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 centerlines of each arm extending to at least to the point where the new roundabout will join any existing road (the blend point).

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

2. On the New Roundabout Details dialog 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 have the roundabout be placed using existing elevations.
   • The Inscribed Circle Diameter is the diameter of the definition line that represents the outer limit of the outer curb of the roundabout. Note that if a curb offset has been defined then the actual curb will coincide with the definition line.
   • The Center 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 how many 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 center of the new roundabout.
5. Select the new access road center line.
6. On the New Arm dialog box, select the desired options and click OK.
7. Select the new access road center line.
8. On the New Arm dialog box, select the desired options and click OK.
9. Select the new access road center line.
10. Continue selecting access roads then press Enter when finished.

The roundabout is created in the drawing.