Busses, like trains, taxies, airport shuttles and similar services that carry passengers for a fee are “Common Carriers”.  As such, bus companies have additional duties under the law, and owe a higher duty of care to provide safe transportation for their passengers. The must take preventative measures to protect passengers in the event of an emergency.
Common causes of bus accidents, in addition to breaking the rules of the road such as speeding and distracted driving, include defective or improperly maintained equipment, improper or inadequate training of drivers, negligent hiring or supervision, and failure to have adequate weight distribution.