Right of Way needed for an interchange?

[kernals12]

For a diamond or spui interchange, how much space do you need outside of the mainlines of the arterial?

And if using left handed ramps, how much space do you need in the median?

[Dirt Roads]

For a diamond or spui interchange, how much space do you need outside of the mainlines of the arterial?

Here in North Carolina, the typical right-of-way is either 50 feet from centerline of closest lane (rural) or 30 feet (urban).  But keep in mind this is a three-dimensional problem.  The actual ROW can get extended due to cuts, slopes and drainage requirements.  North Carolina typically requires all roadway projects to include an additional 5 to 10 feet beyond the construction limits.  But some states will try to get adjacent property owner(s) to allow temporary construction easements onto those properties to extend the slopes (oftentimes, a desired aesthetic improvement). 

If you are so inclined, try to take a typical vertical profile and modify it to a particular situation to get a feel for how far the construction might extend from the centerline of the closest lane.  Use a typical slope of 1:1, but in some cases you might need to increase the slope to 2:1 (rise over run) to minimize the right-of-way.  (North Carolina requires that benches be constructed if the existing slope exceeds 4:1, but that is getting out of my capabilities).