Washboarding

Washboarding occurs in dry, granular road material[2] with repeated traffic, traveling at speeds above 8.0 kilometres per hour (5 mph).

[6] Highway department experts in the mid-1920s were aware that traffic volume and speed were primary causes of corrugations on gravel roads and cited the role of drive wheels tossing material as a factor.

[7][8] Laboratory-scale studies of the phenomenon typically employ a wheel or a blade, which is towed behind a pivot point, tracing a circular path through a pan of the material under examination.

They also show that a passive, non-driving wheel suffices to create corrugations and that displacement of material, rather than ejection, is the dominant mechanism.

[11] The maintenance advice from Colorado was to drag or grade the road frequently, applying light volumes of new gravel with minimal sand content and providing good drainage with a crown.

Alternately, one can incorporate reclaimed asphalt in a half-and-half blend with quarried gravel to improve the binding properties of the surface.