Observation of a series of full-scale road experiments in the United Kingdom indicates that, after an initial period of deformation, reflecting compaction, and moisture changes, permanent deformation and rutting can be related to ranges of cumulative equivalent standard axles of 82 kN (18,000 lb). Cracking of structural significance seldom occurs until ruts have developed to a depth of 10 mm (0.4 in.). After the cracking occurs, deformation behavior is more difficult to predict; continuity of the relation of the cumulative equivalent standard axles is most likely on stronger pavements. The marked influence of temperatures and subgrade strength on deformation is demonstrated by results from the AASHTO Road Test in the United States and from road experiments in the United Kingdom. Essentially similar behavior was observed in both countries, and differences can be related to differences in climatic conditions. Accelerated pilot-scale testing under controlled conditions of wheel load and temperature in a circular road machine has quantified the contributions of these two factors to deformation behavior. The link demonstrated between this type of testing and actual road behavior indicates its potential for developing and validating predictive models of deformation behavior.