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Going Downhill Fast

Posted by Eric Roeder, Instructor, Driver Development on Nov 3, 2020 9:15:00 AM

In Corporate, Safety, Drivers, Business

You are a Bison Driver, heading into mountainous or hilly terrain. You may be looking forward to it as such areas offer up idyllic views and gorgeous vistas.

Unfortunately, a scenic drive through the mountains or hills also presents many risks and dangers. There are steep grades, twisty curves, roadside cliffs, drop-offs and rockfaces, often on roads with only two lanes of travel and little or no shoulder.

Traveling through these areas demands a high level of attention, as well as advanced driving knowledge and skills. Many Drivers rely only on their limited knowledge of downhill braking and often focus in on downhill brake management techniques.

Most Drivers know that long descents can be particularly dangerous. They know that brake performance begins to fade as the pads or shoes and rotors or drums become overheated, resulting in less friction between them, and more force will be needed to achieve the same level of braking. The most important thing they need to know, however, is that in the most extreme cases brake fade can cause complete failure of the brakes.

Snubbing or Not: Wrong!

In Driver Development discussions of this topic, differing techniques of downhill braking are often hotly debated. Some Drivers insist the best method to stay at a safe speed is to apply the service brakes as lightly as possible all the way down the grade. Others insist that the safer method is to allow the vehicle to coast for short periods, gaining speed, then “snub” the brakes (firmly brake for a short period of time). This technique allows more cooling time for the brakes in between applications.

Everyone wants to know what the experts advise (usually snubbing), and it is generally agreed that snubbing the brakes is the safer method as it helps to prevent dreaded brake fade.

Sometimes Drivers are lulled into a false sense of security by traversing over smaller grades or shorter hills that they can run at some speed and use their service brakes (either snubbing or light braking) without issue. Using this incorrect technique as they eventually reach longer and steeper grades presents significant risks.

Don’t Use Brakes At All

The often-missing bit of information that trumps all discussions (and is also advised by the experts) is simply that service brakes shouldn’t even be used to slow down while descending a hill. Brakes are only to stop the vehicle or slow it down for a downshift. They were never designed to hold the vehicle back when going down a grade.

In downhill incidents where a truck’s brakes have seized or caught fire or otherwise failed, it has usually been determined that the Driver simply descended the steep grade too fast and was forced to apply their brakes.

Service brakes need to be kept cool in the event a Driver comes across an emergency and needs to stop suddenly, like an accident, wildlife on the road, a rockslide, or even engine-brake failure, so they can apply the brakes to bring the truck to an abrupt stop.

Drivers may be wondering if they shouldn’t use their service brakes when going down grades, then how can they safely traverse that grade?

The Right Way Down

The answer is simple: Drivers must always slow down at the top of the grade and manually select the gear that will allow them to descend the grade safely using only the power of their engine and their engine brake (Jake brake). All Drivers must resist the urge to rely on their service brakes.

If the proper gear is chosen, the engine brake is used, and no or very little service brakes are used, and those brakes are properly adjusted, Drivers should never have any issues.

One good rule of thumb is to choose a gear or two lower than the gear used to go up the hill, that is if a Driver used 4th gear to traverse up the grade, then they should choose 2nd or 3rd to go down the grade.

Another rule of thumb to follow is that if the service brakes must be used, the Driver should be going slow enough that in addition to the properly selected gear and use of the engine brake (Jake brake), no more than 6-psi brake applications should be needed to prevent the truck from going too fast.

At no more than 6-psi brake applications, not enough heat is created to present any problems.

Ignoring Advice

If Drivers ignore this advice, they may suddenly find themselves with no brakes as there are no real warning signs – if the brakes are overheated, it’s already too late and serious risks are in play.

If a Driver presses as hard as they can on the brakes, and nothing happens – there simply are no brakes, then there is little or nothing a Driver can do at this point to prevent a possibly deadly collision.

In cases of extreme good luck, Drivers may somehow be able to come to a safe stop or use a runaway lane, but then will likely have a tire fire to deal with, which can be next to impossible to extinguish and will likely lead to loss of the trailer and load and possibly even the tractor, unless they are able to safely separate the units.

Brake Checks

Bison Transport policy is that our Drivers must stop and check their brakes at ALL brake check areas, regardless of whether they are mandatory brake check areas.

Brake check areas can serve more than one purpose. Not only must Drivers use the opportunity to ensure their brakes are properly adjusted, the time spent will also help to dissipate any built-up heat in the brakes. Additionally, if Drivers stop for brake checks as they should, braking over the top of the grade before coming down can be avoided, which also reduces risks.

Brake checks give the Driver an additional opportunity (on top of their Air Brake check that must legally be completed as part of every daily Pre-trip Vehicle Inspection) to ensure that the air compressor reservoir is full, governor is functioning correctly, there are no air leaks, gladhands and airlines are secure, pushrod travel is adjusted properly on all brakes, and drums, brake pads and all other components of the brake system are secure and within tolerances. It also gives Drivers a chance to ensure that wheel hubs are not leaking and have correct oil levels, hubs, bearings and tires are not too hot or showing excessive wear, and that the wheel nut indicators are not indicating any loose lug nuts.