Leaving Hilo I turn towards the shortest path home. It is also my favorite path by far. Not for me the twisting turns, small towns, and driving rains of the Hamakua coast road. I turn towards Saddle Road, to the pass between the enormous volcanoes of Hawaii.
The road is smooth and fast now. The Saddle of legend and rental car prohibition is mostly gone, only fragments remain. While you can still drive bits of the old Saddle, they are no longer the main road, bypassed by the new highway.
Even before the road was re-built this was my favorite route to cross the island. The traffic is far heavier now, the new road no longer offers the challenges and dangers of the old road. Drivers no longer deterred by those dangers now use the new road to cross the island rather than driving around the northern belt road.
It has long been policy on the Mauna Kea summit road to use four wheel drive while ascending the mountain. One of the reasons given is to slow the formation of washboard, the annoying ripples that inevitably form on gravel roads.
On Mauna Kea an oft cited mantra is that the use of four wheel drive when ascending the mountain reduces the formation of washboard. I have always suspected this is a mountain myth with no substance. Where does this belief come from? Is there any real information on this?
There are a great many references that detail the practical details of maintaining gravel roads. Generations of highway engineers have spent a lot of time studying and writing about how to best maintain gravel roads at the least cost.
The US Department of Transportation highway Administration has published a lengthy guide to the problems and solutions of gravel roads. This guide dedicates a dozen pages to the issue of corrugation or washboarding. While multiple factors in the formation and prevention of washboarding are discussed there is no mention of 4WD vehicles being a factor.
Headed for work, at least I had plenty of time… Ahead of me on the hillside I could see a military convoy with dozens of cars trapped behind them on the steep grades. Not wanting to join the mess I pulled over to take some photos. The convoy will turn towards the new Saddle Road at the top, all I have to do is give them another five minutes and I will have open road.
Rush hour for Mauna Kea is just before sunset. This is when the day crews are coming down, while the summit tours and telescope operators are heading up.
The timing of this rush can be variable depending on time of year and what time sunset occurs. Twice a year this rush is at its worst, when everyone heads up and down at the same time. This can lead to some difficult driving conditions… A lot of vehicles on a road that can be challenging. A cloud of fine cinder dust and a setting Sun just adding to the confusion…