Originally Posted by Oaklevel
Different tunnels / states have different rules. Some you do nothing, some you turn the gas off, some you can not go through at all. Check your route before you leave.
I see that you're in PA. The PA turnpike's rule is that the tanks are supposed to be off (just closed at the tank). You don't have to actually disconnect any hoses or anything like that. I've never been stopped and asked. And, I've been through those tunnels many times with my tanks on (before I knew the rules).
The tunnels in Baltimore prohibit any propane tank greater than 10 lbs. If you're stopped and checked, supposedly they'll make you exit into the city which would be a mess to deal with.
The Virginia Chesapeake Bay Bridge Tunnel makes you have them off and they'll ask you at the toll. If it is on, they'll make you stop and turn it off.
So, like said- different rules for different roads and tunnels.