There are a lot of civil softwares which have a particular type of alignment entity called "circle", especially for Roundabouts.
Here, even in the "Create Roundabout" of Vehicle Tracking, it needs 2 arcs to define a circle as the alignment of the roundabout.
Please, add another Alignment Entity called "circle" within the Fixed arc category in the "Geometry Editor Tool".
And use directly this type of entity in the Autodesk Vehicle Tracking.
Moreover, we can´t create an alignment from object (an ACAD Circle object).