Prototypical Plausibility, or the C-P-R Principle

Would a CP Rail SD40-2 ever lead a VIA
passenger train? The C-P-R principle says yes.

The C-P-R principle--that's what my friend Eric Gagnon suggests to help modellers determine prototypical plausibility.

The subject came up on the Candian Model Trains group on Yahoo! during a discussion about whether it might have been possible to find CN and CP Rail F-units mixed together on VIA Rail passenger trains during VIA's early years.

The issue got Eric thinking. "It would be useful to have some sort of an index, matrix or principle to determine whether a given practice ever happened," he wrote.

It's too easy and not really meaningful to just say yes, it happened, because someone saw it in a magazine once, read it online or heard it from a friend, he added.

Besides, that's not the real question, Eric wrote. The real question is: "Can I realistically model it as a practice that exceeds one-off status?" And: "Is there proof that I can rely on, to assist me in my modelling?

For Eric, there are at least three factors that need to be addressed. He calls this the C-P-R principle: Context, Probability and Records (C-P-R).

Context: When and where? Which specific era? Which location or area?

Probability: What likelihood was there, day in and day out, that the practice could be seen by a trackside observer during the era in question?

Records: Are there photographic or other first-person observations to illustrate the practice? If it did happen, how relevant is it to realistic modelling, if that's the questioner's aim?

In answer to the question that started it all--if CN and CP Rail F-units might have ever been seen together at the head of a passenger train during VIA's early years--Eric says yes. The probability is excellent, and there are photographic records.

On the CP Rail M & M Sub., my goal is plausibility--is it likely that a certain locomotive or piece of rolling stock might be found in Manitoba and Minnesota during the early 1990s? Up until now, I've gone mostly with my gut, and the little bit of knowledge I have of that era and locale. But now I might also be able to use C-P-R, too.

Thanks, Eric.

(Photo from Trackside Treasure.)