Shaw Metrorail Station entrance on the 700 block of R Street NW is an illustration of the opportunity to develop housing above certain stations

It's not Hong Kong and their MTR system which is known for integrating large scale real estate development into their business model, but in the city and certain other locations, there are opportunities for development above Metrorail station entrances that would add a bit of money to the revenue stream for the Metrorail system as well as more housing to the city.

More housing, eventually, results in lower housing prices, and in the meantime residents spend money in their neighborhood, contribute to the social and civic life of the city, and generate income and sales taxes, while rental property generates property and income taxes on the part of businesses.

While I just revisited the Hong Kong story, this post from 2014 is better.

-- "The success of Hong Kong Transit as "the exception" that proves the rule," 2014

From the piece:

Transit's success in Hong Kong is the result of having (1) a densely populated place; (2) constrained by geography, making automobility and sprawl difficult; (3) "mixed land uses" rather than separation; (4) tight links between transportation planning and land use planning; and (5) a commitment to building and extending a multi-modal transit system to simplify mobility.

... Transit failure isn't hard to figure out. Deconcentration of land use, population, and employment centers with a focus on separating uses are all of the conditions that militate against successful transit. That's why Hong Kong is a good example for us.

Of course, New York City is an exception to the post-WWII general trend of US transit failure, which proves the rule about concentration, mixed use, and transit.

WRT NYC, the book Green Metropolis provides a good overview of the environmental advantages that are derived from these characteristics. New York City is the "greenest" city in the US in terms of lowest per capita energy use, lowest car ownership, lowest use of gasoline, lowest GHG per capita, lowest waste production per capita, etc.

DC's transit success is based on job concentration at the core. That transit does reasonably well in DC in a land use paradigm that still preferences automobility comes down to three things (1) concentration of jobs at the core, required by law (federal agencies); (2) the federal transit benefit which pays for a goodly portion of getting to work for many people; and (3) the proximity of DC residential districts comprised of attractive historic building stock to the employment centers in the core, which has allowed much of DC to revitalize [and intensify, relatively speaking] despite sprawl.