Deerfield & Roundabout Railway Engineering Data
(Revision 01-02-2008)
DEFINITIONS OF TERMS RELATING TO TRACK WORK
Written or complied by Jeffrey G. Hook
Note: The Deerfield and Roundabout Railway definitions are based primarily on those originally published by the American Railway Engineering Association, circa 1940. A number of original A.R.E.A. definitions are not included and others have been modified in order to provide for their practical application to the Deerfield and Roundabout Railway. A.R.E.A. definitions that have been modified for the Deerfield and Roundabout Railway are indicated by (D&R) after the name of the definition. Definitions written specifically for the Deerfield and Roundabout Railway are indicated by (D&R only) after the name of the definition. A.R.E.A. definitions that do not apply to the Deerfield and Roundabout Railway, but are included for comparison purposes, are indicated by (AREA only) after the name of the definition. Definitions without a qualifier after the name indicate an original A.R.E.A. definition that is applicable to the Deerfield and Roundabout Railway. A number of definitions are also included from the tenth edition of The Track Cyclopedia, 1985, the Dictionary of Railway Track Terms, 2003, and The Pennsylvania Railroad Specifications for Standard Track, 1932. These are indicated by either (TTC) or (RTT) or (PRR) respectively after the name of the definition.
GENERAL TERMS
ALIGNMENT - The horizontal location of a railway track with reference to curves and tangents.
BRANCH LINE - The secondary line or lines of a railway.
BALLAST (TTC) - Selected material placed on the roadbed for the purpose of holding the track in line and surface.
CLOSURE RAILS - The rails between the parts of any special trackwork layout, as the rails between the switch and the frog in a turnout (sometimes called Lead Rails or Connecting Rails); also the rails connecting the frogs of a crossing or of adjacent crossings, but not forming parts thereof.
COMPROMISE RAIL - A relatively short rail the two ends of which are of different sections, corresponding with the sections of the rails which are to be joined; it provides a transition from one section to a different rail section.
COMPROMISE JOINT, RAIL - A Joint for uniting the abutting ends of contiguous rails of different sections, or of rails of the same section but which have different joint drillings.
CONNECTING TRACK - Two turnouts with the track between the frogs arranged to form a continuous passage between one track and another intersecting or oblique track or another remote parallel track.
CROSSING, TRACK - A structure, used where one track crosses another at grade, and consisting of four connected frogs.
CROSSOVER - Two turnouts with the track between the frogs arranged to form a continuous passage between two nearby and generally parallel tracks.
CROSSOVER, DOUBLE - Two crossovers which intersect between the connected tracks.
CROSSOVER, SCISSORS - Same as Double Crossover.
CURVE, SIMPLE - A continuous change in direction of alignment by means of an arc of a single radius.
CURVE, DEGREE OF (D&R) - The angle subtended at the center of a simple curve by a 10 foot chord.
CURVE, DEGREE OF (AREA only) - The angle subtended at the center of a simple curve by a 100 foot chord.
CURVE, COMPOUND - A continuous change in direction of alignment by means of two or more contiguous simple curves of different degrees having a common tangent at their junction points.
CURVE, EASEMENT - A curve whose degree varies either uniformly or in some definitely determined manner so as to give a gradual transition between a tangent and a simple curve, which it connects, or between two simple curves.
CURVE, REVERSE - Two contiguous simple curves in opposite directions, with a common tangent at their junction point.
CURVE, VERTICAL - An easement curve in the track to connect intersecting grade lines.
DERAIL - A track structure for derailing rolling stock in case of an emergency. (See Switch Point Derail.)
ELEVATION OF CURVES - The vertical distance that the outer rail is above the inner rail.
FASTENINGS - Joint bars, bolts and spikes.
FASTENINGS, AUXILIARY - Spring washers, tie plates, rail braces and anit-creeping devices.
FIELD SIDE (RTT) - 1. The side of a track bordering the right of way line, as opposed to the Six Foot. 2. The side of a rail that faces the outside, as opposed to the Gage Side.
FISHING SPACE (TTC) - The space between the head and base of a rail occupied by the joint bar.
FISH PLATE (TTC) - A short piece lapping a joint, secured to the side of two members, to connect them end to end.
FLANGE HEIGHT (D&R only) - The vertical distance from the top of the flange to the base line of a new wheel tread, or tread portion of a worn wheel, measured at right angle to the center line of the axle.
FLANGEWAY - The open way through a track structure which provides a passageway for wheel flanges.
