Although I live in Mesa, I work in Downtown Phoenix, right on Central Ave. I can see that, even during rush hour, there is relatively light traffic on Central, and the traffic-light cycle favors Van Buren. I suggest making the entire street, from just south of Jefferson to McDowell a pedestrian-only zone, with shade trees (adapted to the desert), other landscaping, street furniture etc, and designing it so that it can accommodate street festivals similar to First Friday. First Street and First Avenue are wide and underutilized; make them into one-way streets to take the traffic that would be bumped off Central. Keep one narrow lane for the Express bus routes. (It doesn't have to be asphalt; it can have the texture of the rest of the pedestrian zone). Build a banister between the street and the light-rail tracks. Every European city of decent size has such a zone, but closer at hand is Denver, where they've converted a mile-long street in the heart of their Downtown into a very successful car-free zone.