Trap Doors/ Hidden walls

I thought of a cool dungeon/ horror type thing for rides. Would work cool on dark rides mostly, if we could have like built in walls or hidden doors that open like ride events. The thing is you wouldn't really know they where there. Obviously when your building your ride you would know but when you actually ride it or have guests ride it they think they are going to crash into it. Could work for floors too, EX: you fall into sewers or into elevator type thing and do an insane drop, but the initial way down is blocked from your view. Just a thought, if theres already a post about this i didn't mean to double post.