Term "Key Train" ?

[NSSpike]

Recently an NS manifest train was having extreme power problems and struggling to maintain 5mph. Kept stalling out.  With two Dash 9's and an SD 70. The crew was instructed to cut the train at a road crossing and tie down their train and be on the lookout for the road forman. The crew stated "you are aware that this is a key train" after a short pause.... "Have road forman X call me when he gets there. What is meant by "key train"?

[florida581]

I'm pretty sure the requirements of a key train are the same on any railroad.  I found this definition:

A "Key Train" is any train with:
* one tank car load of poison or toxic inhalation hazard (PIH or TIH) (Hazard Zone A, B, C, D) or anhydrous ammonia, or;
* 20 car loads or intermodal portable tank loads of a combination of PIH or TIH (Hazard Zone A, B, C, D), anhydrous ammonia, flammable gas, Class 1.1 or 1.2 explosives, and environmentally sensitive chemicals, or;
* one or more car loads of Spent Nuclear Fuel (SNF), High Level Radioactive Waste (HLRW).