The Bridge at Arles was a hand-operated lift bridge. The beams at the top of the towers were weighted so they could swing up (over the channel), lifting the bridge deck out of the way (and blocking the roadway).
The Glengall Bridge isn't as evocative as the Bridge at Arles. Still, it's amusing once you are aware of the resemblance. However, I don't see a mechanism on the Glengall Bridge for lifting the deck. Perhaps it's not a working copy.
There's a lot of information on The Bridge at Arles on the Internet. I found an interesting blog by John Vanderslice that includes a photo of the bridge in the 'up' position.
Great Britain: Glengall Bridge by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.