Bill- You are writing about what was/is called "emergency guard rails" as differentiated from guard rails on switches, crossing diamonds, etc., that serve to keep flanges aligned. Emergency guard rails are generally used on through- plate girder or truss bridges, or other structures which have strtural members above the top-of-rail, and on some railroads nowadays not on open deck bridges (although they probably should be) andthey are used to protect structures that are close to the tracks which might be damaged by a derailed car, such as a tunnel portal. I have never seen them outside of the running rails, so can't comment on why they are that way at Casacde. A guess- Maybe they weren't reinstalled after changing of ties?? Ned