Published in 2009
The Virginia Department of Transportation's (VDOT's) current pavement design procedure is based on the 1993 AASHTO Guide for Design of Pavement Structures. In this procedure, a required structural capacity is calculated as a function of the anticipated service life, the serviceability of the pavement, and the number of equivalent loads applied. The concept of equivalent applied loads allows for the pavement designer to account for the damage caused by loads of varying magnitudes and axle configurations. Although pavement damage can be expressed per axle, expressing the damage in terms of the average amount of damage caused by a particular vehicle is more convenient. This is referred to as a truck factor, which is the average number of equivalent single-axle load (ESAL) applications per vehicle. VDOT's current pavement design procedure subdivides truck traffic into two categories, i.e., single-unit trucks and combination trucks, and was based on studies performed in the early 1990s. Over the last few years, VDOT has installed weigh-in-motion (WIM) devices at 15 locations around the state that measure the loads actually applied by vehicles in the travel lanes. These WIM stations allow for continuous data collection that was previously not available and therefore can provide a better representation of actual traffic loading. This study developed updated truck ESAL factors based on WIM data from June 2007 through May 2008 in Virginia. These factors were found to be 0.46 for single-unit trucks and 1.05 for combination trucks using flexible pavements and 0.59 for single-unit trucks and 1.59 for combination trucks using rigid pavements. The updated truck ESAL factors determined in this study should be incorporated into VDOT's pavement design procedure. Using the updated truck ESAL factors recommended in this study will allow a more optimal pavement design that more accurately reflects the traffic loading on roadways in Virginia.
Bryan C. Smith
Last updated: November 20, 2023