RailDoubleTrackCANT

The RailDoubleTrackCANT subassembly is used to insert the rails, ties, ballast, subballast, soil fill, and subbase for a double-track railroad.

It should be followed with a Daylight subassembly on the left and right sides to close to existing ground in cut and fill situations. It is capable of responding to rail cant.

Attachment

By default, the attachment point is at the centerline between the rails of the left track. The tracks can be moved relative to this point using the subassembly parameters.

Input Parameters

Note: All dimensions are in meters or feet unless otherwise noted. All slopes are in run-over-rise form (for example, 4 : 1) unless indicated as a percent slope with a “%” sign.

Parameter	Description	Type	Default
Measure Cant At	Determines whether the elevation difference between rails takes place between the gauge line (face) of each rail or CL of each rail.	Selection List: Gauge Line to Gauge Line CL Rail to CL Rail	CL Rail to CL Rail
Default Cant	The default elevation difference between rails. The value is positive when the right rail is higher than the left and negative when the right rail is lower than the left. This value is applied in layout mode and is helpful for observing how the subassembly reacts to different cant values. This value is overridden by cant when it is present via the baseline alignment.	Numeric	0
Drainage Channel Depth	Depth of drainage channel from top of ballast.	Numeric, non-negative	0.5 ft 0.1524 m
Gauge	The distance between the inside faces of the rails	Numeric, non-negative	56.5" 1435 mm
Baseline to Right Track CL	The offset from the baseline alignment to the centerline of the left or right track.	Numeric	0
Baseline to Left Track CL	The offset from the baseline alignment to the centerline of the left or right track.	Numeric	20' 6m
Track Elevation Difference (Left and Right)	The vertical offset between the profile grading point of the baseline and the center point between the tracks. This value is overridden when an elevation target is applied to the track.	Numeric	0
Rail Head Width	Width of the rail head.	Numeric, non-negative	2. 72" 69 mm
Rail Depth	Depth of rail from top of rail to top of tie plate	Numeric, non-negative	6.625" 168 mm
Rail Base Width	Width of the base of the rail	Numeric, non-negative	5.5" 0.14 m
Tie Plate Thickness	Thickness of the tie plate which is also the distance from the bottom of the rail to the top of the tie.	Numeric, non-negative	1" 25 mm
Rail Base to Ballast	Distance from the bottom of the rail to the top of the ballast. If this value is equal to the tie plate thickness, then the top of the ballast is flush with the tops of the ties.	Numeric, non-negative	1" 25 mm
Tie Length	Length of the tie (also known as sleeper).	Numeric, non-negative	8.5' 2.59 m
Tie Depth	Depth of tie	Numeric, non-negative	7" 178 mm
Minimum Ballast Depth	The minimum vertical distance between the bottom of the tie and the top of the Subballast. The location of this minimum distance changes at different stages in cant. See "Behavior" below.	Numeric, non-negative	12" 305 mm
Ballast Shoulder Width (Left and Right)	The distance from the end of the tie to the beginning of the ballast side slope.	Numeric, non-negative	1 ft 0.30 m
Ballast Side Slope (Left and Right)	The slope of the side of the ballast material. The slope of the top of the ballast material matches the slope of the tie that results from cant.	Slope, non-negative	2:1
Subballast Depth	The depth of the subballast material	Numeric, non-negative	8" 203 mm
Baseline to Subballast Crown	The offset from the baseline to the crown of the subballast.	Numeric	10' 3 m
Subballast Top Slope	The top slope of the left and right sides of the subballast with the centerline of the subassembly as the hinge point.	Slope, non-negative	40:1
Subballast Extension (Left and Right)	The distance from the toe of the ballast material to the beginning of the side slope of the subballast material	Numeric, non-negative	12" 0.30 m
Subballast Slope	The slope of the side of the subballast material.	Slope, non-negative	2:1
Omit Rails	Prevents the rail points, links, and shapes from being drawn.	Yes/No	No
Omit Ties	Prevents the tie points, links, and shapes from being drawn.	Yes/No	No
Omit Ballast	Prevents the ballast points, links, and shapes from being drawn. If this option is set to Yes then the subballast is also not drawn.	Yes/No	No
Omit Subballast	Prevents the subballast points, links, and shapes from being drawn. If the Omit Ballast option is set to Yes then the subballast is not drawn regardless of this setting.	Yes/No	No
Omit Soil Fill	Prevents the soil fill points, links, and shapes from being drawn. If the Omit Ballast or Omit Subballast option is set to Yes then the soil fill is not drawn regardless of this setting.	Yes/No	No
Sub_Base Slope	The slope of the side of the SubBase material.	Slope, non-negative	1:1
Sub_Base Extension	The distance from the toe of the subballast material to the beginning of the side slope of the SubBase material	Numeric, non-negative	0.5' 150 mm
Sub_Base Depth	The depth of the SubBase material	Numeric, non-negative	12" 300 mm
Omit SubBase	Prevents the SubBase points, links, and shapes from being drawn. If the Omit Ballast, Omit Subballast, or Omit Soil Fill option is set to Yes then the SubBase is not drawn regardless of this setting.	Yes/No	No
Soil Fill Slope	The slope of the side of the Soil Fill material.	Slope, non-negative	1:1
Soil Fill Depth	The depth of the Soil Fill material	Numeric, non-negative	12" 300 mm
Soil Fill Extension	The distance from the toe of the soil fill material to the beginning of the side slope of the Subballast material.	Numeric, non-negative	0.5' 150 mm

