Do mass transit accident victims have to file a class action suit or all use the same attorney?

In a mass transit accident, even if there are many victims who are injured at once, each one will have a different legal case because of factors such as where the injured person or fatality victim was seated with relation to the impact of the crash, how long he or she suffered, and what losses resulted to the victim or the victim's family.  Victims can each use whatever attorney they choose.