New Term in Railroad Jargon?

The TRAINS Newswire of this date 2 Jan2014 : carries the following story:

"Broken axle focus of investigation of BNSF oil train wreck, line reopens"Published: January 2, 2014

“We’re a key train!” the engineer of the oil train said frantically, before yelling at the conductor “Get out!”

“Dispatcher, emergency. We are everywhere, key train, we are on fire!” the engineer said before leaving the engine…"

My interest is in the term: " Key Train"

Over the years I’ve heard of many terms to identify specific trains(or types of trains), and they seem widespread in the jargon of th****e industry.
This is the first time i’ve ever heard this one, or seen it mentioned in conjunction with the railroad industry.

Could someone please explain its use, and origins?
Thanks!

Could it be short for Keystone oil?

“Key Train” is used by a number of railroads to designate trains with a certain number of hazardous cars. On BNSF it is 20 hazardous cars or five toxic inhalation hazards.

http://boe.aar.com/boe/download/circular_ot-55-j.pdf

Definition starts on the third page. Pertains to what a Key Train is, and operational requirements.

thanks for an excellent posting and reference,

"…Posted by on Thu, Jan 2 2014 11:14 AM

“…“Key Train” is used by a number of railroads to designate trains with a certain number of hazardous cars. On BNSF it is 20 hazardous cars or five toxic inhalation hazards.=…”

Brian Schmidt, Assistant Editor Trains magazine

Thank You Zugmann and Brian…

For those of us without scanners,and regular conversations with RR personnel; sometimes we get surprised by new terms, as was this case for me. [:-^]

Key Train is a term that has been used in the industry for at least the past 15 years. With the MMA’s troubles in Quebec additional restrictions on the handling of Key Train have been implemented by the FRA, the restrictions relate on where and how a Key Train may be tied down and have the crew removed from the train.

“Key train” designations go back before 1989.