Wet roads is an dynamic shader. There's even version with real-time generated rain drops, but it's not released (and probably won't).
About xrParticlesEditor: if there's not much particles, even potato can handle it well. But, as i said, it can be used only for certain places, not the whole map (yeah, it's not a shader).
About xrParticlesEditor: if there's not much particles, even potato can handle it well. But, as i said, it can be used only for certain places, not the whole map (yeah, it's not a shader).