:
1400:
1395:
1393:
1385:
1381:
1376:
1364:
1360:
1359:cab signaling
1356:
1353:
1350:
1347:
1344:
1341:
1338:
1335:
1332:
1329:
1326:
1323:
1320:
1316:
1313:
1310:
1309:
1305:
1304:
1303:
1295:
1286:
1283:
1273:
1269:
1267:
1263:
1259:
1255:
1250:
1248:
1244:
1243:track circuit
1240:
1236:
1235:kerosene lamp
1231:
1230:electromagnet
1225:
1213:
1197:
1192:
1183:
1178:
1169:
1164:
1163:
1155:
1151:
1148:
1145:
1144:
1143:
1141:
1136:
1121:
1119:
1115:
1110:
1108:
1104:
1100:
1096:
1092:
1084:
1079:
1075:
1054:
1052:
1043:
1037:
1033:
1028:
1019:
1016:
1011:
1009:
1004:
1000:
994:
992:
988:
983:
981:
975:
972:
968:
964:
959:
956:
952:
948:
944:
923:
919:
915:
907:
898:
895:
891:
887:
882:
878:
875:
869:
867:
862:
858:
856:
850:
843:
840:
835:
826:
810:
807:The original
805:
803:
799:
795:
781:
776:
772:
769:
765:
760:
756:
752:
749:
731:
727:
721:
719:
715:
711:
703:
699:
694:
684:
681:
673:
670:February 2024
663:
659:
655:
649:
648:
644:
639:This section
637:
633:
628:
627:
623:
613:
606:
603:
600:
599:
598:
595:
591:
587:
583:
579:
577:
573:
565:
560:
555:
544:
534:
530:
528:
523:
521:
517:
513:
509:
496:
493:
490:
487:
484:
481:
478:
474:
473:Limited Speed
471:
468:
464:
461:
460:
459:
451:
449:
445:
441:
437:
436:rapid transit
432:
430:
421:
420:(Plain) White
418:
415:
412:
409:
406:
403:
399:
395:
391:
388:
385:
382:
379:
376:
373:
370:
367:
364:
363:
362:
344:
340:
336:
326:
322:
318:
316:
312:
307:
306:Bracket masts
303:
299:
295:
286:
281:
272:
270:
265:
262:
261:Dwarf signals
258:
256:
252:
248:
243:
239:
232:
227:
218:
216:
212:
208:
204:
196:
193:
189:
185:
182:
179:
175:
171:
167:
164:
163:
162:
149:
147:
143:
139:
135:
131:
130:Union Pacific
127:
123:
122:United States
119:
114:
109:
106:
102:
98:
88:
86:
81:
77:
75:
71:
67:
63:
59:
55:
51:
47:
43:
42:
34:
30:
26:
21:
16:
2363:Union Switch
2267:Wayside horn
2111:Catch points
2018:Axle counter
1996:
1949:Interlocking
1901:Moving block
1787:
1764:
1749:
1738:. Retrieved
1734:the original
1729:
1720:
1710:
1703:
1693:
1687:
1675:
1662:
1652:
1645:
1626:
1620:
1586:
1550:
1514:
1482:. Retrieved
1478:
1468:
1396:
1391:
1389:
1354:
1348:
1342:
1336:
1330:
1324:
1314:
1306:
1300:
1279:
1270:
1251:
1226:
1223:
1132:
1111:
1088:
1055:
1048:
1012:
1007:
999:Penn Central
995:
984:
976:
971:Fresnel lens
960:
955:Philadelphia
926:
883:
879:
870:
863:
859:
851:
849:appearance.
