  Road corrugation refers to the formation of periodic, transverse ripples on
unpaved road surfaces. It forms spontaneously on an initially flat surface
under heavy traffic and can be considered to be a type of unstable growth
phenomenon, possibly caused by the local volume contraction of the underlying
soil due to a moving vehicle's weight. In the present work, we demonstrate a
possible mechanism for road corrugation using experimental data of soil
consolidation and numerical simulations. The results indicate that the vertical
oscillation of moving vehicles, which is excited by the initial irregularities
of the surface, plays a key role in the development of corrugation.
