They're there for safety as well, a common thing that happens with mobile home moves is trailer axles break and/or trailer tires blow out. The guys in back are there to alert the tractor trailer drivers of passing vehicles as well as potential problems, including but not limited to: interior fixtures coming loose and hitting the roadway, plastic coverings coming off the load, the load shifting, and any trailer issues. One of the escort vehicles also may or may not be carrying tools/supplies needed for the load and/or to deliver and set up the load. You'll also notice that all escort vehicles have some kind of flashing amber lights to warn motorists as well. if you blew a tire (or had some other mechanical mishap of any kind) on a trailer carrying a wide water tank or mobile home, that amber light is to warn other motorists to use caution and the escort vehicles are there to help assist the truck driver (and sometimes tow truck driver) with getting the vehicles on and off the road way to safety. The lead car also goes ahead in truckstops and towns to alert the driver of tight turns, obstacles (like curbs, signs, posts, and parked vehicles and more), and view parking area's for the rig. You'll typically notice wide/oversize loads moving toward the center of the road during curves and turns to prevent people from passing them in tight area's... or area's that could potentially become tight areas. They don't do that just for their safety, they do it for the safety of other motorists as well.
I used to live in Ocala, FL where they have 3 mobile home manufacturers. Other things, you'll notice some oversize loads can't go into just any area... due to an issue of ground clearence - so the escort drivers are watching for that as well. They get on our nerves from time to time, but have alot more to do than most think. I get on the CB and try to alert them when exactly I'm passing so the driver of the rig can anticipate me coming and drive accordingly.
You do Not want to surprise Any oversize load driver.
That's all, BBB