To Create Roundabouts

In order to define a roundabout you will first need to identify the alignments of the arms (the incoming roads). If they don't already exist, draw accurate centrelines of each arm extending to at least to the point where the new roundabout will join any existing road (blend point).

1. Click Home tabCreate Design panelJunctions drop-downCreate Roundabout.

2. In the New Roundabout Details dialogue box, select the desired options.

   • You can enter a Name for the roundabout as well as Notes and/or a Description.
   • Select Calculate Elevations to place the roundabout using existing elevations.
   • The Inscribed Circle Diameter is the diameter of the definition line that represents the outer limit of the roundabout. Note that if a kerb offset has been defined then the actual kerb will not coincide with the definition line.
   • The centre island diameter is the diameter of the island around which the vehicles turn. It does NOT include the apron or overrun area.
   • The Apron Diameter is the diameter of the overrun area.
     Note: The apron is regarded as falling outside the central island.
   • Select the number of Circulatory Lanes for the roundabout.
   • You can also choose a Draw Style from the drop down list. This controls how the roundabout displays.
   • For the Existing Surface, select from the drop-down list or use the Pick button to go to a drawing and select an object on the surface.
   • Final Surface is the surface onto which objects can be projected. Select from the drop-down list or use the Pick button to go to a drawing and select an object on the surface.
   • You can select Project Plan Onto Final Surface to display the roundabout draped over the surface.
3. Click OK.
4. Select the centre of the new roundabout.
5. Select the new access road centreline.
6. In the New Leg dialogue box, select the desired options and click OK.
7. Select the new access road centreline.
8. In the New Leg dialogue box, select the desired options and click OK.
9. Select the new access road centreline.
10. Continue selecting access roads, then press Enter when finished.

The roundabout is created in the drawing.