Mountain Driving Challenges Part 2 Unique Hazards

June 17, 2010

Last week’s Lug_Nut tip, we looked at managing speed while descending steep grades in mountainous areas. Now let’s look at some of the other hazards that you might encounter when operating in high elevations and mountainous terrain.

Road Surface Ice Patches: Temperatures drop as elevation increases at a rate of about 3.56 degrees F. per thousand feet. This is known as the “normal lapse rate”, or temperature to altitude ratio. While this is the usual ratio it can vary. A steeper lapse rate can be experienced when the weather becomes unstable and the ratio may exceed 5 or more degrees F. for every one thousand feet of elevation. Likewise another phenomena is possible where the lapse rate is very low, nil or even a slight increase may be found. This may be an inversion, where warmer air is forced aloft. But never the less, you are far more likely to encounter a normal lapse rate, hence the word “normal”. So, on a 50 F., day driving over a 5,000 ft. mountain pass, freezing temperatures are quite probable. This can result in icy conditions if precipitation is present. But, even on a sunny day ice can form from water running down from the mountains above, particularly in shaded areas.

Wildlife on the Road: While many lower elevation roads present this problem, many mountain roadways have an additional animal, the mountain goat that often wanders on the highway. Rugged terrain can also make the road edge an appealing passage in some circumstances which may result in an increase of roadway wildlife traffic. Combine this with the twisty roads and poor forward roadway view, a shorter warning of wildlife is to be expected.

Rock Fall Warning: While a rock slide is highly unlikely, the possibility of encountering some small rock pieces on the roadway can be very real, particularly after a heavy rain fall. Generally these rock fragments are jagged and can damage or destroy a tire or vehicle. Reducing speed when such warning signs are posted can increase your maneuvering and stopping ability. We have all seen the yellow warning signs, but it is surprising how little attention they are given by most drivers.

Precipitation on an Otherwise Clear Day: When operating at higher altitudes in mountain ranges that are snow capped, precipitation can be encountered even on what looks like a clear day. This can happen when humid air drifts across the snow caps. The frozen ice and snow reduces the air temperature to, or below, the dew point. At this temperature some cloud formation will appear and snow or fine rain may fall.

Reduced Visibility Possible: Quite often the clouds are lower than the mountains are high. If the roadway rises up to, and through, the cloud base, vision may be reduced to near zero. Slow down and observe caution as you would driving in fog.

Shear Road Edges: Unlike most roadways found in the lowlands, mountain roads occasionally have no shoulders or guardrails in some sections. These require special care and attention. Wondering off the road in these areas can have disastrous results.

Engine or Transmission Overheat: Climbing steep grades takes horse power and torque, this causes the drivetrain to heat up. To keep your engine and tranny running cooler, climb grades in a manually selected gear. This then will allow partial throttle climbs without the automatic up-shift. Operating your engine at higher RPM will allow the cooling package to run more efficiently during hard pulls.

Fuel and Services: Generally you don’t see fuel and service stations in the mountains. So, make sure you have ample fuel and that your fluid levels are all topped up.

Affects of High Altitude: Generally there is little affect to most people when exposed to 5,000 feet or so. But there are far higher elevations in the U.S. that you can drive to, about 12,000 feet or more. If you are planning a trip that may take you to these extreme elevations, it would be wise to look into altitude health affects for yourself and those travelling with you. If you plan to camp in the mountains you should be aware of the reduced output that your generator can supply. For each 1,000 feet of elevation above sea level, a 3.5% drop in output will be experienced. So, for example, if you have a 7,000 watt unit, you will only have about 5,500 watts at 6,000 feet or 4,500 watts at 10,000.

Well, those are just some of the challenges you may face when travelling through mountainous regions. The geographic beauty, however, is well worth it. If you have never ventured on these roads in the sky, you may want to give it a try. Just drive safe.

With Some Hazardous Thoughts – Lug_Nut – Peter Mercer