|A basic city with only surface streets|
This is an illustration of core principles of development, as far as I see it, "development follows transport" and "the main mode of transport shapes the form of development".
- The price of the building
- The price of the land
|A city with two subway lines|
However, though the urban neighborhoods are made cheaper, the zones around stations are made much more expensive than they were when they were "red", for cars only. Another factor to consider is that the rapid transit lines may make the downtown area even more attractive as it spreads and concentrates more things, which may make the downtown area more expensive than before, even as urban neighborhoods are available elsewhere and become cheaper.
So building rapid transit is a great way to relieve pressure on urban housing, so long as zoning is relaxed and the construction of urban areas is allowed rather than forbidden.
It works for sprawl too: highways and sprawl
|A city with two highways crossing its downtown area|
|Size comparison between the basic city (lower-right), the rapid transit city (upper-right) and the highway city (left)|
So highways help do the same thing for housing affordability in car-oriented neighborhoods that rapid transit does for urban housing affordability. Highways are thus a vital element of sprawling city to preserve housing affordability. A large city without highways but still car-oriented would also become more and more expensive over time as desirable land runs out.
I feel I must point out in all honesty that, yes, it does provide an explanation why the cities that have few or no highways near their downtown, like Vancouver, Toronto and San Francisco, all are afflicted with expensive single-family housing in their suburbs. Which may be caused by the lack of high-speed roads to the city itself, which restricts the land that provides an opportunity for development.
It would mean that, yes, building an highway right through Vancouver's downtown to the suburbs could effectively make suburban single-family housing more affordable by bringing closer all the suburbs to the downtown area and making new land available for development as they would become close enough to Vancouver's downtown. No, I do not recommend it as urban highways have much worse side effects on a lot of things, like the vibrancy of the urban neighborhoods they cut in two, but I do acknowledge that it is quite possibly a way to bring house prices down.
Note also that another possibility to deal with the issue is polycentricity, essentially build new downtowns to create urban neighborhoods around them too. It is quite possible. Tokyo is the best example, it doesn't have just one downtown, but many downtowns, all existing around stations of the Yamanote line (Shinjuku, Shibuya, Ikebukuro, Tokyo, Ueno, Shinagawa). However, tying these downtowns together with rapid transit is almost a must.