AutoCAD Civil 3D 2017 Roundabouts can be modeled according to defined standards.
Terminology varies around the world but in UK terms, roundabouts can be modeled as normal and compact.
AutoCAD Civil 3D 2017 creates roundabouts that blend with existing or planned roads. The point on each incoming road, or arm, at which the roundabout model starts is called the blend point. So, if you have four roads leading into your roundabout you will have four blend points.
Once placed, every aspect of your roundabout model, including the location of the blend points, can edited using either grips or using the properties dialog.
The default geometry of your roundabout is determined by the standard that you select. The standards that we supply are locked to prevent accidental (or intentional) changes but you can create your own and these can be password protected.
The standard defines limits for each geometric value. Values may also be unlimited. As you adjust your roundabout model, AutoCAD Civil 3D 2017 checks the geometry against these limits and displays an immediate warning if a value goes outside the specified range. These warnings are also used by the Design Check tool and here you are able to enter a justification for the transgression.
The appearance of the roundabout, line colors, styles, thicknesses, etc. is controlled by styles. A single style comprises the attributes of all the elements of the roundabout model such as curbs, pedestrian crossings and so on.