It’s quite common for a really heavy load to have one or more push trucks behind it to push when going up inclines.  Push trucks are commonly used on the Dalton Highway as well as the Parks and Richardson when the loads are outrageously heavy, otherwise it would take a very long time and so much fuel for the truck with the load to get up a mountain, and it would also impede traffic for long periods of time.  The push trucks just follow the load when not going up hills.

Taken 11 years ago, these photos really show how close Jack’s push truck gets to the load he’s pushing (a crane).  You can see the pad that the push bar pushes against, how the trucks make contact.