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2.15 Emergencies (continued)

Brake Failure

Brakes kept in good condition rarely fail. Most hydraulic brake failures occur for one of two reasons: loss of hydraulic pressure or brake fade on long hills (air brakes are discussed in Section 5).

Loss of Hydraulic Pressure:

When the system will not build up pressure, the brake pedal will feel spongy or go to the floor. Following are things you can do:

  • Downshift - Putting the vehicle into a lower gear will help to slow the vehicle.
  • Pump the brakes - Sometimes pumping the brake pedal will generate enough hydraulic pressure to stop the vehicle.
  • Use the parking brake - The parking or emergency brake is separate from the hydraulic brake system. Therefore, it can be used to slow the vehicle. However, be sure to press the release button or pull the release lever at the same time you use the emergency brake so you can adjust the brake pressure and keep the wheels from locking up.
Find an Escape Route:

While slowing the vehicle, look for an escape route - an open field, side street or escape ramp. Turning uphill is a good way to slow and stop the vehicle. Make sure the vehicle does not start rolling backward after you stop. Put it in low gear, apply the parking brake and, if necessary, roll back into some obstacle that will stop the vehicle.

Brake Failure on Downgrades:

Going slow enough and braking properly will almost always prevent brake failure on long downgrades. Once the brakes have failed, however, look outside your vehicle for something to stop it.

Your best hope is an escape ramp. If there is one, there will be signs posted. Ramps are usually located a few miles from the top of the downgrade. Every year, hundreds of drivers avoid injury to themselves or damage to their vehicles by using escape ramps. Some escape ramps use soft gravel that resists the motion of the vehicle and brings it to a stop. Others turn uphill, using the hill to stop the vehicle and soft gravel to hold it in place.

Any driver who loses brakes going downhill should use an escape ramp if available. If you do not use it, your chances of having a serious accident may be much greater.

If no escape ramp is available, take the least hazardous escape route you can, such as an open field or a side road that flattens out or turns uphill. Make the move as soon as you know your brakes do not work. The longer you wait, the faster the vehicle will go and the harder it will be to stop.

Tire Failure

Quickly knowing you have a tire failure will let you have more time to react. Having just a few seconds to remember what it is you are supposed to do can help you. The major signs of tire failure are:

  • Sound - The loud “bang” of a blowout is an easily recognized sign. Because it can take a few seconds for your vehicle to react, you might think it was another vehicle. But any time you hear a tire blow, you are safest to assume it is yours.
  • Vibration - If the vehicle thumps or vibrates heavily, it may be a sign that one of the tires has gone flat. With a rear tire, that may be the only sign you get.
  • Feel - If the steering feels “heavy,” it is probably a sign that one of the front tires has failed. Sometimes, failure of a rear tire will cause the vehicle to slide back and forth or “fishtail.” However, dual rear tires usually prevent this.

Any of the above signs is a warning of possible tire failure, and you should do the following:

  • Hold the steering wheel firmly - If a front tire fails, it can twist the steering wheel out of your hand. The only way to prevent this is to keep a firm grip on the steering wheel with both hands at all times.
  • Stay off the brake - It is natural to want to brake in an emergency. However, braking when a tire has failed could cause loss of control. Unless you are about to run into something, stay off the brake until the vehicle has slowed down. Then brake very gently, pull off the road and stop.
  • Check the tires - After you have come to a stop, get out and check all the tires. Do this even if the vehicle seems to be handling all right. If one of your dual tires goes, the only way you may know it is by getting out and looking at the tires.
You need to be familiar with what causes hydraulic brake failure and how to handle a failure. Remember that the top 2 causes of brake failure for hydraulic brakes is loss of pressure and brake fade. You must know this for the written exam, even if you plan on driving a commercial vehicle equipped with air brakes.
Pay special attention to the below list. It is important that you know how to recognize a tire blowout and there are questions that may be asked about this on your written exam.

OWI:

Operating While Intoxicated

Review Questions - Click On The Picture To Begin...

If you're driving a vehicle with hydraulic brakes and lose brake pressure, you should do all of the following except:
  • Use the parking brake to slow the vehicle down
  • All of these are steps you should take if you lose brake pressure
  • Downshift to a lower gear to help slow the vehicle
  • Pump the brakes to try and regenerate hydraulic pressure

Quote From The CDL Manual:

Loss of hydraulic pressure: When the system will not build up pressure, the brake pedal will feel spongy or go to the floor. Following are things you can do:

  • Downshift - Putting the vehicle into a lower gear will help to slow the vehicle.
  • Pump the brakes - Sometimes pumping the brake pedal will generate enough hydraulic pressure to stop the vehicle.
  • Use the parking brake - The parking or emergency brake is separate from the hydraulic brake system. Therefore, it can be used to slow the vehicle. However, be sure to press the release button or pull the release lever at the same time you use the emergency brake so you can adjust the brake pressure and keep the wheels from locking up.

TruckingTruth's Advice:

If you are becoming a Class-A licensed truck or bus driver, there is a very low chance you'll drive a commercial vehicle with hydraulic brakes, but you may still be asked a question about hydraulic brakes on the written exam.

