This is not an easy question to answer due to the potential variables. In some cases, a bus driver may cause the accident, maybe the manufacturer if it built a defective bus, the company responsible for the maintenance of the bus, the company or municipality responsible for driver training and hiring, and potentially the crews responsible for maintaining the roadways a bus travels on. Bus accident liability can be complicated, and this is why you need to work with an attorney who has experience handling these types of claims.