I have a 20 mile commute one way that requires me to drive 2 miles of it on dirt roads. They seem to grade them approximately every two weeks. The speed limit is 25. Most people I know seem to travel the road (as I do) at around 50mph. There are the few exceptions that travel it at 25mph religiously. I prefer to skim the top of the washboard vs. getting the fillings knocked out of my teeth at 25.
Dopers, I’m sure some of you have to deal with this phenomenon at times. My little car obviously performs and handles better at speed than my truck, which weighs 2.5x the weight of the car.
So - dirt roads. Fast, or slow?
Mythbusters did a program about bumpy roads, I think… can’t remember the outcome though. As long as there are no sharp corners, I say take any road at high speed. Plus, you can sometimes get a really huge plume of dust going. That’s got to irritate other drivers, but it’s sorta satisfying.
Speaking as the safety manager for an oilfield service company that operates vehicles over many unpaved roads, I can’t emphasize enough: go slower than you think you have to. Your vehicle has much less traction on an unpaved surface. If you come to an unexpected obstacle, such as an animal entering the road, you’ll have much less of chance of avoiding it, or of ending up in the ditch if you do avoid it.
It’s a common habit to drive unpaved roads at speeds far in excess of safety, due to low traffic levels and the assumption that you can see all hazards well in advance.
Other issues that increase risk include the rooster tail of dust and the possibility of throwing windshield-breaking stones. Sorry about the washboard effect, I know it’s annoying. 50 MPH on such a road, though, under many conditions, may be unsafe.