SUBWAY SIGNALS

This is a listing of some of the more common signals found in the New York City subway system. If you find any not listed that you've seen while riding the front of a train, drop me an E Mail to Joe Korman and I'll add it to this Web Page.

INDEX to SIGNALS

AUTOMATIC SIGNALS
INTERLOCKING SIGNALS
IDENTRA
GRADE TIME
TRIP STOP
SIGNAL ATTRIBUTES - ASPECT & INDICATION
COMMUNICATIONS BASED TRAIN CONTROL (CBTC)
AUTOMATIC TRAIN SUPERVISON (ATS)
CONDUCTOR SIGNS AND SIGNALS

There are two major types of signals used in the subway -

AUTOMATIC SIGNALS

These signals are normally green and turn red after the FIRST CAR of the train the train passes it. Most of them have Green on top, Yellow in the middle and Red on the bottom. On some IRT lines the red and yellow are reversed.

Diagram showing how signals work with the red signals behind the train and the position of the stop arms.

Every signal has a number plate that contains identfying information. See the Chaining Page for information about these ID codes.

INTERLOCKING SIGNALS

These signals can be generally identified as having two sets of colored signal lights.

These signals control the movement of trains through track switches and are normally red. After the tower operator sets the track switches for the train, he/she clears the signal so the train may proceed.

All interlocking signals have a number plate like - The X denotes that this is an interlocking signal This signal is cleared by moving lever 14 to the LEFT.

Union Turnpike Interlocking machine (now out of service)

IDENTRA

IDENTRA was a switch control system that was used on the IRT Flushing line through at least the 1970's. Each cab at the ends of the train had a flat doughnut shaped antenna attached outside the car at the in front of the train operator cab. Inside the cab was a switch that allowed the operator to identify the train by express/local and destination.
The wayside was equipped with readers at the height of the antenna that read the code and set the switches and signals for the train. The towers could take control when needed in emergencies.
Automatic Train Supervision (ATS) is the 21st Century version of IDENTRA.

Other systems that used it included
the Broad St. Subway in Philadelphia,
the Chicago Transit Authoritry
and the Toronto Transit Commission.

The IDENTRA coil is seen in this shot of a Flushing train at Queensboro Plaza

GRADE TIME CONTROL

	In addition both of these signals may further be GRADE TIME CONTROL, in that they will not turn yellow or green until the train has slowed to a pre-determined speed. there are two types. The first (Y/S) is generally used on down grades where the train must be under a set speed for long length of track. As each signal clears to green, the next changes from red to Y/S. The second type is usually found at sharp curves, where once the train has slowed to the authorized speed, it may resume normal speed after leaving the curve.
	Station Time signals allow a following train, under the designated speed limit, to enter a station as the leading train leaves. All ST sections are preceeded by a ST speed limit sign. Some station time signals display the speed at which the train may move. Without ST signals, the following train would have to wait outside the station until the leading train has left the station.
	The aspect for PATH (former H&M) grade time signals is yellow/yellow, with the second yellow in a single lens head.

TRIP STOP

All signals have a "TRIP STOP" which is in the raised or "TRIPPING" position when the signal is RED. If the train operator tries to pass the signal the TRIP STOP will open a air valve called the "TRIP COCK" on the subway car's TRUCK (the TRUCK is the part of the car which holds the motors and wheels). The top of the tripper and the trip cock are painted yellow so that if they are engaged, there will be telltale strikemarks.

The open valve causes the train brakes to apply in EMERGENCY. The train brakes cannot be released again for about 20 seconds giving the train operator time to think about what he/she did wrong.

SIGNAL ASPECTS & INDICATIONS

Signals are said to have two atributes -

ASPECT

This is the color or combination of colors actually being displayed to the train operator.

INDICATION

This is the meaning of the signal to which the train operator must react.

To protect against malfunctioning signals displaying invalid or no aspects the RULE BOOK states that such signals are to be taken as its MOST restictive indication. That is, an automatic signal would be trated as a stop. An interlocking signal would be treated as a stop and stay.

AUTOMATIC & TIME SIGNALS

ASPECT	INDICATION
	Proceed
	Proceed with caution next signal is RED
	STOP radio for permission to pass
	Grade time signal - signal will turn green if train slows down next signal is RED. Usually used on a down grade for an extended length of track. These are sometimes called two shot timers, because there is alway a caution signal after the time signal that will clear to a timer if the train is under the speed limit.
	Grade time signal - signal will turn green if train slows down next signal is RED and the track switch is set for DIVERGING ROUTE.
	Grade time signal - usually used for a sharp curve where the train may get back to normal speed after passing the curve. This is sometimes called a one shot timer because there is onl;y one chance to get the train down to speed.
	The aspect for PATH (former H&M) grade time signals is yellow/yellow, with the second yellow in a single lens head.

INTERLOCKING SIGNALS

The top head usually denotes the condition of the track ahead and the bottom head tells what for which route the track switches are set. The switch routes are classed as MAIN or DIVERGING, however there is no consistancy as to which is which. The train operator must know what signal aspects to accept at each interlocking signal. Although I show the X L14 plate in red, the actual signs in use today are black on white. The white on red, used on the old IRT signals are more colorful though.
The original IRT interlocking signals were different in that each route controlled by a signal had its own head with G/R/Y (yes the IRT had the red in the middle) as needed. It was up to the train operator to kow which route was set up. A typical IRT signal might show R/R/Y meaning proceed with caution on the second diverging route. The PATH (former H&M) signals are similar. They are alway right hand route over the left hand route.

