jack braking

[Rudolph C Troike]

I'm guessing that the meaning of "jack braking" is the same as that for
"jake braking" given recently, but I'd like to know if anyone can confirm
it. I encountered the term on a sign on a highway in western Oklahoma,
miles from anywhere, and couldn't see any particular reason for it other
than that the terrain at that point was a roller-coaster series of hills
up and down. However, I'm not sure from the description of "jake braking"
given why there would be a prohibition against it in such wide-open
spaces. I inferred from the description that it might be objected to
because of the noise, but this obviously does not apply here. I'm still
wondering why it was proscribed in this context. Could it be dangerous?

        Rudy