Required Definition Files: standard

The median ditch slope criteria incorporates a set of standard and user defined variables by which the location of the median ditch point and the resulting slope values are controlled and/or set by the designer. The point(s) at which the subgrade earthwork lines tie to the finished grade ditch slopes are also controllable by the designer via a user defined variable.

"MDS01 METHOD"
Specifies the desired method of locating the median ditch point.
Valid definitions are 0, 1 or 2.

0	When defined as zero, the ditch point will be centered between the edges of the two shape clusters without regard to shoulder widths.
1	When defined as one, the ditch point will center under most normal situations, but will "float" left or right if necessary to maintain a maximum slope of 4:1.
2	When defined as two, the ditch point is located at the elevation of the median ditch grade profile. The horizontal location may "float" left or right of center if necessary to maintain the maximum slope.

Default definition = 0.

"MDS01 DITCH GRADE"
Defined as the name of the GEOPAK profile grade to be used in locating the ditch point. This variable is referenced by the criteria only when "MDS01 METHOD" = 2, otherwise definition is not necessary.

"MDS01 DITCH SLOPE"
By default, the median ditch criteria sets the normal ditch slope value according to the width of the median, (as measured from edge of shape cluster to edge of shape cluster). The designer has the option of over-riding this by defining "MDS01 DITCH SLOPE" as the desired normal ditch slope value. If normal slope over ride is not desired this variable should not be defined by the designer, as it is default defined to zero by the standard.met definition file.

"MDS01 SUBGRADE TIE"
Defines the vertical distance above the ditch point at which the subgrade earthwork lines are to tie into the ditch slope.
Default definition = 0.

"MDS01 MAX DITCH SLOPE"
"MDS01 MAINTAIN MAX SLOPE"
The MAX DITCH SLOPE variable controls the manner in which the criteria determines the median ditch point. When the MAINTAIN MAX SLOPE is defined as non-zero, the criteria will attempt to set the median ditch without using a slope value steeper than MAX DITCH SLOPE.
Default definitions: MAX DITCH SLOPE = 4, MAINTAIN MAX SLOPE = 1

"MDS01 MEDIAN GUARDRAIL LINE" New!
When defined as non-zero, this variable causes the criteria to check for presence of guardrail elements in a plan view graphics design file. If found, it's horizontal location is used to place guardrail cells. Guardrail shoulder widening is not performed in median shoulders. Guardrail cells can be placed and located on the shoulders or on the median ditch slopes.
The default definition, taken from the global variable MEDIAN GUARDRAIL LINE, is 0.
*** NOTE: Guardrail cells are located in the Roadway workspace. ***

Example:

DEFINE "MDS01 MEDIAN GUARDRAIL LINE" 1

"GUARDRAIL LINE" New!
This variable is defined via a DEFINE_DGN statement, and specifies the symbology of guardrail elements in the a plan view graphic design file. Guardrail lines can be drawn on the shoulders and median ditch slope in a plan view. Note that the same DEFINE_DGN "GUARDRAIL LINE" line statement can used in conjunction with WIDEN BY GUARDRAIL LINE and/or MEDIAN GUARDRAIL LINE. Shoulder widening is not performed on median shoulders.
GUARDRAIL LINE is a global type variable. There are no corresponding local versions.

Example:

DEFINE_DGN "GUARDRAIL LINE"\
      DGN = R2006_RDY_DSN_XSDGNELEMENT.DGN\
     TYPE = LINE,LINE_STRING,ARC,CURVE\
     LVNAME = PROP DGN ELEMENT GUARDRAIL

To draw median ditch slopes correctly, there are two problems to overcome.

1. At the point of inclusion on the left side of the median, the right median shoulder has not yet been established or drawn. Therefore, since the configuration of the median slopes is determined by the relationship of the two shoulders, the necessary data for setting the median slopes is not yet available to the median ditch slope criteria.
2. When included on the right side of the median; the shoulder points on the left side cannot be referenced by the standard shoulder marked point numbers. That's because those points were re-marked by shoulder criteria for the right side median shoulder.

The solution to both problems is simple. When included on the left side of the median, the criteria does not actually do any drawing. It's only function on the left side is to mark points 81, 80, 83 and 86 on the left side shoulder points 21, 20, 28 and 27 respectively. Then when shoulder criteria re-uses the shoulder marked point numbers for the right side median shoulder, points 80, 81, 83 and 88 remain on the left shoulder to be compared to the right side median shoulder.

"MDS01 METHOD" = 1
A tentative ditch point is set by 'tracing' from the low-side shoulder point to the horizontal center of the median. The slope from that tentative ditch point to the high side shoulder point is computed. If the resulting slope is steeper than 4:1, the ditch point is reset by 'tracing' from the high-side shoulder using a 4:1 slope value to intersect the tentative 'standard' slope. This method will sometimes cause the horizontal location of the ditch point to "float" left or right of center.

"MDS01 METHOD" = 2
A tentative ditch point is set by 'tracing' from the low-side shoulder point using the 'standard' slope value to the elevation of the median ditch grade profile. This point is marked as 84. Then another tentative ditch point is set by 'tracing' from the high-side shoulder point using a 4:1 slope to the elevation of the median ditch grade profile. This point is marked as 85.
The horizontal relation of points 84 and 85 are then compared and the final ditch point, 82, is marked as follows: