Washboard effect on paved roads?

I read the article What causes the “washboard” effect on unpaved roads?, but here in Greece many paved roads have the washboard effect as well. These roads have almost always heavy truck traffic and the effect is more pronounced before intersections.
What causes this effect?

I’ve seen it on asphalt paved roads at intersections near construction sites where fully loaded dump trucks have to brake for a stop light. It looks like the road surface is being stretched and deformed by the force of the braking trucks.

I have seen it a lot at stop lights here in the Netherlands. My WAG is that the top asphalt coating actually behaves like a higly viscous liquid when the weather is warm and sunny. If a heavy truck is stopped at the light, it will actually push back on the asphalt the moment it begins to accelerate, causing “wrinkles”.

Like I said this is just a WAG. I’ll see if I can find anything more specific on Google.

Well, I found one document (in Dutch) here that seems to support my claim. However, it says that braking actually causes much more deformation than accelerating (which sounds logical and correct now that I think about it). Think of a running person suddenly stopping on a rug. It also says that the washboard effect is increased by cars then stopping in the “dips” or “valleys” when they are at the trafiic light.

Since your question is pretty much tied into the effect discussed in the Staff report, let’s put this in Comments on Staff Reports.

samclem GQ moderator

“Washboarding” is almost always more pronounced in areas where vehicles are braking or accelerating. Since top braking force is usually greater than best acceleration, it would follow that washboarding would be greatest in areas where strong braking takes place.

I’ve commuted on Interstates for many years. One “Off Ramp” I usually took was totally ridged. The County fixes it once a year, but I think they like to keep the bumps to slow down the trucks

It’s a big problem on roads and junctions near truck depots. It is indeed the rebound of the truck suspension that causes the dips, and it will do it in just about any road surface that isn’t solid concrete.

The distance between the dips is a linear function of the damped frequency of oscillation of the offending truck’s suspension, and the offending truck’s speed. Other vehicles may have suspension with different boing rates and approach speeds, but the positive feedback principle that Cecil mentions does incline vehicles to match their speeds to coincide with minimum ripple-bounce, which only adds to the road destruction.

It’s not just braking zones that are vulnerable to such rippling either. Anything that makes the suspension bounce, such as a pothole or speed hump, will give rise to an adjacent washboard.

I’m not sure that the rippling the OP talks about is the same phenomenon as washboarding. I’ve seen rippling like that, but the ripples are usually spaced a few feet apart. Washboarding, though, has ridges spaced an inch or a few inches apart.

Fair point Chronos, I wasn’t aware of the distinction. I was talking about bumps a foot or two apart. I imagine smaller ripples are caused by the slightly fluid road surface being rucked by braking front tyres (imagine braking on a rug), and the reponse of the tyre itself under braking deformation will have an influence on the pitch of the ripples. The suspension itself won’t have an effect on the smaller ripples, unless it’s to modulate longer-pitched peaks and troughs into the overall effect.