: Use Cobblestone Walls or Iron Bars to create a vertical pole.
: Use Sticky Pistons buried underground to push up Fences or Cobblestone Walls when a train is detected, creating a physical barrier.
If you just want the look without the complex wiring, you can use these materials for a classic signal: Minecraft- Railroad Crossing
: Connect the detector rail signal to a Redstone Clock (a simple loop of repeaters). This will make Redstone Lamps flash on and off while the train passes.
: Use White Concrete or Quartz to create an "X" and "RR" symbol on the road surface about 10 blocks before the tracks. : Use Cobblestone Walls or Iron Bars to
Vanilla Railway Crossing (A "How to build a" Minecraft Tutorial) YouTube · Railway Janni Minecraft UK Level Crossing Tutorial YouTube · CraftyFoxe Minecraft Railroad Crossing Cantilever Tutorial 2020 YouTube · CraftyFoxe Minecraft Railroad Crossing Tutorial
: Place Red Stained Glass in Item Frames on either side of a block at the top. This will make Redstone Lamps flash on and
Watch these tutorials to see different styles, including modern US signals and functional vanilla redstone builds: How to Make a Realistic Railroad Crossing in Minecraft YouTube · French Fried Trains