There are several problems with that.
First, in order to ride a train downtown to work a train must go from the suburbs to downtown. Metrorail doesn't and Metrorail's planned expansions will not. Houston's suburbs are 20-30 miles outside of the city and Metrorail, both now and 20 years from now when Phase II is complete, will not service any area more than about 6 miles outside of downtown.
Second, Houston's urban center is not heavily populated, never has been, and likely never will be. It's a decentralized city with low population density. Nobody lives downtown save a few highrises and apartment complexes. It would also be an inefficient use of land to build more apartment complexes or highrises there as doing so would consume more lucrative real estate from commercial and hotel uses. Therefore your assumption about rail being an "intelligent alternative" does not hold.
Third, it does indeed matter what city it is. Houston is not New York and New York is not Houston. Take an example: Building a subway system in Houston, for example, would not work even if New York has it. Why? Because Houston's land is clay-based and prone to flooding. Take another example: building an oil refinery near downtown NYC won't work like it does for Houston because there isn't nearby oil pumping into NYC to be refined. You'd have to ship it over long distances from somewhere else.
Second, Houston's urban center is not heavily populated, never has been, and likely never will be. It's a decentralized city with low population density. Nobody lives downtown save a few highrises and apartment complexes. All of Houston inside the "Loop" could benefit from a real mass transit system specifically because it is decentralized. It would also be an inefficient use of land to build more apartment complexes or highrises there as doing so would consume more lucrative real estate from commercial and hotel uses. If you built living quarters in the urban area you wouldn't need to transport the workers to the jobs, so therefore no need for extensive mass transit beyond the urban area. Therefore your assumption about rail being an "intelligent alternative" does not hold.
Third, it does indeed matter what city it is. Houston is not New York and New York is not Houston. Take an example: Building a subway system in Houston, for example, would not work even if New York has it. Why? Because Houston's land is clay-based and prone to flooding. No subway needed only "surface transportation". Take another example: building an oil refinery near downtown NYC won't work like it does for Houston because there isn't nearby oil pumping into NYC to be refined. You'd have to ship it over long distances from somewhere else. From personal experience; I, as a licensed "Tankerman" aboard an ocean going barge pumped crude oil to a refinery while looking at the Statue of Liberty and the World Trade Center under construction. That refinery was closer to Manhattan Island than Shell Oil's Deer Park, Tx. Refinery is to downtown Houston.
Ah, that would explain the 250,000 barrel per day Bayway refinery in NJ, directly across the river from downtown New York City!
Thanks you for your enlightenment of us, o wise one!
Ps. shipping over long distances - like from Venezuela, Angola, or Kuwait? You do realize that we import something like 2/3 of our oil? Ocean shipping, however, is cheap.