During my years as a transport manager, I took a driver out on his first day with us, to show him the routes and deliveries. He was fine, driving to the warehouse when the truck was empty but once loaded, he had no idea! He came directly from a retraining scheme that taught people to pass an HGV test. He had never driven a loaded truck! I had to spend a lot of time with him and I was glad that I did. He did not appreciate being "shadowed" at first but thanked me in the end. In terms of "speed awareness" he learned to appreciate what speed was appropriate for the road conditions and the loading of the truck.
