San Francisco's Municipal Railway (a.k.a. the MUNI) provides not only "transit service within the city and county of San Francisco 24 hours a day, 7 days a week" but also numerous bases for potential legal actions.  It's a veritable legal clinic, offering case studies in personal injury, possible ADA violations, and criminal assault—in just the last month alone.  Innocent pedestrians, riders, and even bus drivers themselves are at risk:

• S.F. to pay $21 million in traffic death (San Francisco Chronicle, 03/05/08).
• Woman in Wheelchair vs. Muni Bus Driver (ABC 7 News, 02/01/08).  See also What does it take to get fired from Muni? (ABC 7 News, 02/01/08).
• Attacks may force Muni to suspend some bus service: Drivers, coaches in Hunters Point targets of violence (San Francisco Chronicle, 03/05/08).