As seen in the screen capture above, the program highlights downtown bike trails (dark green) as well as streets with dedicated bike lanes (light green). When calculating directions the service has a preference for such routes, as well as streets featuring moderate elevation gains and light traffic.
Still, the Denver version of the program has at least one major glitch: It recommends cyclists cruise down the 16th Street Mall, even though the thoroughfare is usually off limits to two-wheelers. Some high-level Googler should go into the system and nix that route as an option -- or at least have the program offer pedal-powered scofflaws the fastest escape routes off 16th Street when the Mall Nazis come chasing after them.