Engineers are by nature a conservative lot. Buildings and bridges are designed to withstand loads from the expected and the unexpected. The same is not done when designing pavements: unexpected traffic volumes sabotage many designs. Given the current trends, one thing is sure: the design of 20 years ago will not last 20 years under today's traffic. Yet antiquated standards continue to be used.
One of the reasons for doing things the old way is not understanding the new way. That may account for some engineers using the same pavement designs they used 20 years ago. Parts of the 1986 AASHTO pavement design guide are complex and difficult to understand. To make analysis easier, we've taken the 1986 AASHTO pavement design guide and simplified it using the power of the microcomputer.