No, but as I pointed out in my train example above, when I get on a literal railroad(train) and go somewhere, I still have lots of choices while on that railroad. Having choice while being forced down a lane or having choice AFTER you are forced down a lane, doesn't remove the railroad.
I usually have about a half dozen pre-made encounters ready. If the party goes out of the prepared area and into the unknown and say comes to that fork, I will generally pick one of those encounters that fits the area and place it down one of the paths. Once I place it, though, I cross it off and will not re-use it later if the party picks the other fork and never encounters it.