Roundabout and traffic circles are a common form of intersection control used throughout the world and are becoming more and more popular in the United Stated. Civil 3D 2010 was the first to introduce the roundabout feature as a subscription download. The new Civil 3D 2011 has added the roundabout feature to the Home contextual tab under the create design ribbon. The new roundabout feature allows you to create and edit a 2D roundabouts design. The 2D roundabout feature commands can produce roundabout central areas, approach roads, slip lanes, and pavement marking and signage. When you create a roundabout, it automatically created a group of new alignments and polylines that represent roundabout components. Two important items to look for when designing your roundabout is approach lane curb return overlaps and editing the roundabouts. Roundabouts created using the Create Roundabout command can only be edited in versions of AutoCAD Civil 3D that contain the roundabout creation functionality. I have provided images and A short video presentation on how to create a basic roundabout.
Corridoring a roundabout can be a little confusing and tricky. I just recently designed and corridored two roundabouts in a subdivision I was working on. To save time, I corridored the roundabout with a few profiles and feature lines. You can use the intersection feature but you could be looking at very complex corridor and subassemblies. In part 2 of my post on roundabout, I will show you how a few shortcuts on corridoring a roundabout. Please feel free to make comments or email me if you have question.