Train level crossing using 2021 road plates
It occurred to me that you could use 8-stud-long tiles, tilted ~3 degrees, resting on plates at different heights.
Side view from a quick LeoCAD mock-up:

Since clipping the tile to plates at different heights might stress the tile, I suggest to place it resting on top of tiles at different heights.

Edit: After several iterations, I think the ramp should be better made out of 2x4 tiles, resting on top of tiles at the railtrack side, and free-standing at the roadplate side, like so:


That's trivially built with 1x4 tiles, 4x8 plates and 1x8 plates.
There are variations of this kind of ramp, depending on the parts available. For example, the following uses 15068 2x2 Slope, curved instead of tiles. I'm assuming the slope would help the ramp to slide in place a bit better, plus the 2x2 plates help the ramp to not slide alongside the track:

Note, in the image above, how the tiniest bit of yellow plate is visible to the right of the blue slope - that means the assembly is so slightly over 8 studs long (when tilted), which makes it pretty much impossible to use hinges for the ramp.

A similar anti-slide arrangement can be made roadside. I suggest using 32028 1x2 plate with door rail, on both sides of a 1x10 plate, with tiles on top, like so:

I guess that could be easily replaced with &quot;1x1 plate with teeth&quot;.