To add a target for an arm in a roundabout corridor

Issue:

You want to know how to add a widening to a roundabout corridor arm in Civil 3D.

Causes:

There is only the possibility to target to one side and this targets to the road centerline alignment.

Solution:

An arm in a roundabout corridor uses the curb alignment and targets to the centerline alignment. 
As the subassembly is only on the right or the left, it can only target to one side.

Workaround:

• Add a very small / short additional subassembly of the same type
• Target this subassembly to the feature line