Two sets of tracks encircle the Moon on the Equator. Both carry immense trains - Caravans - with cars the size of football fields, that use multi-storey concourses running from front to back the length of the train along the sides, for inter-module commuting.
The SOLAR SIDEREAL line...
of two Caravans that run at ~12mph: one always directly under, the other opposite, the Sun (both occasionally compromised in functions by the nearby, big-ass planet)
The Sunside Caravan is all about power, light and heat: charging batteries (both electrical and thermal), running continuous ore smelting, and high energy fabrication and research. The wings of the full-length parabolic trough that does all the work splay far off to the sides.
The Darkside Caravan is all about energy dissipation: it produces liquid gases, the cold side of thermal batteries, and cryo-research. It features dual troughs, which are angled further outwards when the Earth is overhead... which is the busy time for the clear-domed skating rink.
The EARTH SIDEREAL line...
...hosts Caravans synchronized with Earth time-zones, running at a bit over 200mph to accomplish same (once around the Moon in one day). Their function is to make transplanted Terran flora and fauna feel right at home.
The sun comes up in the morning and sets in the evening of each 24 hour day which suits all the plants, animals and people just fine. For convenience and variety, the produce from the land-and-sea farms and ranches of each train matches that of their equivalent timezone on Earth.
It's living quarters and offices for all the government and business representatives whose working day is tied to that of their home offices on Earth.
Just as importantly, the hosted hotel modules are also timezone slices of the Earth: culture, language, cuisine ; local, synchronized time ensures that visitors to the Moon don't even have to deal with jetlag.
Each Caravan's multifunction "locomotive" and "caboose" cars, 200x the size of their earthbound brethren, are modelled after great historical train cars.
[I've reworded this post numerous times; the original from early 2008 also contained the idea of tangential landing/takeoff using a continuous equatorial runway. That idea now resides as a massive footnote in "Orbital Hovercraft", where it's more relevant]