As the passenger on a bus you put yourself in the care of the bus driver who is employed by the bus company.
If an accident occurs whilst you are on a bus then you may be entitled to compensation.
Now this can be two-fold. The compensation may be payable by the bus company for the negligent actions of the bus driver as their employee, or alternatively, if it was not the fault of the bus driver then another vehicle may be at fault and therefore it may be possible to recover compensation from their insurance company.
If the accident was caused by the fault of a vehicle which has subsequently disappeared then there may be a claim to the Motor Insurers Bureau.
In these circumstances you should get as much information from the driver of the bus and any passengers on board and the matter must be reported to the police.