Is it just me, or is this obvious? Subways have proven over and over to be the most economical and least objectionable mode of mass transit wherever density is high enough to support them. Any place where subways are viable should have them - buses, trolleys, and light rail are not a substitute. It follows that any place with growing density needs to build more subways, even if that means eternal construction. Besides, subway construction is hard to get upset about, being mostly underground. It&#x27;s far less disruptive than tearing up streets or surface level rail.