Hi, you also find them in a lot of car parks, were they operate the barriers. If you find yourself stuck in a car park etc, you can usually approach the barrier from the wrong side/direction, walk through, slide a shovel or drag a chain over the loop, and the barrier will open and off you go. If you do this be careful, in the wrong place, or reason it could get you in to trouble.
Peter when i was in College , i used to do a bit of security work on the weekend and i can remeber us having to open barriers like this when we had a drama with them
Flip