A truck driver can drive down a mountain 100 times too slowly, but only once too fast. An inexperienced driver on a steep grade could spell disaster unless properly trained.

In April 2019, a horrific truck crash occurred on Interstate 70 near Denver, Colorado. An apparently out-of-control truck careened down a 5-mile stretch of steep highway grade before slamming into a line of stopped traffic. Four people died in the ensuing inferno; a dozen others were seriously injured.

The speed limit for trucks on that hill is posted at 45 mph, yet witnesses have video showing the truck scorching past a runaway-truck ramp at well over 60 mph.

The investigation into the crash is ongoing as of this writing, but the driver's level of experience has already been called into question. Published reports indicate the driver, 23-year-old Rogel Lazaro Aguilera-Mederos, of Houston, Texas, has had a commercial driver's license for less than three years and had only recently begun operating outside his home state. 

There's no indication of how much mountain driving experience he had, but it's safe to say he didn't get any mountain training when he took his CDL course in Houston.

The Texas CDL training manual (and most others for that matter) has only 1.5 pages devoted to mountain driving, which is little more than a footnote to the full training curriculum. That's probably not much different from what many CDL trainees get.

When Driver Training Doesn't Prepare Truckers for Driving in the Mountains

There are few areas in the country that have hills, never mind mountains, big enough to train on. So many newly minted commercial drivers find themselves in places like Colorado and Western Pennsylvania and Washington without a thorough understanding of how to manage long downhill grades in heavy trucks.

"Far too many commercial drivers today 'bet the house' while descending steep grades," says Larry Hall, a veteran British Columbia-based owner-operator and organizer of a group calling itself ADEPT (Assembly of Drivers, Educators and Professional Truckers) that is trying to raise entry-level driving course standards across Canada. 

"Equipment today provides a false sense of security. With upwards of 600 horsepower of engine-braking ability, there seems to be little or no concern for the 'what if' scenario: What if the engine brake fails? What if you come around a corner and traffic is stopped or there is an animal standing in the lane? Those drivers have no Plan B."

Entry-level driver training is a hot topic today, with the Federal Motor Carrier Safety Administration moving to establish training programs that adequately prepare new drivers for the real world. While most agree that it's a step in the right direction, entry-level training is just that. Mountain driving, like winter driving, is an advanced driving skill.

How do Flatlanders Teach Mountain Driving?

Karl's Transport of Antigo, Wisconsin, recently opened a training facility of its own to help get new drivers into the company ranks. It offers instruction to any prospective driver, but applicants are offered free tuition if they agree to work for the company for at least 18 months after obtaining their CDL. 

Tim Kordula, the school's chief CDL instructor and administrator, says the program lasts between eight and 10 weeks, depending on the progress of the students. He spends at least one full day discussing what he calls extreme driving, such as mountains, winter weather, and road construction.

"We don't have much in the way of mountains in northern Wisconsin, but since we run 48 states and Canada, our drivers need to know about mountains and weather and those more challenging parts of the job," he says.

 "We can't replicate the Colorado front range, but we do have a couple of hills near here with a 5% grade that we spend a day practicing on. I think that gives our students at least a sense of what the mountains are all about."

Kordula takes the students up and down those hills, practicing shifting and braking techniques as well as procedures at brake-check areas, still found at the top of many mountain grades.

"We cover brake inspection and adjustment, air compressor performance and why we use snub braking; that sort of thing," he says. "We talk about brake fade and runaway ramps, too. That's usually an eye-opener for the students."

The Challenge of Geography

Beyond whether advanced driving skills can or should be taught in an entry-level program, there's the problem of geography. You can't do much more than lecture on mountain driving in many parts of the U.S., as the requisite terrain simply doesn't exist.

Andy Roberts owns and operates a driving school called Mountain Transport Institute in Castlegar, British Columbia, in the Kootenay Mountain range in the southeastern part of the province. It's quite literally surrounded by mountains.

MTI offers tractor-trailer driving instruction on several levels, from a five-week entry-level to an eight-week advanced course. It also offers a week-long mountain driving program that includes four hours of classroom instruction, two hours of shifting-simulator training, and 24 hours of in-truck instruction on the four mountain passes located near the school.

Perhaps surprisingly, even British Columbia does not include any formalized mountain driving training in its existing CDL training or testing. Roberts says the B.C. driver's handbook includes a couple of pages of decent information on the topic, but drivers aren't necessarily tested on the material, and there's no mountain component to the driving test.

"My entry-level program includes at least one trip down a mountain grade, and my advanced students get two days out there," Roberts says. "It's not ideal, but at least the entry-level driver gets some exposure to the driving techniques required to drive safely in the mountains."