FLANGEWAY DEPTH - The depth of the wheel flange passageway, or the vertical distance from the top of the tread surface to the top of the filler or separator introduced between the tread portion and the guard portion of a track structure.
FLANGEWAY WIDTH (D&R) - The horizontal distance between the gage surface and the guard surface of a track structure, which provides a passageway for wheel flanges.
FLANGEWAY WIDTH (AREA only) - The distance between the gage line and the guard line of a track structure, which provides a passageway for wheel flanges.
FLARE (D&R) - A tapered widening of the flangeway at the end of the guard surface of a track structure, as at the end of a guard rail or at the end of a frog or crossing wing rail.
FLARE (AREA only) - A tapered widening of the flangeway at the end of the guard line of a track structure, as at the end of a guard rail or at the end of a frog or crossing wing rail.
FROG - A track structure used at the intersection of two running rails to provide support for wheels and passageways for their flanges, thus permitting wheels on either rail to cross the other.
FROG, SELF GUARDED - A frog provided with guides or flanges, above its running surface, which contact the tread rims of wheels for the purpose of safely guiding their flanges past the point of the frog.
FROG NUMBER (D&R) - One-half the cotangent of one-half the frog angle, or the number of units of center line length in which the gage surface spread is one unit.
FROG POINT (D&R) - That part of a frog lying between the gage surfaces extending from the heel and toward the intersection of the gage surfaces.
FROG POINT, ACTUAL NEW (D&R) - The location on the running surface of a new frog point that is farthest from the heel. In order to produce a practical frog point the actual new frog point is not continued to a sharp edge at the theoretical frog point, but instead terminates with a specified blunt edge some distance before the theoretical frog point.
FROG POINT, THEORETICAL (D&R) - The point of intersection of the gage surfaces of a frog.
GAGE, A TOOL - A device by which the gage of a track is established or measured.
GAGE SIDE (RTT) - A reference to the area between the rails of a track, as opposed to the Field Side.
GAGE SURFACE (D&R) - The generally vertical surface along the side of the head of a running rail, or corresponding location of tread portion of other track structures, which is nearer the center of the track. A radius or fillet contiguous to, either above or below, a gage surface shall not be considered part of the surface.
GAGE LINE (AREA only) - A line 5/8 inch below the top of the center line of head of running rail or corresponding location of tread portion of other track structures along that side which is nearer the center of the track.
GAGE OF TRACK (D&R) - The horizontal distance between the gage surfaces, measured at right angle to the center line of track. Measurements shall include any evidence of lateral movement under load.
GAGE OF TRACK (AREA only) - The distance between the gage lines, measured at right angles thereto. (The standard gage is 4 feet 8 1/2 inches.)
GAGING REFERENCE LINE (D&R only) - A vertical line which contacts either a gage surface or guard surface and is perpendicular to a line across the running surfaces. The gaging reference line is used when measuring horizontal distances between gage surfaces and guard surfaces. The horizontal measurement between gaging reference lines shall be taken parallel to a line across the running surfaces and at right angle to the center line of track.
Note: For unguarded track the elevation on the gage surface where the gaging reference line makes contact is of no consequence. For guarded track the distance from a line across the running surfaces to the point at which the gaging reference line makes contact with a gage surface or guard surface must not be less than 50% of the height of a normal wheel flange (0.094 inches) and must not be more than 80% of the height of a normal wheel flange (0.150 inches).
GAGING TOOL, TRACK GAGE (D&R only) - A device having vertical surfaces of specified distances apart that are intended to contact the gage surface of rails, or corresponding location of other track structures, and, when applied, the vertical surfaces are perpendicular to a line across the running surfaces and at right angles to the center line of track. The device is generally used to establish the position of rails in relation to one another before fastening into place.
GAGING TOOL, LIMIT GAGE (D&R only) - A device having vertical surfaces of specified distances apart such that when one vertical surface of the limit gage is brought into contact with either a gage surface or guard surface, an associated vertical surface of the limit gage will either contact or not contact an associated gage surface or guard surface. Instructions for the use of the limit gage specify whether contact or no contact indicates either a satisfactory or unsatisfactory gage condition. This device is generally used to determine if the dimensional relationship between rails and other track structures is correct. The device may also incorporate horizontal surfaces that act in a similar manor.
GUARD SURFACE (D&R) - The generally vertical surface along that side of the flangeway which is nearer the center of the track. A radius or fillet contiguous to, either above or below, a guard surface shall not be considered part of the surface.
