Pittsburgh & Lake Erie Railroad
Historical Society

Dedicated to the preservation of materials regarding the
Pittsburgh & Lake Erie Railroad,
its predecessors, subsidiaries and affiliates.

Terms and Definitions

The information contained on this page was compiled from the
Pittsburgh and Lake Erie Railroad Transportation Department
Operating, Air Brake and Safety Rules
Effective July 1, 1975



Block—A length of track of defined limits, the use of which by trains and engines is governed by block signals.

Absolute Block—A block in which a train of engine is not permitted to enter while it is occupied by another train or engine except as prescribed by the rules.


Automatic Block Signal System (ABS)—A block signal system wherein the use of each block is governed by an automatic block signal.

Manual Block Signal System (MBS)—A block signal system wherein the use of each block is governed by block signals controlled manually upon information by telephone or other means of communication.

Traffic Control System (TCS)—A block signal system under which train movements are authorized by block signals whose indications supersede the superiority of trains for both opposing and following movements on the same track.


Division—That portion of the railroad assigned to the supervision of the Superintendent.

Branch—That portion of a division designated by timetable.


Interlocking—An arrangement of signals and signal appliances so interconnected that their movements must succeed each other in proper sequence and for which interlocking rules are in effect. It may be operated manually or automatically.

Interlocking Limits—The tracks between the extreme opposing home signals of an interlocking.


Route—The course or way which is, or is to be, traveled.

Conflicting Route—Two or more routes, opposing, converging or intersecting, over which movements cannot be made simultaneously without possibility of collision.


Fixed Signal—A signal of fixed location indicating a condition affecting the movement of a train or engine.
NOTE—The definition of a "Fixed Signal" covers such signals as switch target, train order, block, interlocking, speed signs, stop signs, yard limit signs, or other means for indicating a condition affecting the movement of a train or engine.

Indication—The information conveyed by a signal as viewed from the direction of an approaching train.

Block Signal—A fixed signal, or hand signal in the absence of a fixed signal, at the entrance of a block to govern trains and engines in entering and using that block.

Approach Signal—A fixed signal used to govern the approach to another signal.

Home Signal—A fixed signal at the entrance to a route or block to govern trains or engines entering and using that route or block.

Interlocking Signal—The fixed signals of an interlocking.

Dwarf Signal—A low home signal.

Signal Mast—The upright to which a signal is directly attached.

Dummy Mast—A short upright, displaying a blue light or reflector, placed on top of a bracket post, or bracketed to the side of a signal mast, to show there is a track between the bracket post or signal mast, and the track for which signals are provided.

Bracket Post—An upright with a crosspiece on top of which is placed one or more masts.

Rear of a Signal—The side of the signal from which the indication is received.

Advance of a Signal—The side of the signal opposite to that from which the indication is received.


Normal Speed—The maximum authorized speed.

Limited Speed—Not exceeding 45 miles per hour.

Medium Speed—Not exceeding 30 miles per hour.

Reduced Speed—Prepared to stop short of train or obstruction.

Slow Speed—Not exceeding 15 miles per hour.

Restricted Speed—proceed prepared to stop short of train, obstruction or switch not properly lined; looking out for broken rail and not exceeding 15 miles per hour.


Station—A place designated in the timetable by name.

Block Station—A place provided for the blocking of trains by block signals or other means.

Interlocking Station—A place from which an interlocking is operated.

Control Station—A place from which remote control signal appliances or switches are operated.

Control Point (CP)—A location where signals and/or other functions of a traffic-control system are controlled from the control machine.


Electrically Locked Switch—A hand-operated switch equipped with an electrically controlled device which restricts the movement of the switch.

Spring Switch—A switch equipped with a spring mechanism arranged to restore the switch points to normal position after having been trailed through.


Timetable—The authority for the movement of regular trains subject to the rules. It contains classified schedules with special instructions relating to the movement of trains and engines.

Schedule—That part of a timetable which prescribes class, direction, number, and movement for a regular train.


Main Track—A designated track upon which trains are operated by timetable, train order, or both, or the use of which is governed by block signals.

Single Track—A main track upon which trains are operated in both directions.

Two or More Tracks—Two or more main tracks upon any of which the current of traffic may be in either specified direction.

Current of Traffic—The movement of trains on a main track in one direction, specified in the timetable.

Secondary Track—A designated track upon which trains or engines may be operated without timetable authority, train orders or block signals.

Running Track—A track designated in the timetable upon which movements may be made subject to prescribed signals and rules, or special instructions.

Siding—A track auxiliary to a min or a secondary track for meeting or passing trains.

Controlled Siding—A siding the use of which is governed by signals under the control of a train dispatcher or operator.

Yard—A system of tracks within defined limits provided for making up of trains, storing of cars and other purposes, over which movements not authorized by timetable, or by train order, may be made, subject to prescribed signals and rules, or special instructions.


Track Car—A self propelled car with or without trailers which may be manually moved to or from the track. The term "Track Car" shall include other self propelled units, such as: Burro Cranes, Highway Rail Cars, Detector Cars, Weed Burners, Tie Tampers, and other similar equipment. This type equipment may not operate signals or shunt track circuits.


Train—An engine or more than one engine coupled, with or without cars, displaying a marker.

Regular Train—A train authorized by a timetable schedule.

Passenger Train—A train scheduled to carry passengers .

Extra Train—A train not authorized by a timetable schedule. It may be designated as:
     Extra—for any extra train except passenger extra or work extra;
     Passenger Extra—for passenger train extra;
     Work Extra—for work train extra.

Superior Trains—A train having precedence over another train.

Train of Superior Right—A train given precedence by train order.

Train of Superior Class—A train given precedence by timetable.

Train of Superior Direction—A train given precedence in the direction specified by timetable as between opposing trains of the same class.


Train Register—A book or form at designated stations for registering trains, the time of arrival and departure of trains and such other information as may be prescribed.