6 trucks transporting a 300-ton generator - GIF

[Frank S]

well I can't speak for 6 but I can for up to 3.
Part of your answer is yes there are times when 1 will be just dragged along when there is little or no need for the extra power the driver might even have his unit in neutral only being there for the steering and braking force
the biggest problem with multiple power units IE tractors is each one of the puller or pushers must also carry weight mass usually heavy enough to equal the legal axle loading allowed. here in the States that is 34,000 lbs total weight on the tandems
when under a hard pull shifting up or down with multiple power units must be sequential so that there is only 1 out of the many out of the power transmittal at a time I shift you shift he shifts then she shifts one hand will always be near the mic to relay instructions. When all are pulling not changing gears the gauges become your best friend you can tell b y the amount of boost pressure you are developing in relation to the amount of power you are applying to the ground. plus if you are an OD (over dimensional) hauler with any experience at all you can feel when your unit in the chain is carrying its load the guy in front or behind you will tell you if you are adding too much or too little by the way their rig feel to them as well.
We used to regularly move an intact drill rig without the draw works and power head from location to location by backing 1 truck under the front of the substructure then backing 1 under the rear then lowering the derrick on to a tower mounted fifth wheel on the front truck the guy under the derrick did the navigating and set the pace usually very slow since we were going across country not on any roads only crossing them when they were in our way. the guy in the rocking chair (the middle) truck under the substructure just pulled his guts out while the dogs tail had to wag while while driving backwards the whole weight or the rig was on the trucks not on a fancy 50 axle 200 tire steerable trailer we carried everything on 3 5 axle oilfield trucks. 25 ft tall 20 ft wide and 170 ft long the skids of the rig only a few inches off the ground sometimes plowing the ground