Tucson's <answer>Sun Tran</answer> bus system serves greater Tucson with standard, express, regional shuttle, and on-demand shuttle bus service. It was awarded Best Transit System in 1988 and 2005. A 3.9-mile streetcar line, Sun Link, connects the University of Arizona campus with 4th Avenue, downtown, and the Mercado District west of Interstate 10 and the Santa Cruz River. Ten-minute headway passenger service began July 25, 2014. The streetcar utilizes <answer>Sun Tran</answer>'s card payment and transfer system, connecting with the University of Arizona's CatTran shuttles, Amtrak, and Greyhound intercity bus service.
What is Tucson's bus system called?
Sun Tran