A relatively new truck driver was engaged in transporting rock from the underground blasting area in a mine to the surface. He was still in what has been referred to as a "training position." He stopped to talk to several other workers, one of whom was driving another piece of heavy equipment - a scoop loader. The truck driver parked his vehicle approximately 10 feet behind the loader and set the electric parking brake with the toggle switch. Because of the limited space in the underground tunnels it is normal practice to enter equipment from the front end rather than the sides. […]