A road is not just a simple, standalone item.

It is comprised of a number of different components including signage, culverts, guardrails, etc.  Knowing all the pieces makes long term maintenance planning much easier, plus it allows you to demonstrate exactly where, and how much, specific funding is allocated.  This plan can also highlight specific weaknesses your operators may have with the operation of their equipment, thereby allowing for specific training to be scheduled.

The bottom line is a road must be looked at from many different angles in order to ensure its longevity.