06/23/09 Bend
 
In this ‘You Ask, We Answer' Shaun asks, "I am curious to know why on many of the dirt roads and forest roads in Central Oregon why a type of washboard effect is present.  It's like driving over a million little speed bumps!  Why does this happen?"
 
 
Experts say it's inevitable unless the roads are frequently scraped by bulldozers.  Speed plays a key role in the bumps developing.  According to a study done in 2007 by researchers at the University of Toronto and the University of Cambridge in England, each time the car wheel hits a bump, it pushes the dirt forward, enlarging the irregularity.  As the wheel passes over the top of the bump, the force of its descent pushes dirt forward into the next bump.  Repeat that hundreds of times and the washboard effect appears. 
 
Some experts say driving under five miles an hour will help slow down the creation of the bumps.