Roundabout Properties: Arm: Levels & Grades

Expand an arm and click Levels in the left-hand pane. The Levels Grades page is displayed.

By default, Autodesk Civil 3D 2025 takes the arm elevation and longitudinal gradient at the Deviation Point from the existing surface. To specify a different level or gradient, select User Defined Elevation and Grade from Take Elevation and Grade From drop-down list and enter the required values in Elevation and Grade. Grade is measured towards the roundabout and a positive gradient is increasing level.

The Vertical Transition Arc is a user defined arc of given radius where one end of which is tangential to the incoming road.

Crownlines

Note: Crownlines must be selected in the Roundel tab for these fields to be editable.

The Entry Side Transition Mode controls which method is used to define the entry crownlines.

• Custom
• Place Transition at Blend Point
• Place Transition at Deviation Point
• Place Transition at Splitter Deviation point

The Entry Side Cross Slope calculates the entry crossfall from the crownline of the road to the curb and is used to calculate the elevation of the outside curb, between the blend point and the change in transition.

The Entry Side Transition Distance sets the location for the entry transition.

Note: This field is only available when Custom is selected for the Entry Side Transition Mode.

The Deviation Offset From ICD sets the offset of the crossfall from the ICD location.

The Crown Line Offset at Entry sets an offset for the entry crown line as a percentage.

The Exit Side Transition Point controls which method is used to define the exit crownlines.

• Custom
• Place Transition at Blend Point
• Place Transition at Deviation Point
• Place Transition at Splitter Deviation point

The Exit Side Cross Slope calculates the exit crossfall from the crownline of the road to the curb and is used to calculate the elevation of the outside curb, between the blend point and the change in transition.

The Exit Side Transition Distance sets the location for the exit transition.

Note: This field is only available when Custom is selected for the Exit Side Transition Mode.

The Deviation Offset From ICD sets the offset of the crossfall from the ICD location.

Crown Line Offset at Exit sets an offset for the exit crown line as a percentage.

In all cases the Max and Min values represent the limiting values from the adopted design standard.