VAA Virginia Asphalt Fall/Winter 2020

28 FALL/WINTER 2020 PERPETUAL PAVEMENTS The Next Evolutionary Step The evolution of flexible pavement thickness design began with experience- based approaches before the 1950s through empir- ical methodologies first created in the 1960s based on full-scale road tests. These empirical methods, most notably the AASHTO series of empirical design guides, have reigned supreme in the U.S. over the past 50 years with the vast majority of paved mileage designed, constructed, and rehabilitated according to their design equations. More recently, pavement design has evolved into mechanistic-empirical (M-E) approaches with AASHTO now using the Mechanistic-Empirical Pavement Design Guide (MEPDG) and accompanying software, AASHTOWareTM Pavement ME Design, as their standard approach. Many states are transitioning into using M-E design. Still, the process can sometimes advance slowly due to the need to evaluate, calibrate, and validate the new M-E approach before taking the next evolution- ary step. Regardless of the approach, pavement design has always attempted to predict distress development as a function of time and traffic application. Using equations Frequency Washington 4 Oregon 0 California 2 Nevada 0 Utah 0 Wyoming 0 North Dakota 1 South Dakota 0 Nebraska 4 Kansas 0 Oklahoma 4 Arkansas 10 Tennessee 15 North Carolina 0 Missouri 3 Iowa 2 Minnesota 16 Wisconsin 1 Michigan 3 Illinois 1 Indiana 1 Ohio 4 Pennsylvania 9 NewYork 0 Maine 0 0 0 Kentucky 4 Virginia 1 Georgia 0 Florida 10 South Carolina 8 West Virginia 0 Texas 2 Louisiana 0 Alabama 11 Mississippi 4 Colorado 3 Arizona 1 Alaska 1 New Mexico 0 Idaho 0 Montana 5 Powered by Bing ©GeoNames, Microsoft, TomTom 0 16 FIGURE 1: Perpetual Pavement Awards Through 2019. Dr. David Timm, P.E., Brasfield & Gorrie Professor and Associate Chair, Department of Civil & Environmental Engineering, Auburn University