Christian Y. Agnew, P.E. & Mark J. Farrow, P.E.

Most large cities are currently using pavement standards developed decades ago based on traffic projections that did not accurately predict the amount of heavy trucks and buses on our roadways today. Pavement sections that once had a 20 to 25 year design life years ago now have a serviceable life of less than 10 years. This is typically confirmed when pavement design studies are performed for major municipal roadways receiving frequent heavy truck and/or bus traffic. Non-destructive tests (such as FWD) performed on existing pavements of many large cities show lower than expected serviceable pavement lives.

One factor contributing to reduced pavement lives involves the number of heavy trucks and buses supported by a single rear .axle rather than by a dual tandem system. This paper presents a comparative summary of typical vehicles on our roadways and their 18-kip Equivalent Single Axle Load Factor. It also presents a summary of required pavement sections developed for major municipal roadways within the DFW Metroplex.