Originally posted on the member side. This is an important topic that I feel most flatland and eastern non-professional drivers could use some additional information on. It was done in response to another member's questions about a trip that he took to Yellowstone Park.
If you or your wife are uncomfortable with steep grades and huge dropoffs maybe you had better stay off of Beartooth or Dead Indian passes. Dead Indian Pass is over 1,000 ft elevation lower than Beartooth, yet still involves the descent of a 3,000 vertical foot near cliff on the west side of the pass on a narrow 2-lane road. Next time that you are heading to Steamboat Springs, just remember that the same thing is true on Rabbit Ears Pass too. On Rabbit Ears, (which is 3 lanes wide), the first curve is 90 degrees to the left, and the 2nd is a 180 degree horseshoe to the right. And at that point, you will be almost 3,500 vertical feet above the valley below. It is kind of like several minutes away from landing in a jetliner, except you are in your car and a profesional is not doing the driving. The number one thing to remember if you are trying that is to keep your eyes on the road and let your passengers look at the scenery. You want to see the scenery somewhere, pull over and park. Right behind the Cliffhanger Restaurant on CA. Route 18 there is a really nice 5,000 ft vertical dropoff, but you have to park to see it. But whatever you do, do not ignore the No Parking signs and park on the upper horseshoe on the west side of Wolf Creek Pass.
I will try to make the complex issue of semi mountain braking and climbing performance as simple as possible.
Right off the bat, on a flat, no-gradient road, it takes a loaded semi 3 to 4 times as long to stop as your car can stop in from the same speed. On steep mountain downgrades, that figure can easily increase to 5 to 8 times as long or longer, depending how hot the truck's old-style drum brakes are. Unfortunately, not every truck driver has extensive experience operating over high altitude mountain passes, and it seems like most highway engineers are rather ignorant of the special needs imposed by large trucks. So there are some things that you need to be aware of driving over large mountains.
When you descend steep mountain grades in your car, your engine back-pressure is enough to hold you back most of the time, and sometimes has to be combined with light to moderate braking, especially coming into sharp curves. What most people don't know is that on an engine size to vehicle weight ratio or a horsepower to vehicle weight ratio, your car's engine is 5 to 8 times as large as a semi's engine is. (The 4.7 liter/275 cu in V-8 in my Dakota pickup is 1/3rd the size of my semi's 14-liter engine, but my pickup is 1/16th the legal gross weight of my big truck. My pickup's rated horsepower is over half of the 500 horsepower of my semi's engine, or over 8 times as powerful). It is no wonder that we have a fuel crisis.
Heavy truck's engine brakes are of two different designs. The first is less-expensive and more widely used. It is an engine compression brake where the fuel flow is cut-off to up to several cylinders. A lot of communities have become rather sensitive to the noise which was worse years ago or is still worse at certain engine manufacturers. That is why you see those signs. The other less-widely used engine brake is a hydrualic retarder which mounts over the driveline. There is virtually no noise with this type, but excessive use can overheat the truck's engine or transmission oil, depending on how it is hooked-up.
On long steep mountain downgrades especially toward the bottom car drivers must be aware of the possibility of out-of-control semis with their brakes on fire, and be ready to take evasive action if necessary. Always check your mirror and make sure that trucks are not gaining on you really fast when descending steep downgrades. In the case of Beartooth or Dead Indian passes the problems with mountain truck braking should not be as much of a problem as on many other high passes, because most trucks are not allowed in Yellowstone Park. But over time I have seen a number of cars towing campers or heavy boats, or large 5th-wheel rigs lose their brakes due to inexperience too. One time I saw a 5th-wheel camper pull right off of I-70 into a gas station in Georgetown with the brakes on fire. I'm still surprised that the gas station is still there!!!
Anyhow, back to Wolf Creek Pass westbound on US 160, which is basically the most major heavy truck access route to Durango, CO from the east. The upper part of the westbound hill is over 5 miles of 8% grade, which is comparable in gradient but twice as long as Floyd Hill westbound on I-70 is, and steeper in gradient than the westbound side of the Eisenhower Tunnel on I-70. There are two runaway ramps, the last of which is over a mile before the upper horseshoe. Oh yes, from the upper horseshoe there is a stunning view off the top of a nearly 2,000 ft vertical cliff. All summer long there will be a line of unknowing cars and campers parked there playing Russian roulette. If you look close at the rock wall you will notice a number of places where the rockwork seems to be newer than other places. Those places are where some luckless semi driver wasn't able to negotiate the 30 mph left curve, and went flying into outer space for the 15-second free-fall into the trees. And if there is a line of parked cars and campers in the way, someone is going to have to go with him too.
Back to the flashers. Even with 500 horsepower and my foot to the floor, as I climb the grade, the truck keeps slowing down. Several States like Pennsylvania have laws about climbing vehicles below certain speeds and generously post that information on highway signs. Other States have laws but don't post it as much, and still others don't have laws regarding slow vehicles and use of the flashers. Generally when you see their flashers on it means that they are operating below 40 mph, or, they are trying to back up. I am continuously surprised how many people still don't know that.
Now you know a lot more about it, and I feel that you are now ready for another mountain vacation. Just remember what I said: Keep your eyes on the road. And don't be afraid to pull over and let those in a bigger hurry pass. There is nothing like the stress of a line of closely-following traffic to make people do things that they are uncomfortable doing.
I posted this publicly because I wanted as many people as possible to have this knowledge.
Just a few pointers from a 4 million mile professional.
PS: My dad was at one time a race car driver and a tank commander, and he used to love to frighten the women in the mountains, so that doesn't seem to be that uncommon either. I remember taking my wife's flatland sister up Oh My God Road (between Idaho Springs, CO and Central City, CO), which is a single-lane dirt affair without guardrails that climbs close to 3,000 vertical feet). Just in the first 3/4ths of the way up, she screamed Oh My God!!! almost 20 times, which was met with mocking derision from the front seat occupants. It just so reminded me of when my mother's step-dad did it to her and my grandmother back in the 1960s. So a little high-altitude ribbing is a time-honored tradition in my family.
"We stay here, we die here. We've got to keep moving". Trucker Mark