847:
842:TN Pass Line
806:
790:
768:fiber optics
761:
757:
753:
722:
706:
676:
667:
652:Please help
640:
610:
596:
592:
588:
584:
580:
569:
537:Signal types
531:
524:
505:
494:
488:
483:Medium Speed
482:
472:
466:
463:Normal Speed
462:
457:
433:
425:
419:
414:Lemon Yellow
413:
407:
389:
383:
377:
371:
365:
343:doublet lens
332:
323:
319:
305:
297:
293:
291:
268:
266:
260:
259:
254:
250:
246:
241:
237:
235:
211:slide fences
207:manual block
200:
194:
183:
170:interlocking
165:
160:
157:Signal types
110:
104:
100:
96:
94:
82:
78:
65:
61:
57:
53:
49:
45:
38:
37:
15:
2525:Switzerland
2500:New Zealand
2495:Netherlands
2201:Slide fence
1954:Lever frame
1798:2010-02-01.
1416:cab signals
1349:Stop Signal
1264:(later the
963:candlepower
890:Darth Vader
726:disc signal
429:restrictive
408:Lunar White
238:high signal
58:color light
54:searchlight
46:speed-based
2550:Categories
2433:By country
2216:Train stop
2181:RS4 Codici
1939:Block post
1740:2023-09-24
1484:2020-07-05
1460:References
1001:and later
967:toric lens
489:Slow Speed
2440:Australia
2293:AŽD Praha
2252:Crossbuck
2156:Crocodile
1380:RiverLINE
1157:lanterns.
1061:, yellow
947:Main Line
894:Star Wars
782:main line
700:track in
641:does not
184:Automatic
2530:Thailand
2338:Safetran
2328:Magnetic
2313:Griswold
2262:E-signal
1790:Magazine
1438:See also
1357:- Where
949:between
886:railfans
764:Safetran
702:Winnipeg
477:turnouts
446:and the
311:catenary
275:Mounting
166:Absolute
2475:Germany
2465:Finland
2450:Belgium
2445:Bavaria
2348:Siemens
2323:Hitachi
2298:Federal
2283:Adtranz
2186:SelTrac
2033:Treadle
1979:Signals
1779:Sources
1118:Chicago
1015:Conrail
1003:Conrail
936:⁄
892:in the
820:⁄
798:Conrail
766:, uses
741:⁄
662:removed
647:sources
566:in 1943
398:derails
355:⁄
288:siting.
215:sidings
120:in the
70:aspects
2520:Sweden
2515:Poland
2510:Norway
2480:Greece
2470:France
2455:Canada
2358:Thales
2288:Alstom
2257:Wigwag
2136:EBICAB
2106:Balise
1788:Trains
1633:
1521:
1401:, the
1085:, 2018
1065:, red
918:Amtrak
469:(MAS).
454:Speeds
442:, the
434:A few
390:Purple
372:Yellow
269:target
221:Layout
142:Amtrak
2490:Japan
2485:Italy
2460:China
2394:AREMA
2343:Saxby
2196:SACEM
2141:IIATS
2066:ATACS
1911:Token
1384:NORAC
1103:Metra
951:Paoli
780:SEPTA
527:relay
516:NORAC
394:yards
366:Green
253:over
249:over
242:heads
64:, or
2414:IRSE
2409:HMRI
2318:Hall
2061:ASFA
2056:ALSN
1631:ISBN
1519:ISBN
1252:The
1152:The
1101:and
953:and
839:DRGW
800:and
645:any
643:cite
520:CROR
512:GCOR
396:and
384:Blue
134:BNSF
132:and
105:weak
99:and
2424:UIC
2404:FRA
2399:ERA
2389:AAR
2308:GRS
1105:'s
1032:CSX
656:by
518:or
378:Red
339:LED
296:or
257:".
176:or
126:CSX
48:or
2552::
1728:.
1599:^
1563:^
1533:^
1513:.
1493:^
1477:.
1249:.
804:.
734:10
578:.
514:,
450:.
283:A
205:,
124:,
87:.
60:,
56:,
1847:e
1840:t
1833:v
1743:.
1639:.
1614:.
1580:.
1544:.
1527:.
1487:.
1071:\
1067:—
1063:/
1059:|
938:8
934:3
931:+
929:5
844:.
822:8
818:3
815:+
813:5
743:2
739:1
736:+
683:)
677:(
672:)
668:(
664:.
650:.
357:8
353:3
350:+
348:8
255:Z
251:Y
247:X
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
