Abstract
We consider a model of cars driving along a compressible or erodible road. Each car is modeled as a mass supported above a wheel by a damped spring. We find conditions under which a flat road surface is unstable and gives way to a regular pattern of corrugations. The instability is mitigated by the damping of the cars' springs and also by the tendency of the road surface to harden as it is compressed. Similar phenomena occur in railroad rails and in calendaring of paper.
