What are the guidelines for rail accidents?

Explanation:

FRA investigates accidents and incidents as determined by the Accident Analysis Branch or regional management. Generally, FRA investigates accidents and incidents meeting the following criteria:

Any collision (main or yard track), derailment, or passenger train incident resulting in at least one fatality or serious injury to railroad passengers or crewmembers.

Any railroad-related accident resulting in death to an on-duty railroad employee, including an employee of a contractor to a railroad, regardless of craft.

Any highway-rail grade crossing accident resulting in any of the following:

Death to one or more persons being transported in a commercial vehicle or school bus.

Serious injury to several persons being transported in a commercial vehicle or school bus.

Death to three or more persons in a private highway vehicle.

Accidents involving grade crossing signal failure or allegations of grade crossing signal failure.

Any non-casualty train accident resulting in derailment of a locomotive, 15 cars or more, and extensive property damage.

Any train accident/incident resulting in a fire, explosion, evacuation, or release of regulated hazardous materials, especially if it exposed a community to these hazards or the threat of such exposure.

Any accident/incident involving a train transporting nuclear materials.

Any train incident involving runaway or rollaway equipment, with or without locomotives.

Any collision involving maintenance-of-way or hi-rail equipment.

Any accident caused by failure of a locomotive or any part of a locomotive, or a person coming in contact with an electrically energized part that resulted in serious injury or death of one or more persons.  

Accidents resulting from signal failure including Positive Train Control-related failures and malfunctions.

Any other train accident/incident likely to generate considerable public interest.

Most Amtrak accidents/incidents.

giant impact theory - the moon was formed from the collision between earth and another mars-sized body.

colliding planetesimals hypothesis - the moon was formed from the same cloud of material as earth.

capture hypothesis - the moon was locked into orbit by earths gravity as it was passing by it.

accretion hypothesis - the moon was formed from collisions and combining of planetesimals.

i think this is right, if not and you know better let me know.

answer; participant observation method;