Review of published research into the formation of corrugations on unpaved roads.

The report reviews published information on the problem of the formation of corrugations on unsurfaced roads. Early theories, which were reviewed by the Laboratory in 1958, are contrasted with more recent work. There is now wide acceptance for the theory that corrugations are formed by forced oscillations at the resonant frequency of vehicles' suspension and tyre systems. There is, however, no clear understanding of why certain road materials corrugate whilst others do not. (Author/publisher)