The 20th annual Congress for the New Urbanism was held this week in West Palm Beach, Fla.  Such anniversaries are an occasion for reflection on past accomplishments, and also for looking ahead.  One of the most exciting topics on the docket was “tactical urbanism,” the movement of incremental, small-scale – usually temporary, sometimes unsanctioned – improvements to the built landscape.  One session featured Ralph Rosado, of C3TS, who presented on a project that turned a parking lot along Miami’s Biscayne Boulevard into a park for a week.  Russ Preston, Design Director of the Principle Group, described how informal outdoor movie projections activated a neighborhood (and eventually became sanctioned by Paramount Pictures).  Ellen Dunham-Jones, of Georgia Tech, described how her students installed temporary bike signage, historical markers, and storytelling benches to downtown Lithonia, Ga., to help catalyze long-term change there.   The session was emceed by Mike Lydon, principle of Street Plans Collaborative, and lead editor of the Tactical Urbanism manual, volume 2 of which was just released.  Following the session, Lydon stepped aside with EngagiesCities to discuss the past and future of tactical urbanism.