UC Davis senior Devin Braun has more reason than most of his peers to be precise about time -- he helps run the bus service they rely on. As operations manager for Unitrans, the German major is responsible for the day-to-day operations of the bus system that serves the university and the city of Davis -- and is believed to be the largest public transit service run by students in the United States. About 175 student employees -- including 130 drivers -- and 15 career employees operate a system that carries 16,000 to 18,000 passengers each weekday in up to 30 buses over 15 routes. "It's a unique system," says Jim McElroy, who began working as a student driver in the early 1970s and is now the general manager. "It's heavily dependent on students doing almost everything that it takes to run the system." Career employees are responsible for maintenance, safety, long-term planning, and budgeting and finance. Student drivers, who must obtain a Class B commercial license with a passenger endorsement, receive 15 hours of classroom instruction and 25 hours of training behind the wheel. Braun says the attraction of the operations manager job is the challenge of dealing with everything at once, from ensuring policies and safety procedures are followed to making sure each bus has a driver and supervising other students who troubleshoot along the routes. In addition to serving 15 hours a week as a manager, he signs up for about 25 hours a week as a driver or conductor.