MOUNTAIN DRIVING

The force of gravity plays a major role in mountain driving. If you have a heavy load or a fully loaded bus, you must select lower gears to climb the hills. When going down steep hills, the pull of gravity speeds you up. You must go slow so your brakes can hold you back without overheating. If the brakes become too hot, they may start to "fade." This means that you have to apply them harder and harder to get the same stopping power. When the brakes continue to be used hard, they continue to fade until you cannot slow down or stop at all.

Use of Gears

No matter what size of vehicle you are descending long, steep grades in, going too fast can cause your brakes to fail. Lower gears allow engine compression and friction to help slow the vehicle. This is true whether you have an automatic or a manual transmission.

When you are operating a large vehicle with a manual transmission or a fully loaded bus, do not wait until you have started down a hill to shift down. You could get hung up in neutral and find yourself coasting, which is not only illegal but is also dangerous. Remember: Choose the right gear before starting down a hill.

For older trucks, the rule of thumb for choosing gears is to use the same gear going down a hill that you would use to climb the hill. New trucks have low friction parts and streamlined shapes for fuel economy and often have more powerful engines. This allows them to go up hills in higher gears. They also have less friction and air drag to hold them back when going down a hill. For this reason, operators of newer trucks often have to use lower gears going down a hill than needed to go up the hill.

Proper Braking

When going downhill, brakes tend to heat up. When engaged, the brake pads and shoes rub against the brake disc and drums, creating heat. Brakes are designed to withstand intense heat; however, brakes can fail from excessive heat if you try to slow down from a high speed too many times too quickly. Brakes fade (have less stopping power) when they get hot and may not slow the vehicle.

The correct way to use your brakes for long downhill grades is to go slow enough that fairly light use of the brakes prevents your speed from increasing. When you go slow, the brakes can cool down.

Some operators think that backing off on the brakes from time to time (fanning) allows them to cool enough to prevent overheating. Tests have proven this is not true. Brake drums cool slowly, so the amount of cooling between applications is not enough to prevent overheating. This type of braking requires heavier brake pressure than steady application does. The heavier pressure used on the brakes builds up more heat than the light continuous pressure does; therefore, select the right gear, go slow, and maintain a lighter, steadier use of the brakes.

Escape Ramps

Escape ramps are constructed on most steep mountain grades. They are used to stop runaway vehicles safely without injury to drivers or passengers. Escape ramps use along bed of loose soft material, such as pea gravel or sand, to slow a runaway vehicle. Sometimes, they are used in combination with an upgrade.

VEHICLE RECOVERY

Recovery is a major operation. During any recovery operation, always use a proven procedure. A haphazard approach to a recovery problem or the use of a trial-and-error method can be a costly mistake. Such a mistake can "deadline" the disabled vehicle longer than necessary, cost valuable time, damage equipment, and injure personnel. Self-recovery of vehicles, recovery with wreckers, and recovery with like-vehicles are discussed in this section.

WRECKERS

Recovery, using wrecker trucks, should be performed by trained recovery personnel of Alfa company or the transportation division. An understanding of the ability of the vehicle to winch, lift, and tow is very important. For in-depth information, refer to the operator's manual that relates to the operation of specific equipment and their specific abilities.

Mired Truck

The recovery of a mired truck using a wrecker truck is not always an easy task because it involves the resistance of the load, the approach to the load, and the distance between the wrecker and the mired vehicle. Use a direct pull if the resistance created by the mired vehicle is less than the winch capacity of the wrecker.

CAUTION

Do not hook the winch cable around the bumper on a vehicle. Wrapping the tow cable around the bumper of a mired vehicle will result in a bent bumper.

An example of a simple winching operation is shown in figure 5-6. Some winching operations are more difficult. The mired truck may have a resistance greater than the winch capacity of the wrecker. Also, the wrecker may not be able to align itself with the truck due to terrain. If so, use a 2:1 mechanical advantage and a change of direction pull, as shown in figure 5-7.