I'll be honest: I don't really see the point of this rolling bridge. Sure, it's a pretty sweet idea, and it looks really cool, but how often do you need to roll a bridge up into a circle? Sure, it makes it easy to transport, but it's not like bridges are always needing to be moved. Generally speaking, once a bridge is in place it stays put.
But hey, I'm no engineer. The rolling bridge was designed to roll up by being built with eight segments, and I guess it could be used as a replacement for a drawbridge. Whatever, I still don't get the point of it all.