Maybe less highwaymen and more a local baron suddenly levying a toll on a major road. That sort of thing happened a lot, and never failed to upset merchants who

Maybe less highwaymen and more a local baron suddenly levying a toll on a major road. That sort of thing happened a lot, and never failed to upset merchants who would protest with a higher authority. Except in this case there's a random aspect to the toll, and you can avoid the toll by knowing the situation and lowering your speed in time. I'm pretty sure the locals are all familiar with the situation and know how to avoid these fines.