How do you not see the sign? Stuck on RR tracks.

Because a lot of these routes predate big trucks. And due to that there is a lot of built up infrastructure around these areas. You could lower the rail or raise the road sure. But in many cases the rail is raised for a reason and lowering it could and would cause issues for the train, some.of them of the "will damage the train" varity. And raiseing the road to a point you wont high center a semi is logistically imposible without demolishing a lot of currently standing stuff or as CD pointed out moving a ton of utilitys, things like water drainage and sewage needing to be rerouted entirely since sewage doesnt flow uphill well.

Hell some of them you would need to move the entire main road to get enough room to build the ramp.or building a ramp would cause all kinds of water run off issues that would require all kinds of drainage infrastructure to be built to control. Most of these crossings would be tens if not hundreds of thousands of dollars a pop MINIMUM to "fix" and even more to maintain that type of ramp and road. Hell some of them would run into the millions or 10s of millions buying up the land so you even CAN. Even with abuseing iminate domain which is going to absolutely infurate your tax base and may lead to many of them and their businesses just leaving.

Meanwhile putting a sign up, and putting the info into all kinds of databases telling trucks to go a half mile up the road to a more suitable crossing and expecting a PROFESSIONAL driver to know his #### route only costs a few hundred bucks and should be the end of the issue.