Derailment will come under accident class C.
Accident class C is defined as “An accident involving a train that results in the death of one or more persons or the serious injury of one or more persons.” Derailments can cause serious injuries and fatalities, so they are classified as accident class C.
Accident class A is defined as “An accident involving a train that results in the death of one or more persons.” Accident class B is defined as “An accident involving a train that results in the serious injury of one or more persons.” Accident class D is defined as “An accident involving a train that results in the minor injury of one or more persons.”
Accident class C is the most serious type of accident, followed by accident class B, accident class A, and accident class D.