Design Criteria

Set design criteria.

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Command

Shortcut Key

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RD_DESIGNCRITERIA

 

 

This function allows you to specify design criteria for the Horizontal alignment, Vertical alignment and Superelevation design. You can either use the default TRH 17 values, or create and use your own design criteria file.

Check the Use Design Criteria option to use the design criteria in the design process and specify the Design Speed for the road.

Designing roads that do not meet the design criteria specification does not stop you from using them as such. The design criteria serve only as a warning to the user.

Procedure

The Design Criteria displays.

Horizontal Alignment

  1. Enter the Horizontal Alignment design criteria into the Horizontal spreadsheet.
  1. When any of these values are exceeded during the horizontal alignment design, warnings display on the Design Centre window at the relative alignment item in the grade pen. These warnings also appear when running Review Alignment.

Vertical Alignment

  1. Enter the Vertical Alignment design criteria into the Vertical spreadsheet.
  1. When designing the vertical alignment using the Graphical View, the grade criteria displays as a set of grade envelopes at each VPI. Furthermore, when using Review Alignment or Abridged Review, curves that do not pass the selected design criteria you are notified as to the reasons for that failure. Inserting a VPI automatically calculates a curve length, based on the specified K value for the type of curve.

Superelevation

  1. Enter the Superelevation design criteria into the Super spreadsheet.

  1. The Superelevation design criteria is applied when using the Slave Super function. The calculated values can be overwritten at any time while running Slave Super.

See the Superelevation Design topic for a detailed explanation of the superelevation design process.

TRH 17 Lane Factors for Superelevation Run-Off

Cross Section

 

Nr. of Lanes

Lane Factor

Median Width

Undivided

2

1.0

-

Undivided

3

1.2

-

Undivided

4

1.5

-

Undivided

2

1.5

Less than 4.6 m

Undivided

3

2.0

Less than 4.6 m

Divided

2

1.0 or 1.5

4.6 to 12.2 m

Divided

3

1.2 or 2.0

4.6 to 12.2 m

Divided

2

1.0

Greater than 12.2 m

Divided

3

1.2

Greater than 12.2 m

Superelevation Rates Graph

  1. Enter the radii at each design speed next to the appropriate super elevation rate,e in percentage. When changing any of the values, the graph is updated instantaneously.

  2. Click OK to accept and save the changes.