This LCV combination, like the ‘turnpike doubles’ requires extra driver training. Lengths of the trailers used with this combination vary, and different axle configurations vary much more than those used with turnpike doubles. The 9 axle combination shown here is shown as an example of the type of axle configurations available with a Rocky Mountain double. The Rocky Mountain double is a truck configuration that is operated on more highways than turnpike doubles and triples are operated.