Duke’s own campus transportation system is well-run, extremely safe, clean, efficient, and free. Some of the bus drivers are obviously not excited about driving around a bunch of college kids on the same route day after day, but who can blame them? At peak times, the buses can get quite crowded and, thus, uncomfortable, and the reduced schedule between East and West on the weekends can get annoying, but, on the whole, the buses do their job well.
Duke students hardly ever use the Durham-run modes of public transport, as they are generally inconvenient, unreliable, and, at times, unsafe. The Duke system is extensive, and you'll rarely want more transport options around campus. Most students carpool or take a taxi if they need to get to the airport, though the University does schedule shuttles before and after major breaks. Many take the Robertson Scholars bus or have a friend drive them if they want to get to Chapel Hill. For movies and restaurants, students normally walk or drive their cars.