ASPECT	INDICATION
	Proceed on MAIN ROUTE
	Proceed with CAUTION on MAIN ROUTE
	Time signal MAIN ROUTE If a 'D' appears in place of the 'S', it is a time signal MAIN ROUTE and the next interlocking is set for DIVERGING ROUTE
	Proceed on DIVERGING ROUTE MAIN or DIVERGING On the BMT southbound at Dekalb Ave, before the reconstruction, a SB tunnel train had a BLUE lower head aspect for the bypass track. Green was to straight to Brighton and yellow was right to 4th Ave. At that time the SB trains were committed to branch after arriving in the station. Also the tunnel trains could bypass the station too. See DeKalb Ave for a track map.
	Proceed with CAUTION on DIVERGING ROUTE
	STOP AND STAY - call (radio or phone) for insructions if the signal does not clear after a few minutes.
	STOP, push "CALL ON" button, look at track switch for proper route and proceed prepared to stop in half of your range of vision. Pushing the CALL ON button causes the TRIP STOP to move to the clear position allowing the train to move past it. Since the CALL ON signal is displayed by the tower operator and accepted by the train operator both are responsible for moving the train.
	This is a Train Order Signal that is used to tell a train operator any special instructions, such as re-route, local to express switch, or wrong-rail through tunnel. The White lights mean there are no orders.
	This train order signal is telling the train operator to call 3111 for instructions. The telephone number is lighted as well as the red lights.
GAP FILLER Added at the suggestion of John H.
Gap fillers are used 14th St - Union Sq and South Ferry . The Gap Fillers extend out from the platforms to bridge the space between the platform and the car body and door at the curved stations. When the train stops on the detector circuit, the Gap Fillers extend and signal aspect turns red and is a Stop and Stay indication. After the train begins to move, the operator may not pass the GF signal until the red light is extinguished and the GF light is lit. The number or letter under the GF represent the track designation. In the samples below it is the for Track A of the two track South Ferry Loop. The South Ferry loop closed to regular passenger service on March 16, 2009, when the new station opened. See the Original station photos here.
	Stop and Stay. The Gap Filler is extended.
	Proceed, Gap Filler has retracted.
WHEEL DETECTORS
Wheel Detector signals were installed at interlockings in 1996. They are designed to further enforce the speed at which a train travels through an interlocking. Most are only active if the switch is set to the diverging route. The train must remain under the speed limit until the WD END sign is reached.
	Sign at the start of the wheel detector section
	Wheel detector off for your route. The switch is set for the main route.
	Wheel detector on for your route and the train speed is within the speed limit
	Wheel detector is active and the train is moving too fast. If the train doesn't slow down, the automatic stop arm will trip the train.
	End of the wheel detection area

COMMUNICATIONS BASED TRAIN CONTROL

COMMUNICATIONS BASED TRAIN CONTROL (CBTC) has been placed into service on the Canarsie L line in 2006. This technology uses laser diode signals to 'tell' each train how far ahead the leading train is. This allows for more trains per hour to be operated on the line. It is the signal system of the next generation. Both the trackways and the cars need special equipment to make CBTC fully workable. However, non-CBTC cars may operate in CBTC territory since the original signal system has been integrated into the system.

When the wayside hardware detects a CBTC train, it compares the train speed to those in front and back and signals to each the locations and allowable speed to all trains. Wayside signals flash the green light while a CBTC train is operating and the system recognizes the trains.

If the CBTC system on the train fails or the wayside equipment fails to detect the train the wayside signals revert to normal operation and control the railroad. If a non-CBTC train is on the line, the wayside signals control it and keep CBTC trains far enough behind it as if it were following the old signals.

Here are some articles about CBTC

Status Report June 2004
Other projects from Transportation Systems Design, Inc.

AUTOMATIC TRAIN SUPERVISON (ATS)

A new technology for the 21st Century is Automatic Train Supervision (ATS) and is installed on the mainline parts of the IRT (lines 1-6). This is a system that uses a transponder that signals to interlockings the route for a train setting the swtiches and clearing the signals. This appears to be related to the IDENTRA system used in many systems (including the IRT Flushing line) in the 1950's. Readers embedded between the rails read the transponder and set the switches and signals as the trains approach interlocking junctions. Information about each train's progress is also transmitted to the central control office database.
In August 2008, this system failed causing chaos on the IRT. Before the subway was restored to normal, each train operator had to call control to report their train ID and location.

CONDUCTOR SIGNALS and SIGNS

	Starting lights - three green lights along the ceilings at terminals controled by the dispatcher to indicate to the conductor to close the doors for the train to depart the terminal. Some terminals have a bell sounding in addition to the lights. In some terminals, the switch controlling the conductor starting lights in the dispatcher's, off also throws the track switch and sets the signal for that track.
	Holding lights - three yellow lights along the ceilings at intermediate stations controlled by the dispatcher to indicate to the conductor to hold the doors open. Used to make trains wait for connections or scheduled departure time from stations.
	Gap filler indicator - tells the conductor how many cars the gap filler system has detected. The doors must not be opened until the correct number of cars is displayed. Move mouse over the photograph to enlarge it. Click for full size photo in a new window.
	Conductor indciation board - tells the conductor that the train is properly positioned in the station to safely open the doors. There may be multiple boards for different length trains and types of equipment (R-40 vs R-143). Depending the on the type of cars, the conductor may be located in various cars. All cars up until the R-38, the conductor could be located in any cab. In the R-40 and R-42, the conductor could only be located in the married or #2 end of each car. In the subsequent cars the conductor could only be located in the end units of the ABBA and ABBB'A sets.