Funnily enough, I had a timeline flickering half-hour just this weekend past. I had a half-hour drive to get to my destination on a main thoroughfare, but not the high-speed freeway. Up in the distance I saw a mining convoy consisting of 2 oversize/over-mass mining equipment being hauled by trucks, with quite a backlog of ordinary traffic stuck behind it. Normally the speed limit on that road is 100kmh, I was doing 80 to 90kmh and I estimate the truck convoy was doing about 30-40kmh. Before I could catch up with the slowed down traffic, I saw it turn off to the right to an industrial area at a traffic light and disappear. Great, I thought, I am not going to be slowed down after all, that was lucky! But slightly further up the main road I again saw it ahead of me, again with traffic backed up behind it. OK, I thought, that's odd, but let's see how long it takes me to catch up to it this time (and I continued on at 80-90kmh).
Then a long curve of the road hid the convoy from me, and when I came around it, I was just at the lights of the turnoff to the main freeway. The convoy had gone, so I assumed it had turned off there. I could see straight ahead and it was not there. So I carried along the main road, only to catch sight of it much further ahead, and this time it was turning at a large roundabout, going very slowly, and travelling in the direction I needed to go. Bear in mind I had not been slowed up by this thing yet, at all.
I made my turn on the roundabout, and by now the speed limit on the road had revised to 70kmh. Therefore, by rights, I should have definitely caught up and been slowed down by the slow-moving convoy. It was taking up 2 lanes of road, so nothing could get past it. But lo and behold, it was vanished and gone forever, and I never did catch up with it.
By the way, the equipment being hauled was about 3 times the size of these tyres. The one in the rear of the convoy (the closer one to me) was big and square, bright yellow, and top heavy, with flashing yellow lights all along its top edge. There is no chance I could have taken it to be anything other than what it was. As I caught sight of it on the roundabout, I saw the profile and it was a massively long-haul semi trailer, like a 3-trailer hanger. I was alone in my car except for my dog, so had no-one else for confirmation unfortunately, but I know what I know!