I didn't mean to imply that Houston's 7-1/2 mile light rail line was the end-all be-all. It's a start, however. You have to start somewhere. Even DC's extensive [[and very busy) subway system started as a short link between Rhode Island Avenue and Farragut North. [[
http://wmata.com/rail/maps/map.cfm?). Thirty-six years later, with eventual expansion, the system has changed how that region lives, works, and travels, and has resulted in billions of dollars of pedestrian-oriented development that is proximate to transit.
Right now, Detroit needs a start.