Braking Heavy Vehicles

Question 1

How long is the average driver’s reaction time?

Answer 1

3/4 of a second

Question 2

What factors make up total stopping time?

Answer 2

• driver’s perception
• driver reaction
• brake lag
• brake time

Question 3

How many seconds behind should larger trucks and buses be behind the car in front of them?

Answer 3

5

Question 4

How much more stopping power is required if the speed is doubled?

Answer 4

4 times the power

Question 5

How much more stopping power is needed if the weight is doubled?

Answer 5

2 times the power

Question 6

How much more stopping power is required if both the speed and weight are doubled?

Answer 6

8 times the power

Question 7

What is brake fade and how can it affect a vehicle?

Answer 7

Brake fade occurs when the brakes overheat from overuse. It can take longer to stop, especially if speed is not already controlled.

Question 8

What are the main types of retarders?

Answer 8

-engine, exhaust, electric driveline, hydraulic driveline

Question 9

When is an engine retarder more efficient?

Answer 9

At a higher RPM and lower speed.

Question 10

How do you ensure a smooth controlled stop every time?

Answer 10

• ensure an adequate following distance
• travel at a speed that allows you to see a safe distance ahead
• use good braking skills

Question 11

What factors, other than driver actions, will affect safe vehicle braking?

Answer 11

To stop safely, ensure that your brakes are correctly adjusted, your load is balanced and your tires are in good condition. Also, be certain that your tires
are properly inflated

Question 12

What braking technique should be used on icy roads? And why?

Answer 12

You should use extremely light pressure on the brakes. This will stop the wheels locking up. It is better to have a spinning wheel than a locked wheel.

Question 13

When should you put on tire chains?

After you install them, and begin driving, what should you do?

Answer 13

Before a snowy or icy slope.

Check them at the first safe opportunity, for tightness.

Question 14

On a hill, what are some notes to remember regarding gears? (2)

Answer 14

You should use a lower gear when descending, than you would for ascending.
Never change DOWN gears on a downslope; UNLESS you can control the speed with retarder or engine compression.

Question 15

How can you ensure that you won’t need to use the service brakes when descending a hill?

Answer 15

Ensure that you keep an appropriate, safe speed and low gear and use the retarding device.

Question 16

If you haven’t been able to control the speed down a hill, what should you do?

Answer 16

Brake gently to reduce the speed by 10-15km/hr
Downshift to a lower main gear.
(Be careful using this procedure on icy roads)

Question 17

Explain what to do if you need to drive through a pool of water on the road.

Answer 17

Slow down. Put foot over the brake. When driving through the water put a slight but constant drag on the brakes. After the pool, apply a gentle constant pressure again, for a short distance, to dry out the brakes.

Question 18

Wha can cause jack-knifing?

Answer 18

Improper braking technique, and improper use of retarders.

Question 19

What are some things to remember with EMERGENCY Braking?

Answer 19

-Apply firm, hard continuous pressure to the brake pedal until the vehicle stops.
• Don’t pump the brakes — this turns the system on and off.
• Don’t be alarmed by brake noise, pedal movement or shudder. This is normal. Keep applying firm pressure.
• Be extremely cautious when steering around obstacles. Remember that steering and handling characteristics will be affected by the size and load of
the vehicle you’re driving, and by the trailer you may be towing.
• When you operate combination vehicles, make sure you know which of the units have ABS. If the tractor and trailers do not all have ABS, apply the
brakes as if you were operating a combination without ABS.

Question 20

Explain ATC and how it works.

Answer 20

Automatic Traction Control - works by sensing if one wheel is spinning and braking that wheel, transferring power to the other side.