ORIENTACIONES METODOLÓGICAS

» Skids

» Emergency steering techniques

» Leaving the road

» Using the horn

» Dangerous vehicle emergencies

» Brake failure

» Tyre failure

» Fires

» Test yourself questions

Emergencies

Emergencies are those situations in which only your quick response can prevent a crash.

Emergency braking

If someone pulls out in front of you, it is a natural response to brake. This is a good response if there is enough distance to stop and you use your brakes the right way.

Braking the proper way

You need to brake in a way that will keep your vehicle in a straight line and allow you to turn if you have to.

The best way of doing this is:

» apply your brakes just hard enough to almost lock the wheels

» if the vehicle starts to skid, release the brake so the vehicle straightens out

» as soon as the wheels start rolling, apply the brakes again a bit more gently.

It takes time for the wheels to start rolling again after you release the brakes. If you use the brakes again before the wheels are rolling, the vehicle will not straighten out.

Emergency braking does not mean stepping on the brake pedal as hard as you can. This will only lock the wheels causing a skid and possibly causing your load to shift. Proper braking will prevent this and allow you to stop in the shortest possible distance.

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Skids

Skids occur when tyres lose their grip on the road. Skids are caused by:

» over-braking – when you apply the brakes too hard and lock the wheels

» over-steering – when you turn the wheels more sharply than the vehicle can turn

» giving too much power to the drive wheels, causing them to lose grip and spin.

Most skids result from driving too fast for road conditions. If you adjust your speed to suit the road conditions you will not get into a skid.

ehicle emergencies

Drive-wheel skids

The most common sort of skid is where the drive wheels lose traction because of applying the brakes too hard or giving too much power to the drive wheels, causing them to spin and lose grip. These usually happen on slippery surfaces. They are stopped by easing off the accelerator.

Drive-wheel braking skids

These happen when you put too much pressure on the brake pedal for the road conditions. The drive wheels lock and the vehicle skids.

In a rigid vehicle, the whole vehicle will slide sideways. A rigid vehicle with trailer attached will be even more difficult to control and correct.

In an articulated vehicle, or when towing a trailer, a rear wheel skid is worse because:

» the trailer pushes the back of the prime mover or rigid vehicle sideways

» the trailer can jack-knife – skidding around until it hits the cab of the prime mover.

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Correcting a drive-wheel braking skid

Stop braking. This lets the drive wheels start rolling again, restores traction and the wheels stop sliding sideways.

Steer in the direction you want to go.

Counter-steer. As the vehicle comes back on course, it has a tendency to keep on turning. Correct this by briefly steering in the opposite direction, to counter the skid.

Trailer skids

You have probably seen skid marks on the highways caused by trucks. Imagine what could happen if a car was behind the truck when this happened.

These skids are often caused when heavy vehicles are travelling empty and drivers have forgotten to adjust their trailer brake proportioning valve after unloading their cargo and travelling lightweight.

Some modern vehicles do not have trailer brake proportioning valves, but if yours does, you must know how to use it properly.

Remember to adjust your trailer brake proportioning valve when you unload part of a load, change loads, or when you are running empty.

Check the vehicle manufacturer’s handbook for details on adjusting the proportioning valve.

Front wheel skids

In a front wheel skid, the front end tends to go straight ahead, no matter how you turn the steering wheel. If the surface is slippery you can fail to make it around a turn or a bend.

When you have a front wheel skid, release the brakes and make sure the wheels are turning before using the brakes again.

Excessive speed is the main cause, but another contributing factor may be poor loading of the vehicle.

Evasive steering

Stopping may be the safest thing to do in an emergency.

When you do not have enough room to stop, or you aren’t sure whether you can stop, you will have to steer and turn away from whatever is in your path.

Remember, you can often turn more quickly than you can stop. But also remember that a heavy vehicle will tend to continue in a straight line, because of its mass and momentum.

A firm grip is essential in an emergency. Keep both hands on the steering wheel whenever possible. See the next section for tips on emergency steering techniques.

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