The article does talk about washboard roads, but it DOESN’T answer my question. I understand that car tires force the gavel, rocks, etc. around on a road’s surface, but why do they align in rows like waves? And do those ‘waves’ connect across roadways even in areas where tires don’t usually pass?
[q]Bumps in the road surface cause the tire to hop in the air. When the tire crashes down, it forms
valleys by spraying sand and gravel forward and sideways. The moving tire ramps out of the valley
and hops again. Thus, the washboarding process repeats itself.[/q]
Australia’s answer to Cecil Adams, Dr Karl Kruszelnicki has this to say about road corrugations (or “washboards”, as you 'merrikans call 'em). Come to think of it, he also had this to say, as well as this. Oh yes, and this.
To save you the trouble of wading through all those links I gave above, here is a theory regarding the appearance of corrugations across the entire width of the road (the part I have italicised… -the er… text, not the road ):
Some of it is also caused by the grader operator making a mistake and chattering the blade on down the road. I’m surprised the Alaskan link didn’t seem to mention this - it seems to be a regular feature up North. Or maybe it’s just our crews.
I got this off some of the guys who work highway maintenance in the Yukon.