The shape of prime base

[mmartin798]

Originally Posted by tsofian

That would be a huge tunnel. Plus 26 feet wide would be plenty wide enough for moving tractor trailers and loads

I am not so sure. While I haven't found any reports or guidelines for turning radius of a 20' trailer and have not worked the formulas, there are plenty for 45' trailers. For a semi to do a 180deg turnaround requires a straight road about 91' wide. If this were a tunnel, the 91' would be where the front outside corner of the truck was just brushing against the wall. If this scales close to linear, then you still need about 40' wide straight tunnel, more if it is a circular tunnel. It is possible to use specialized mules that are close in size to the hitch to minimize the turning and turn the prime movers with no trailer. This will reduce the efficiency but may do the job. But if you just want to hook up the trailer and go, a double wide tunnel is in order.