Development of Roughness Thresholds for Preventive Maintenance Action Aimed at Reducing Dynamic Loads

Abstract

In this discussion, roughness threshold values and corresponding life extensions are determined using relative damage and reduction in pavement life concepts. Using the fourth power law the following were calculated and plotted for 333 sections: relative damages from the 95th percentile dynamic load at different roughness index values and the corresponding percent reduction in life. A newly developed roughness index, the dynamic load index (DLI), was used for this purpose. Estimates of pavement life extension resulting from smoothing its surface were then generated for different remaining service life (RSL) values. The results were presented in tables showing the expected life extension for a range of RSL and DLI values. These tables would enable a highway agency to determine when a particular pavement needs to be smoothed to obtain a given (desired) life extension. The analysis was done for the three pavement types (rigid, flexible, and composite). RSL values were calculated for 805-m (0.5-mi) sections using actual distress growth over time. The results showed that for rigid pavements, 17% to 51% of sections would have life extensions of more than 3 years depending on roughness level. For composite pavements, none of the sections would have life extensions of 3 years or more. For flexible pavements, 9% to 34% of sections would have life extensions of more than 3 years depending on roughness level. These results indicate that preventive maintenance by smoothing action is best suited for rigid pavements.