Comparing a public transportation right of way to an extra traffic lane shows that it typically carries 20% of what the traffic lane would carry...
There are some land locked major cities where it is a very sensible use of public money. But the urge of the next 50 cities in size to...Adding an extra lane merely funnels more traffic onto the connecting roads and streets that haven't (and likely can't) been expanded. It also increases the burden on limited parking availablity. The urban centers of most major cities are "landlocked", that's why they're "cities" -- the land has been fully developed and availability is at a premium. Mass transit is the most sensible means of moving people around in these densely populated areas. Yes, including commuting from/to the 'burbs and out to the airport.
Yes, I agree in some instance it is the most "sensible" but should it be a Planned Outcome. Should government take property (tax) to finace planners dreams, or is the invisible hand going to give us the solution that people want anyway?
Remeber: Large city governemtns, almost universally under socialist-democrat control, will be the ones making the decisions.
We are way off topic....I'll try and post a thread about this with a lot of links and ping you to it when I start it...but I don't know when I will have the time.