GUARD LINE (AREA only) - A line along that side of the flangeway which is nearer the center of the track and at the same elevation as the gage line.
GUARD CHECK GAGE (D&R) - The horizontal distance between guard surface and gage surface, measured across the track at right angle to the center line of track. Measurements shall include any evidence of lateral movement under load.
GUARD CHECK GAGE (AREA only) - The distance between guard line and gage line, measured across the track at right angles to the gage lines.
GUARD FACE GAGE (D&R) - The horizontal distance between guard surfaces, measured across the track at right angle to the center line of track. Measurements shall include any evidence of lateral movement under load.
GUARD FACE GAGE (AREA only) - The distance between guard lines, measured across the track at right angles to gage lines. Measurements shall include any evidence of lateral movement under load.
GUARD FLARE GAGE (D&R only) - The horizontal distance from the guard surface at the wider end of a flare to the gage surface measured across the track at right angle to the center line of track. Measurements shall include any evidence of lateral movement under load.
GUARD RAIL - A rail or other structure laid parallel with the running rails of a track to prevent wheels from being derailed; or to hold wheels in correct alignment to prevent their flanges from striking the points of turnout or crossing frogs or the points of switches.
A rail or other structure laid parallel with the running rails of a track to keep derailed wheels adjacent to running rail.
GUARD RAIL (RTT) - A track work component, frequently made from tee rail and placed next to a running rail. A "working" guard rail guides rolling stock by maintaining contact with the backside of the wheels. A "passive" or "non working" guard rail does not normally contact wheels (See Guardrail, Emergency).
GUARD RAIL, EMERGENCY (D&R only) - A rail located approximately 1 2/3 wheel widths from the running rail (usually between running rails) to keep derailed wheels on the track structure. Emergency guard rails are found on bridges or other locations where derailed equipment could be extremely endangered in a derailment.
GUARD RAIL, EMERGENCY (RTT) - A rail located approximately nine inches from the running rail (usually between running rails) to keep derailed wheels on the track structure. Emergency guard rails are found on bridges or other locations where derailed equipment could be extremely endangered in a derailment.
GUARD RAIL, LEVEL (RTT) - Any working guard rail with its top level with the top of the running rail.
GUARD RAIL, RAISED (RTT) - Any working guard rail with its top higher than the top of the running rail.
GUARD RAIL, WORKING (RTT) - Any rail other than a running rail that contacts the back of wheel flanges to steer wheels sets through a portion of track.
HEEL OF SWITCH - That end of a switch rail which is farther from its point, and nearer the frog.
HEEL SPREAD (D&R) - The distance, at the heel, between the gage surface of a switch rail and the gage surface of its stock rail. Measurements shall include any evidence of lateral movement under load.
INSULATION - A device or material that prevents the flow of electric current in a track circuit from one rail to another or through switches and other track structures.
JOINT BAR - A steel member, embodying beam strength and stiffness in its structural shape and material; commonly used in pairs for the purpose of joining rail ends together, and holding them accurately, evenly and firmly in position with reference to surface and gage side alignment.
JOINT DRILLING - Same as Splice Drilling.
JOINT, RAIL - A fastening designed to unite the abutting ends of contiguous rails. (Also see Joint Bar.)
JOINT, INSULATED - A rail joint designed to arrest the flow of electric current from rail to rail by means of insulations so placed as to separate the rail ends and other metal parts connecting them.
LEVEL - The condition of track in which the elevation of the two rails transversely is the same.
LINE - The condition of the track in regard to uniformity in direction over short distances on tangents, or uniformity in variation in direction over short distances on curves.
LINING TRACK - Shifting the track laterally to conform to the established alignment.
MAIN LINE - The principle line or lines of a railway.
OUT OF FACE - Work that proceeds completely and continuously over a given piece of track, as distinguished from work at disconnected points only.
POINT OF SWITCH, ACTUAL (D&R) - That end of a switch rail which is farther from the frog.
POINT OF SWITCH, THEORETICAL or VERTEX (D&R) - The point where the gage surface of the switch rail, if produced, would intersect the gage surface of the stock rail.
RAIL (D&R) - A metal bar shape designed to be laid end to end in two parallel lines on cross-ties, or other suitable supports, to form a track for railway rolling stock.
RAIL (AREA only) - A steel bar (usually a rolled shape) designed to be laid end to end in two parallel lines on cross-ties, or other suitable supports, to form a track for railway rolling stock.
RAIL, RUNNING (D&R only) - A rail on which the treads of wheels bear.
