Someday, humanity may build cities in space. If and when that day comes, NASA says they should be exactly what urbanists advocate for here on Earth: walkable, transit-oriented, dense, and inclusive.
In 1977 NASA published Space Settlements: A Design Study, a 155-page book that amounts to a city planning policy guide on what future space colonies should look like.
The guide isn't about research space stations like the ISS, nor is it about colonies on the surface of other planets or moons. Rather, it focuses on orbital civilian habitats—town-sized space stations that could house tens of thousands of civilians each.
Such “habs” have been a staple of science fiction for decades, but they do actually follow the real-world laws of phsyics. Cost and will notwithstanding, they're physically possible to build. If space ever becomes widely accessible or more heavily settled, these types of orbital towns could become reality.
NASA's city planning guidelines
Space Settlements is a broad guidebook covering everything from how much air a colony would need, to what kinds of rockets might service it, to the likely sociology of the people inside. It includes, admittedly, a lot of guesswork.
It also includes a fascinating chapter on town planning that looks remakably like a basic comprehensive plan. There are sections on how much space will be needed for residences, retail, schools, and other land uses, plus transportation and other infrastructure.
Regarding transportation, the guide has this to say:
Because of the relatively high population density (15,000 people/km2) in the community, most of the circulation is pedestrian, with one major mass transport system (a moving sidewalk, monorail, and minibus) connecting different residential areas in the same colony.
There's even a diagram, illustrating the space requirements of various types of streets.
That's a transit pod on the arterial. There will be no private cars on space stations.
Parks must be tall enough
At first, the paragraph devoted to parks looks much like the guidelines for most other land uses, focusing on calculating the area to be devoted to that land use per habitat resident.
Averaged over 53 U.S. cities the open space for parks and such is 18 m2/person. DeChiara and Koppelman recommend 14 m2/person. Because the space habitat contains agricultural areas that can be in part used as open space, a lower value of open space in the residential area is adopted, namely 10 m2/person.
But then we get a curveball: In an enclosed habitat where residents literally cannot go outside, where there's no escape from the claustrophobic walls around them, the height of parks matters as much as their area.
To allow a true feeling of being “open” the space has to be tall enough. This height is taken to be 50 m.
Humanity's diverse future
As for demographics, NASA pulls no punches that humanity's future is not going to be a Leave It To Beaver episode:
The first extraterrestrial communities may not be purely American if the United States is no longer a major world power or a major technological center by the time the first extraterrestrial community is established. If the United States remains a major world power, many nations including nonwestern nations and African nations could be highly technological and want to participate, so that the first extraterrestrial community may be international.
The present technological nations are not necessarily advantaged, because the technology they possess is “Earth-bound” in addition to being culture-bound. They may have first to unlearn the forms, the assumptions and the habits of the Earth-bound technology before learning the new forms and assumptions of technology useful in extraterrestrial communities.
I stumbled on Space Settlements while visiting NASA's awesome Headquarters Library, which is in the Southwest DC Federal Center and is open to the public. You can peruse a pdf copy of the book online, but I highly recommend checking out the library itself for its impressive collection.
And if planning mere cities is too small scale for you, try this one: