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2.16 Skid Control and Recovery

A skid happens whenever the tires lose their grip on the road. This is caused by one of four ways:

  • Over-braking - Braking too hard and locking up the wheels. Skids also can occur when using the speed retarder when the road is slippery.
  • Over-steering - Turning the wheels more sharply than the vehicle can turn.
  • Over-acceleration - Supplying too much power to the drive wheels, causing them to spin.
  • Driving too fast - Most serious skids result from driving too fast for road conditions. Drivers who adjust their driving to conditions do not over-accelerate and do not have to over-brake or over-steer from too much speed.
  • By far the most common skid is one in which the rear wheels lose traction through excessive braking or acceleration. Skids caused by acceleration usually happen on ice or snow. They can easily be stopped by taking your foot off the accelerator (if it is very slippery, push the clutch in. Otherwise, the engine can keep the wheels from rolling freely and regaining traction).

    Drive Wheel Skids

    Rear-wheel braking skids occur when the rear-drive wheels lock. Because locked wheels have less traction than rolling wheels, the rear wheels usually slide sideways in an attempt to “catch up” with the front wheels. In a bus or straight truck, the vehicle will slide sideways in a “spin out.” With vehicles towing trailers, a drive-wheel skid can let the trailer push the towing vehicle sideways, causing a sudden jackknife (see Figure 2-15).

    Figure 2-15
    Tractor Jackknife

    Do the following to correct a drive-wheel braking skid:

    • Stop braking - This will let the rear wheels roll again and keep the rear wheels from sliding any further. If on ice, push in the clutch to let the wheels turn freely.
    • Turn quickly - When a vehicle begins to slide sideways, quickly steer in the direction you want the vehicle to go down the road. You must turn the wheel quickly.
    • Counter-steer - As a vehicle turns back on course, it has a tendency to keep right on turning. Unless you turn the steering wheel quickly the other way, you may find yourself skidding in the opposite direction.

    Learning to stay off the brake, turn the steering wheel quickly, push in the clutch and counter-steer in a skid takes a lot of practice. The best place to get this practice is on a large driving range or “skid pad.”

    Front Wheel Skids

    Most front-wheel skids are caused by driving too fast for conditions. Other causes are lack of tread on the front tires, and cargo loaded so not enough weight is on the front axle. In a front-wheel skid, the front end tends to go in a straight line regardless of how much you turn the steering wheel. On a very slippery surface, you may not be able to steer around a curve or turn.

    When a front-wheel skid occurs, the only way to stop the skid is to let the vehicle slow down. Stop turning and/or braking so hard. Slow down as quickly as possible without skidding.

    Test Your Knowledge

    • Stopping is not always the safest thing to do in an emergency. True or False?
    • What are some advantages of going right instead of left around an obstacle
    • What is an escape ramp?
    • If a tire blows out, you should put the brakes on hard to stop quickly. True or False?

    These questions may be on the written exam. If you cannot answer all of them, study Sections 2.15 and 2.16.

    2.17 Accident Procedures

    When you are in an accident and not seriously hurt, you need to act to prevent further damage or injury. The basic steps to be taken at any accident are:

    • Protect the area.
    • Notify authorities.
    • Assist the injured.

    Protect the Area

    The first thing to do at an accident scene is to keep another accident from happening at the same spot.

    • If your vehicle is involved in the accident, try to get it to the side of the road. This will help prevent another accident and allow traffic to move.
    • If you are stopping to help, park away from the accident. The area immediately around the accident will be needed for emergency vehicles.
    • Put on your flashers.
    • Set out reflective triangles to warn other traffic. Make sure they can be seen by other drivers in time for them to avoid the accident.
    • Do not put road flares on the ground near wrecked vehicles. Road flares could ignite any leaking flammable liquids.

    Notify Authorities

    If you have a CB, put out a call over the emergency channel before you get out of your vehicle. If not, wait until after the accident scene has been properly protected, then phone or send someone to phone the police. Try to determine where you are so you can give the exact location.

    Assist the Injured

    If a qualified person is at the accident and helping the injured, stay out of the way unless asked to assist. Otherwise, do the best you can to help any injured parties:

    • Do not move a severely injured person unless the danger of fire or passing traffic makes it necessary.
    • Stop heavy bleeding by applying direct pressure to the wound.
    • Keep the injured person warm.
    While you probably don't need to memorize these definitions, you should be familiar with the meaning of each.
    This is a simple concept, but one which comes up from time to time on the written exam. Just understand that to stop an acceleration skid, you need to take your foot off the accelerator.
    A jackknife occurs because the trailer tires have less traction than the tractor tires (or the tractor tires have less traction than the trailer tires). The only way to correct a truck or trailer jackknife is to somehow regain traction. This usually requires that you release the brakes so the wheels can turn freely.
    While you don't need to memorize the below list, you should familiarize yourself with these concepts and be prepared to answer questions about this on the written exam.
    Some questions may be asked about a front wheel skid and how to correct it.
    This is very important! The below list should not only be memorized, but should be memorized in order. Questions about accident procedures are asked about very frequently on the written exam. You have to know what to do and in what order to do it. Study this until you have the order memorized!
    You should absolutely never move an injured person unless you are qualified to do so or the person's life is in immediate danger due to fire or passing traffic. The best thing you can do is protect and secure the accident scene and wait until professional help arrives.

    CDL:

    Commercial Driver's License (CDL)

    A CDL is required to drive any of the following vehicles:

    • Any combination of vehicles with a gross combined weight rating (GCWR) of 26,001 or more pounds, providing the gross vehicle weight rating (GVWR) of the vehicle being towed is in excess of 10,000 pounds.
    • Any single vehicle with a GVWR of 26,001 or more pounds, or any such vehicle towing another not in excess of 10,000 pounds.
    • Any vehicle, regardless of size, designed to transport 16 or more persons, including the driver.
    • Any vehicle required by federal regulations to be placarded while transporting hazardous materials.

    OWI:

    Operating While Intoxicated

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

    What is a reason Drive-Wheel Skids occur?
    • The front wheels lock and the drive wheels do not
    • The rear tires have more tread than the front tires
    • The rear tires have more friction than the front tires
    • The rear drive wheels lock up

    Quote From The CDL Manual:

    Rear-wheel braking skids occur when the rear-drive wheels lock.

    Next
    What is the best way to recover from a Front-Wheel Skid?
    • Let the vehicle slow down without turning or braking hard
    • Accelerate out of the skid
    • Quickly steer in the opposite direction you want the vehicle to go
    • Engage the parking brake so all wheels have even brake pressure

    Quote From The CDL Manual:

    When a front-wheel skid occurs, the only way to stop the skid is to let the vehicle slow down. Stop turning and/or braking so hard. Slow down as quickly as possible without skidding.

    Prev
    Next
    At an accident scene, you should assist the injured by doing any of the following except:
    • Do not move a severely injured person unless the danger of fire or passing traffic makes it necessary
    • Keep the injured person warm
    • Help the injured out of their damaged vehicle
    • Stop heavy bleeding by applying direct pressure to the wound

    Quote From The CDL Manual:

    If a qualified person is at the accident and helping the injured, stay out of the way unless asked to assist. Otherwise, do the best you can to help any injured parties:

    • Do not move a severely injured person unless the danger of fire or passing traffic makes it necessary.
    • Stop heavy bleeding by applying direct pressure to the wound.
    • Keep the injured person warm.
    Prev
    Next
    When involved in an accident, when should you notify authorities?
    • After the accident scene has been properly protected
    • Notifying authorities should be the first thing you do after an accident
    • If you're involved in an accident, let someone else contact the authorities
    • Assist the injured first, then notify authorities

    Quote From The CDL Manual:

    If you have a CB, put out a call over the emergency channel before you get out of your vehicle. If not, wait until after the accident scene has been properly protected, then phone or send someone to phone the police. Try to determine where you are so you can give the exact location.

    TruckingTruth's Advice:

    If you're in an accident, your initial reaction may be to call the authorities immediately. But many accidents result in a "secondary accident" and often times, those crashes are far more severe than the original accident. Before doing anything, try to secure the scene to avoid any secondary accidents, then contact the authorities. Make sure you memorize the order in which things should be done at an accident scene:

    1. Protect the area
    2. Notify authorities
    3. Assist the injured

    Prev
    Next
    When at the scene of an accident with injuries, when should you assist the injured?
    • Assist the injured after you have protected the area, but before you have notified authorities
    • You should never assist the injured until authorities have arrived
    • Assist the injured only after you have protected the area and notified authorities
    • Assist the injured immediately

    Quote From The CDL Manual:

    If a qualified person is at the accident and helping the injured, stay out of the way unless asked to assist. Otherwise, do the best you can to help any injured parties:

    • Do not move a severely injured person unless the danger of fire or passing traffic makes it necessary.
    • Stop heavy bleeding by applying direct pressure to the wound.
    • Keep the injured person warm.

    TruckingTruth's Advice:

    If you are the first one on the scene of a serious accident, you may want to help the injured right away. But make sure you secure the scene of the accident first to avoid any additional collisions. You should then notify the authorities before attempting to assist an injured person. Make sure you memorize the order of recommended accident procedures:

    1. Protect the area
    2. Notify authorities
    3. Assist the injured

    Prev
    Next
    The following are all causes of Front-Wheel Skids except:
    • Driving too fast for conditions
    • All of these are reasons for front-wheel skids
    • Too much tread on the front tires
    • Cargo loaded so not enough weight is on the front axle

    Quote From The CDL Manual:

    Front-Wheel Skids - Most front-wheel skids are caused by driving too fast for conditions. Other causes are lack of tread on the front tires, and cargo loaded so not enough weight is on the front axle. In a front-wheel skid, the front end tends to go in a straight line regardless of how much you turn the steering wheel. On a very slippery surface, you may not be able to steer around a curve or turn.

    When a front-wheel skid occurs, the only way to stop the skid is to let the vehicle slow down. Stop turning and/or braking so hard. Slow down as quickly as possible without skidding.

    Prev
    Next
    After being involved in an accident, you should protect the area. All of the following are ways to protect the area except:
    • Set out reflective triangles to warn other traffic
    • Activate your emergency flashers
    • If possible, move your vehicle to the side of the road
    • Put road flares on the ground near disabled vehicles

    Quote From The CDL Manual:

    The first thing to do at an accident scene is to keep another accident from happening at the same spot.



    • If your vehicle is involved in the accident, try to get it to the side of the road. This will help prevent another accident and allow traffic to move.

    • If you are stopping to help, park away from the accident. The area immediately around the accident will be needed for emergency vehicles.

    • Put on your flashers.

    • Set out reflective triangles to warn other traffic. Make sure they can be seen by other drivers in time for them to avoid the accident.


    • Do not put road flares on the ground near wrecked vehicles. Road flares could ignite any leaking flammable liquids.

    TruckingTruth's Advice:

    As long as you always practice safe driving techniques, you probably will never be involved in a major accident. However, it is very likely you'll see a major accident occur or be one of the first people on scene. First and foremost, remember to protect yourself. Many good samaritans end up injuring themselves by stepping into a traffic lane, slipping on fluids spilled onto the roadway, or cutting themselves on debris from the accident. Don't become another victim!

    While using road flares may be ok in some situations, remember that after an accident, flammable liquids may leak and spread along the ground, so it's best to use warning devices which don't have an ignition source, such as reflective warning triangles.

    Prev
    Next
    During a drive-wheel braking skid, you should:
    • Apply more brake pressure to slow the vehicle down
    • Keep the steering wheel firm and straight
    • None of these answers are correct
    • Turn the steering wheel in the opposite direction you want the vehicle to go

    Quote From The CDL Manual:

    Rear-wheel braking skids occur when the rear-drive wheels lock. Because locked wheels have less traction than rolling wheels, the rear wheels usually slide sideways in an attempt to "catch up" with the front wheels. In a bus or straight truck, the vehicle will slide sideways in a "spin out." With vehicles towing trailers, a drive wheel skid can let the trailer push the towing vehicle sideways, causing a sudden jackknife.


    Do the following to correct a drive-wheel braking skid:




    • Stop braking This will let the rear wheels roll again and keep the rear wheels from sliding any further. If on ice, push in the clutch to let the wheels turn freely.

    • Turn quickly When a vehicle begins to slide sideways, quickly steer in the direction you want the vehicle to go down the road. You must turn the wheel quickly.

    • Countersteer As a vehicle turns back on course, it has a tendency to keep right on turning. Unless you turn the steering wheel quickly the other way, you may find yourself skidding in the opposite direction.



    Learning to stay off the brake, turn the steering wheel quickly, push in the clutch and countersteer in a skid takes a lot of practice. The best place to get this practice is on a large driving range or "skid pad."

    Prev
    Next
    If you're involved in an accident and not seriously hurt, you should do the following in which order?
    • Protect the area, assist the injured, notify authorities
    • Protect the area, notify authorities, assist the injured
    • Assist the injured, protect the area, notify authorities
    • Notify authorities, protect the area, assist the injured

    Quote From The CDL Manual:

    When you are in an accident and not seriously hurt, you need to act to prevent further damage or injury. The basic steps to be taken at any accident are:

    1. Protect the area.
    2. Notify authorities.
    3. Assist the injured.

    TruckingTruth's Advice:

    It's important to memorize this list in order as it is a frequently asked question on the DOT written exam. Also understand the meaning of each:

    • Protect the area - The first thing to do at an accident scene is to keep another accident from happening at the same spot.
    • Notify Authorities - If you have a CB, put out a call over the emergency channel before you get out of your vehicle. If not, wait until after the accident scene has been properly protected, then phone or send someone to phone the police. Try to determine where you are so you can give the exact location.
    • Assist the injured - If a qualified person is at the accident and helping the injured, stay out of the way unless asked to assist. Otherwise, do the best you can to help any injured parties:
      • Do not move a severely injured person unless the danger of fire or passing traffic makes it necessary.
      • Stop heavy bleeding by applying direct pressure to the wound.
      • Keep the injured person warm.
    Prev
    Finish
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