An overview looks at issues affecting forecasting of traffic loads for pavement design with the Mechanistic–Empirical Pavement Design Guide methodology. The establishment of reliable observed traffic data has recently received considerable attention. However, relatively little attention has been paid to the necessary task of projecting observed historical traffic data to future years. The three hierarchical data input levels of the design guide apply not only to the observed traffic data but also to the forecasting of traffic data throughout the pavement design period. The forecasting effort should be commensurate with the hierarchical input levels. The topics related to forecasting of traffic loads for pavement design include forecasting of truck volumes, changes in truck types, and axle load spectra; the use of axle load spectra in the forecasting process; and the estimation of maximum traffic volumes that highways can carry. The main trends affecting future traffic loads include economic conditions, restructuring of the economy and manufacturing industries, globalization of the economy and the effect of free trade, regulatory changes in truck size and weight, changes in cargo shipping, e-commerce, and improvements in truck utilization.