The modern streetcar is front and center for the next phase of downtown revitalization.

This year, 435 employees will move into the new, nine-story UniSource Energy/Tucson Electric Power headquarters. By April, Buffalo Exchange will open up a shop on Congress Street and the Sonoran Institute should be in 44 E. Broadway.

Also on the horizon, as many as three towers of university student housing could go up around the Rialto Theatre, and a hotel is part of three proposals for mixed-use development for an eight-acre strip, where the temporary Greyhound terminal stands along the Interstate 10 frontage road.

No doubt, though, streetcar construction will be the defining event for the next two years as 3.9 miles of tracks are slated to be installed from mid-2011 through early 2013. The tracks would connect University Medical Center, the University of Arizona, University Boulevard, Fourth Avenue, downtown and the near West Side.

The streetcar would travel to the West Side across a new Cushing Street Bridge, which should start construction in spring and is slated for completion in mid-2012, said Michael Barton, project manager for HDR Engineering.

Most eager to see a streetcar in motion, is Jerry Dixon, patriarch of the family enterprise behind the Mercado District of Menlo Park and Mission District. The streetcar and Cushing Street Bridge would feed into his developments on 30 acres, along with another 35 acres of city property once envisioned as a museum row.

"By building one bridge across the Santa Cruz River, the city effectively doubles the size of downtown, giving access to 65 acres," Dixon said.