Why do dirt roads end up with hard ripples?

Question

Why do dirt roads end up with hard ripples?

In: 17

Answer 1

> [According to the Federal Highway Administration (FHWA), the four primary causes of washboarding are driving habits, lack of moisture, poor gravel quality, and lack of crown on the road surface.](https://blog.midwestind.com/how-gravel-roads-get-washboarding/)