As an FYI, I did a quick search on interstate width requirements and
found the following document...
http://en.wikipedia.org/wiki/Interst...hway_standards
So a two-lane interstate like I-80 in rural areas would be:
12 ft (lane #1)
12 ft (lane #2)
10 ft (shoulder #1)
4 ft (shoulder #2)
--------------------------------
38ft
So it would be possible to put a light single down on in the center
and not even hit a mile marker or reflector post on the sides...

And if you fly a high wing airplane, you don't even need that much
width! ;_)