Into the Unknown

Drivers exposed to mountains for the first time face a dilemma. They don't know what lies ahead and therefore won't be aware of what speed they should be traveling. Some grades have signs that display a profile of the hill; some signage offers ambiguous warnings such as, "Use Lower Gear" or "Slow Down" – but lower than what? How slow?

During the development phase of a tablet-based in-cab application designed to provide drivers guidance and warnings about the proper speeds to use on slopes and curves, research revealed that even experienced drivers consistently drive as much as 20 mph over what would be considered a safe descent speed on the mountain roads on which they were testing the app.

"In about half of the slope runs we observed, drivers reduced their speed by using brake snubbing to slow the truck, but they still did not get down to the recommended safe descent speed," says Garth Lawrence, one of the developers of the Road-Aware app.

"Many times, we saw drivers running 20 mph or more over the recommended safe descent speed, driving right past a runaway truck ramp that the Arizona DOT says is used about twice a week by runaway trucks."

Lawrence's observations produced some interesting insights into driver behavior when braking on long slopes. They understand the need to reduce speed, but they seem to be operating under a false sense of security. They underuse their engine brakes and snub or drag the service brake to check speed increases. This inevitably increases brake temperature, which reduces the brakes' stopping power – known as brake fade. 

Like the 100 times the driver may have descended that hill previously, they are still under control and still have some service braking capability left, even though it may be seriously diminished. But if on the 101st time down the hill an animal steps onto the road or they run into stopped traffic, the ability to stop is jeopardized.

The problem, Lawrence says, is that drivers are not using the safest method for descending hills. It's not a matter of driving at a given speed; drivers should be descending at a speed that allows them to use only the engine brake – no service brake applications at all.

Safe Mountain Descent Technique

That's the way Roberts instructs his students. He says drivers should not need to use the service brakes at all to slow the truck if they are driving at the appropriate speed. The engine brake provides the most retarding power at higher rpm, so keep the engine speed in the 1,800- to 2,000-rpm range. If this slows the truck too much, do not upshift; instead, switch the engine brake to position 1 or 2.

"If you need a service brake application to check the speed, you're in too high a gear," he says. "Conversely, if you are running the engine brake at 1,500 to 1,600 rpm on position 3, you're in too low a gear. 

"The steepness of the grade will vary, so toggle the engine brake between the three positions to maintain a safe, steady speed. Use position 3 on the steeper portions, and toggle back to position 2 or 1 on the less-steep portions of the hill. If you're in the right gear, you should not need to apply the service brakes to slow the truck."

In recent years, much emphasis has been placed on keeping engine rpm as low as possible to conserve fuel, which means 1,800-2,000 rpm may seem like forbidden territory to some drivers. You are not using any fuel when using the engine brake (no more than you would at idle). 

With the engine brake on, the engine acts like a big air compressor driven by the truck's momentum through the drive wheels. Teach drivers they can keep the engine speed high, and understand that fuel economy will not suffer.

Some automated transmissions are programmed to upshift automatically when engine speed reaches a certain point. While running the engine at 1,800-2,000 rpm, drivers may need to place the transmission in "manual" or "hold" mode to prevent an upshift. If they are going too fast to begin with, even at high rpm, the weight and speed of the truck coupled with the steepness of the grade may eventually cause the transmission to upshift to protect the engine from overspeed. 

The problem there is not an inadequate engine brake; it's that the truck is going too fast for the engine brake to maintain a safe speed.

"If you get into the wrong gear, the time to fix that is at the top of the hill before the brakes get too hot," adds Roberts.

The old bit of wisdom drivers once used, "use the same gear to come down the hill that you used when climbing the hill," doesn't always apply today.

"Engines are more powerful than they once were and may be capable of climbing faster than they can safely be driven down the hill," Roberts says. "Besides, you may have a different load on coming down than when you went up the hill, or you may have never been on that hill before."

The best course of action is still to choose a gear that will allow the truck to maintain a speed where the engine rpm is in the 1,800- to 2,000-rpm range in any of the three engine brake positions, depending on the steepness of the grade.

What About Disc Brakes?

All the technical detail we have discussed here, so far, relates to drum brakes. Drum brakes are subject to brake fade because excessive heat can change the friction properties of the lining and the drum expands as it gets hotter, causing increased stroke length and eventually diminished application force.

Disc brakes are fundamentally different: the rotor, which rotates between two brake pads, expands toward the friction material as it gets hotter, shortening the application stroke and improving brake performance.

If the tractor has discs and the trailer has drums, or vice versa, an imbalance situation could result where the disc-equipped vehicle is doing more of the work, causing those brakes to wear faster.

However, even with disc brakes, the weight and speed considerations still apply. A loaded truck barreling down a hill will need a much greater distance to stop than when operating on level ground.

If you stick with Andy Roberts' advice on how to descend a mountain grade, it won't matter if you have discs or drums because you won't be using any service brakes on the hill anyway, right?