Back roads in Australia often have hundreds of metres of gravel corrugations, or ridges. They are always a few centimetres high, spaced about 30 centimetres apart… and annoying for vehicle occupants. What causes them?
Tony Blake
Glenalta, South Australia
We pay £25 for every answer published in New Scientist. To answer this question – or ask a new one – email lastword@newscientist.com.
Questions should be scientific enquiries about everyday phenomena, and both questions and answers should be concise. We reserve the right to edit items for clarity and style. Please include a postal address, daytime telephone number and email…
