Washboard roads

Anytime you get off the pavement onto a well traveled and maintained dirt or gravel road, you will probably encounter the dreaded washboard surface. It’ll rattle your teeth. A roll of toilet paper on a shelf above the bed in the RV was vibrated round and round making a nice stack of paper on the bed below during the short off pavement trek to Obsidian Dome. A nice long stretch of severe washboard is that stretch of road from Dayton to Fort Churchill along the Carson River by the test facility. These are often known as ‘Nevada Highways’ as much of Nevada is only accessible via dirt road.

Some say it is due to a bad road foundation – not having the right depth and kind of rock and soil under the road surface. Others think it is due to a lot of traffic and frequent maintenance. Science News Online reports on a study by Stephen W. Morris of the University of Toronto and his colleagues Nicolas Taberlet and Jim N. McElwaine of the University of Cambridge in England to find out why washboard roads form by using simple experiment.

One way to avoid washboard roads is to limit traffic to walking speeds. This is why those roads suffering lack of maintenance often don’t show the phenomena. It is difficult to travel at more than a walking speed when driving over potholes and boulders.

But when there is traffic, there is a demand for maintenance. Potholes are filled in and boulders removed. The road is scraped smooth. Traffic speeds up to jogging speed or faster, and the washboard forms.

Any bed of dirt or sand, even a very smooth one, has minuscule irregularities that slightly jog a rolling wheel. Each time the wheel hits a bump, the computer simulation showed, it pushes the dirt forward a bit, enlarging the irregularity. Then, as the wheel passes over the top of the bump, the force of its descent pushes dirt forward into the next bump. Repeat these actions a hundred or more times and the familiar pattern of ridges appears.

It has little to do with substrate. It has little to do with maintenance – that is correlation and not causation. What it does have to do with is the fact that it is a dirt road and the dirt, rock, or sand on the surface is easily moved as tires roll over it. Once those tires get to moving fast enough to push the material to a berm in front that it has to bounce over, washboard will form.

Modern highway vehicles are not designed to go slow enough to avoid washboard formation. You need deep gears to be able to idle along that slow. The difference between 5 and 15 mph isn’t much from the driver’s seat but can make a significant difference in time on a 5 mile driveway to a campground. Once the washboard forms, even walking speed isn’t slow enough to keep from getting rattled.

Think Independence Lake off CA 89 versus Obsidian Dome. At least up to the visitor area, the Obsidian Dome road is well maintained and has enough washboard to unroll the toilet paper. You can drive an RV there without worrying about bottoming out or getting stuck on a grade. Independence Lake is another matter. To get there you have to crawl over boulders and cross streams and worry about ripping off the back bumper (as Roger did on one backroads jaunt) or scraping the hitch.

Washboards are a fact of life on unpaved roads. Those are the roads that will get you to some of the more out of the way camping spots. There isn’t much you can do about it except make sure everything is tied down (e.g. a rubber band around the toilet paper), take it easy, and check all the nuts, bolts, screws, and rivets to make sure they are tight for the next trip.

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