Here is a question: why hasn't Denver looked into using cable cars for the downtown area - primarily the 16th Street Mall and the surrounding loop? I was wondering about this after visiting San Francisco over the weekend and seeing how cable cars were maintained by the city. BTW, I'd recommend visiting the cable car museum for anyone in the SF area.
It's really old technology, but works extremely well, especially when you consider it's the same method used on Ski Lifts to move people up the mountains. However, instead of the insane hills of San Fran or the mountains, we have relatively flat areas of city to traverse. In other words, the torque required to move the cables would be much lower.
All that would be required is to dig a small tunnel under the mall to insert some pulleys underground and add a generator at one end of the mall. Then, whether the city wanted to utilize rail cars - or even a vehicle on wheels - the moving platform could then clamp down on the continuously moving rail to go forward - or conversely de-clamp from the rail in order to stop.
This would get us away from using buses and would be an eco-friendly method of moving people around the city. Plus, the city wouldn't have to install unsightly electrical wires overhead, which would be a huge advantage esthetically. Not to mention, it's a quiet and clean propulsion system and could get us away from carbon-emiting plumes of exhaust that we currently encounter when passing by.
Currently, San Fran is the only city in the world that still uses cable cars. However, if it's good enough for them and good enough for our ski resorts, why can't it be good enough for the mall? It could easily move people up to 20 mph and would be a great "attraction" to downtown visitors. Of course, it wouldn't have the historical significance of SF, but it would still be a draw. Why not consider it?