Target Parameters

This section lists the parameters in this subassembly that can be mapped to one or more target objects. For more information, see To Specify Corridor Targets.

Parameter	Description	Status
Left Track Offset	May be used to set the horizontal location of the centerline of the left track.	Optional
Right Track Offset	May be used to set the horizontal location of the centerline of the right track.	Optional
Left Track Elevation	May be used to set the elevation of the center point between the left rails. Cant is applied after this point is located so the actual point between rails may vary since rotation can occur around either of the rails.	Optional
Right Track Elevation	May be used to set the elevation of the center point between the right rails. Cant is applied after this point is located so the actual point between rails may vary since rotation can occur around either of the rails.	Optional

Runtime Logical Assignments

None.

Output Parameters

None.

Behavior

When no targets are applied, the location of either track is determined by the Left Track Offset, Right Track Offset, Left Track Elevation Difference, and Right Track Elevation Difference. These values locate the center points between the tracks. By default, the Left Track Offset is zero placing the centerline of the left track at the baseline. When target alignments and profiles are applied, these values are overridden. When using target alignments for the track centerlines, the tracks always remain perpendicular to the baseline, not the target alignment. When the target alignments are not parallel to the baseline alignment, distortion will occur and the track dimensions will not be accurately represented.

Important: The RailDoubleTrackCANT subassembly calculates cant from the single center alignment and not from targets. True offset tracks may have different curve geometry and design speeds that the centerline calculation cannot accommodate. This subassembly is for primary design. For accurate cant calculation, separate baselines modeling the Left and Right Multi Track subassemblies should be used.

When you apply rail cant information to the alignment baseline, the rails rotate accordingly. The point about which they rotate depends on the Pivot Method setting contained in the cant information for the alignment. If you set a Pivot Method to Low Side Rail, then the rail on the inside of the curve is held at track elevation and the elevation of the outside rail is adjusted an amount equal to the cant value.

If you set the Pivot Method to High Side Rail, then the rail on the outside of the curve is held at track elevation and the elevation of the inside rail is adjusted an amount equal to the cant value.

If you set the Pivot Method to Center Baseline, then both rails are adjusted an amount equal to half the cant value, the outside rail upward and inside rail downward.

The Minimum Ballast Depth value applies at the location of the minimum clearance between the tie and subballast. The Subballast Top Slope parameter independently controls the subballast top slope . The Baseline to Subballast Crown parameter controls the location of the subballast crown.

Layout Mode Operation

In layout mode the subassembly displays the links comprising the rails, tie, ballast, subballast, and side slopes.

Point, Link, and Shape Codes

The following table lists the point, link, and shape codes for this subassembly that have codes assigned to them. Point, link, or shape codes for this subassembly that do not have codes assigned are not included in this table.

Point, Link, or Shape	Code	Description
L32	Ballast,Ballast_Between_Ties	Ballast material in open space between ties. Can also be used when ties are omitted.
L116-L119	Top, SoilFill	SoilFill
L120-L121	SoilFill, SubBase"	SoilFill
L122-L125	Top, SubBase	SubBase
L126-L127	SubBase, Datum	SubBase
S1, S2	Rail	Rails
S3	Tie	Tie
S4	Ballast	Ballast
S5	Subballast	Subballast
S6	SubBase	SubBase
S7	SoilFill	SoilFill

Coding Diagrams