The axles steer when loaded, to make sharp corners. It all folds up on top of itself in 3 layers when it's empty. They moved a massive turbine through here on I-40 several months ago, and I had the pleasure of driving along side of it to take a really good look when it came through empty.
This is the way I saw it, with sections on top, and the trailer narrowed to fit into just over one lane. With the load on it, the axles will spread to stabilize the big load. It took up 2 1/2 lanes and 11 days to make it up to Virginia. When they got to certain overpasses that it couldn't clear, they would get off the exit and go straight across to the entrance to continue.
When they got close to Knoxville, a police escort joined to get them through the populated areas while closing the ramps to other traffic.
Here's another folded unit, empty.
[ame="http://www.youtube.com/watch?v=O0663asT5xY&feature=related"]YouTube - 1.9 Million lb generator move by Mammoet through Johnston, SC‏[/ame]
4 road tractors, 2 pullers, 2 pushers.