Regarding width of rr cars & track

[DaveDunlop]

One perspective is to look at the theoretical. The other is to look at
a practical and evolutionary way to get started on a lunar rr. If the
Constelllation program is continued by the next administration
(questionable
at this point) then we can take the 33 diameter of the fairing of the
Ares V as a figure of merit for discussion. For discussion purposes
lets just use
30 feet in diameter as a maximum for the width of a habitation module.
This fairing I believe is also some 60 ft in length. Presumably the
AVES V architecture can get something this large on the lunar surface.
Once there
a unit this size would need to be moved around and away from the
landing
site. I would be more stable if a cylinder of this size could be
moved with
it's long axis to the lunar surface. Some support system with rugged
wheels or tracks will be needed to manuever units like this around the
surface.

If we simply take the amount of logistics activities connected with
setting
up and maintaining a supply chain for the lunar base there will be an
excellent rationale to get a small dedicated rail system in place
ASAP.
It may sound far fetched by the standards of typical US dimensioned
rail cars but with life support requirements the scale and volume
necessary
make a "large car" type of vehicle .

I think for this reason that instead of a specia car we are much mor
likely see a standard habitation unit also use as a mobile unit.