Next
All of the following are signs of tire failure except:
  • These area all indications of tire failure
  • A steering wheel feeling "heavy" indicates a possible tire problem
  • Heavy vibration or thumping indicates a tire may have gone flat
  • A loud "bang" can indicate a tire blowout

Quote From The CDL Manual:

Quickly knowing you have a tire failure will let you have more time to react. Having just a few seconds to remember what it is you are supposed to do can help you. The major signs of tire failure are:

  • Sound - The loud "bang" of a blowout is an easily recognized sign. Because it can take a few seconds for your vehicle to react, you might think it was another vehicle. But any time you hear a tire blow, you are safest to assume it is yours.
  • Vibration - If the vehicle thumps or vibrates heavily, it may be a sign that one of the tires has gone flat. With a rear tire, that may be the only sign you get.
  • Feel - If the steering feels "heavy," it is probably a sign that one of the front tires has failed. Sometimes, failure of a rear tire will cause the vehicle to slide back and forth or "fishtail." However, dual rear tires usually prevent this.

TruckingTruth's Advice:

As a professional driver, it is almost guaranteed that you will experience a tire issue during your career. Be sure to recognize the signs of tire blowouts and what it feels like when a tire goes flat. This can be challenging when driving a large vehicle, but driving on a flat tire can cause rim damage and create roadway damage and debris. Check your tires every time you stop.

Prev
Next
Which statement about brake failure is false:
  • Brakes kept in good condition rarely fail
  • Brake fade is usually the cause of brake failure on long hills
  • If sudden and rapid air loss occurs in an air brake system, no brakes can be applied
  • Loss of hydraulic pressure is a common cause of brake failure on non-air brake systems.

Quote From The CDL Manual:

Brake Failure:

Brakes kept in good condition rarely fail. Most hydraulic brake failures occur for one of two reasons:

  • Loss of hydraulic pressure
  • Brake fade on long hills.

TruckingTruth's Advice:

As long as brakes are kept in good condition and pre-trip inspections are regularly performed, the chance of a brake failure is very slim. Most brake failures occur due to operator error on long and steep downgrades. Mechanical failures in air brake systems are normally very easy to spot during pre-trip inspections with various tests on the air system.

Prev
Next
When experiencing rapid tire failure, such as a blowout, you should do all of the following except:
  • Hold the steering wheel very firmly until you come to a complete stop
  • Use the "stab braking" method
  • Stay off the brake and slow down very gradually
  • Once stopped, visually check all tires as well as any damage flying tire debris may have cause to your vehicle

Quote From The CDL Manual:

Hold the steering wheel firmly - If a front tire fails, it can twist the steering wheel out of your hand. The only way to prevent this is to keep a firm grip on the steering wheel with both hands at all times.

  • Stay off the brake - It is natural to want to brake in an emergency. However, braking when a tire has failed could cause loss of control. Unless you are about to run into something, stay off the brake until the vehicle has slowed down. Then brake very gently, pull off the road and stop.
  • Check the tires - After you have come to a stop, get out and check all the tires. Do this even if the vehicle seems to be handling all right. If one of your dual tires goes, the only way you may know it is by getting out and looking at the tires.

TruckingTruth's Advice:

Having a tire blowout is very likely to occur during your driving career. When a blowout occurs, it's important to stay calm. Most accidents from tire blowouts occur due to drivers becoming spooked and overreacting. Stay calm and don't make any sudden or erratic movements. After the initial blowout, do not use your brakes. Allow the vehicle to slow down very gradually and once you're sure you have full control of the vehicle, start using gentle brake pressure and find a safe location to pull over.

Never go into the roadway to remove tire debris. If the debris is causing a traffic hazard, notify authorities about the situation and warn other truckers by using a CB Radio, if equipped..

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Next
What is an escape ramp?
  • A traffic device that enables vehicles that are having braking problems to safely stop
  • A device used to help climb into or out of a truck trailer
  • A ramp to connect an expressway to a side street
  • Another term for an on-ramp, connecting a side street to a major expressway

Quote From The CDL Manual:

Brake failure on downgrades: Going slow enough and braking properly will almost always prevent brake failure on long downgrades. Once the brakes have failed, however, look outside your vehicle for something to stop it.

Your best hope is an escape ramp. If there is one, there will be signs posted. Ramps are usually located a few miles from the top of the downgrade. Every year, hundreds of drivers avoid injury to themselves or damage to their vehicles by using escape ramps. Some escape ramps use soft gravel that resists the motion of the vehicle and brings it to a stop. Others turn uphill, using the hill to stop the vehicle and soft gravel to hold it in place.

Any driver who loses brakes going downhill should use an escape ramp if available. If you do not use it, your chances of having a serious accident may be much greater. If no escape ramp is available, take the least hazardous escape route you can, such as an open field or a side road that flattens out or turns uphill. Make the move as soon as you know your brakes do not work. The longer you wait, the faster the vehicle will go and the harder it will be to stop.

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