The concept of large trucks underground has been around for some time. While the road train concept is gaining momentum, there are underground mining applications where these trucks have not been suitable. Unfortunately few of the 'greenfields' projects that are most suited to the road train concept have come 'on line' since the underground road train was first introduced to Australia in 2001 so that the trucks have generally been adapted to existing operations. As at December 2004, there were 17 road trains operating underground in Australia, one being rebuilt and one under construction. This paper addresses the necessity for the mining industry to have an integrated ore transport system that starts at the underground load haul dump unit (LHD) in the stope production area and finishes at the crusher feed at the processing plant. Chute and orepass designs are investigated, as well as feeders to determine the best load and haul system for large-scale trucking. The paper also discusses potential developments in the large truck scene. These include: the concept of a road train prime mover that has a capacity of 32 t (side dumping or rear dumping) and is suitable for being loaded in development headings; the use of hydraulic drives in large underground trucks to provide same speeds in forward and reverse; the development of a 'push-pull' road train system that removes the need for truck turning loops (trucks can either side dump, bottom dump or rear dump); the use of side-loading buckets for loaders; and the application of automation to large underground trucks. The paper highlights the cost and productivity gains by introducing large trucks and associated integrated ore transport systems underground. While 400 vertical metres was seen as the limit of vertical hauling in the 1970s, one kilornetre is a common discussion point for trucking limits today. In real terms the cost of underground trucking (including ownership costs) has decreased from $1.50 - $2.00/t.km in the mid-1990s to $1.00 - $1.20/t.km at present.