RIGHT ANGLE TO THE CENTER LINE OF TRACK (D&R only) - For tangent track the description is exactly correct. For curved track the description shall be taken to mean parallel to a radius line.
SIX FOOT (RTT) - A term describing the space between two tracks, i.e. the space between the ends of ties of double track.
SLIP CROSSING, SINGLE (PRR) - A combination of a crossing with one right hand and one left hand switch and curve between them within the limits of the crossing and connecting the two intersecting tracks without the use of separate turnout frogs.
SLIP CROSSING, DOUBLE (PRR) - A combination of a crossing with two right hand and two left hand switches and the curved rails between them within the limits of the crossing, and connecting the two intersecting tracks on both sides of the crossing without the use of separate turnout frogs.
SPECIAL TRACKWORK - All rails, track structures and fittings, other than plain unguarded track that is neither curved nor fabricated before laying.
SPIRAL - A form of easement curve in which the change of degree of curve is uniform throughout its length.
SPLICE BAR - Same as Joint Bar.
SPLICE DRILLING - The spacing of holes in the ends of rails or other track structures to receive the bolts for the fastening of joint bars.
SPUR - A line of railway, diverging from a main or branch line, over which no regular train service is maintained.
STOCK RAIL - The running rail against which the switch rail operates.
STOCK RAIL BEND (D&R) - The bend or set which must be given the stock rail at the vertex of a switch to allow it to follow the gage surface of the turnout.
SURFACE, TRACK - The condition of the track as to vertical evenness or smoothness.
SURFACE, RUNNING or TREAD - The top part of track structures on which the treads of wheels bear.
SWITCH - A track structure used to divert rolling stock from one track to another.
SWITCH, SPLIT - A switch consisting essentially of two movable point rails with the necessary fixtures.
SWITCH, SPRING - A switch in the operating mechanism of which is incorporated a spring device so arranged as to automatically return the points to their original or normal position after they have been thrown over by the flanges of trailing wheels passing along the other track from that for which the points are set for facing movements.
SWITCH POINT, SWITCH RAIL or POINT RAIL (D&R) - The tapered movable rail of a split switch.
SWITCH POINT DERAIL - A derail consisting essentially of a split switch point with the necessary fixtures.
SWITCH POINT SPREAD (D&R only) - The horizontal distance from the surface on the opposite side of the gage surface at the toe of an open switch point to the gage surface at the toe of the closed switch point measured at right angle to the center line of track.
Note: The switch point spread shall conform to the dimensions and tolerances specified for the guard flare gage.
SWITCH THROW (D&R) - The distance through which the points of switch rails are moved sidewise, measured along the center line of the No. 1 switch rod or head rod.
SWITCH STAND - A device for the manual operation of switches, or of movable center points.
SWITCH STAND, SEMI AUTOMATIC (RTT) - A switch stand with an internal mechanism that allows rolling stock making trailing movements through a switch set in the improper position. The switch stand mechanism completes the throw of the switch.
SWITCH STAND THROW (D&R only) - The sidewise distance that the switch stand imparts to the switch rod or switch mechanism to which it is connected. The switch stand throw may be greater than the switch throw in order to properly operate a switch mechanism interposed between the switch stand and the point rails of a switch.
TANGENT - Any straight portion of a railway alignment.
TAPER RAIL - Same as Compromise Rail.
TIE, CROSS (TTC) - The transverse member of the track structure to which the rails are spiked or otherwise fastened to provide proper gage and to cushion, distribute, and transmit the stresses of traffic through the ballast to the roadbed.
TIE, SWITCH (TTC) - The transverse member of the track structure which is longer than, but functions as does the cross tie and in addition supports a crossover or turnout.
TIE PLATE - A plate interposed between a rail or other track structure and a tie.
TRACK - Ties, rails and fastenings with all parts in their proper relative positions.
TRACK BOLT (D&R) - A bolt and a threaded nut designed to fasten together rails and joint bars and other joint fastenings.
TURNOUT - An arrangement of a switch and a frog with closure rails, by means of which rolling stock may be diverted from one track to another.
TURNOUT, EQUILATERAL (TTC) - A turnout in which the diversion due to the angle of the turnout is divided equally between the two tracks.
TURNOUT, LATERAL (TTC) - A turnout in which the diversion due to the angle of the turnout is entirely on one side of the track from which the turnout is made.
TURNOUT NUMBER (TTC) - The number corresponding to the frog number of the frog used in the turnout.
WYE - A track with two connecting tracks, arranged like the letter "Y," by means of which rolling stock may be turned.