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When you’re driving a vehicle that’s several times heavier than your average car, you need to know how to look after your brakes and how to use them properly. This article covers all the knowledge you’ll need for your theory test for heavy vehicles and passenger carrying vehicles.
Jake brakes, exhaust brakes and retarders
While the service brake is the most powerful brake on a bus or lorry, other braking systems are used because service breaks are friction-based and can overheat quickly on long declines. Well-maintained service brakes will provide even, powerful, consistent braking on all wheels. They are the brakes you will use the most in general driving.
The three main braking systems are called service brakes, secondary brakes and parking brakes. The service brake performs the primary function of stopping the vehicle when you depress the footbrake. The secondary brake system is for use in the event of failure of the service brake. The parking brake should normally only be used when the vehicle is stationary, including if you are making a short stop facing uphill.
A Jake brake is an additional method of slowing a vehicle down. It works by altering the valve timing in the engine. It’s a genericised trademark of Jacbos brake which is a compression release engine brake.
Jake brakes are noisy, so avoid using them in urban areas.
A system for controlling the vehicle’s speed without using the footbrake is called an endurance brake or retarder. It replaces some of the functions of friction-based brakes which are susceptible to brake fade on long downhill slopes. The retarder isn’t usually capable of bringing a vehicle to a standstill, so you have the normal friction-based service brakes for that. These systems mean your brake linings last longer.
Electromagnetic retarders work by applying a magnetic resistance to the prop shaft which, in turn, slows down the wheels. This allows the service brake to stay cool for optimum performance when required.
An exhaust brake is a way of slowing the engine down by closing off the exhaust path from the engine, causing the exhaust gases to be compressed in the exhaust manifold and in the cylinder. Effectively, the engine works backwards by creating negative torque. They’re most efficient when the engine is at high speed and in a low gear, such as when descending a long hill. Using the exhaust brakes can relieve the service brakes, preventing them from becoming hot and failing through over-use.
On very slippery roads take care with engine brakes as they will provide additional braking that could cause a skid.
Brake fade and drying your brakes
Your brakes’ effectiveness will be reduced if you have driven through deep water, such as a ford or flood. You must dry your brakes after driving through water by driving in a low gear with the footbrake lightly applied. Check what’s behind you before you do this. When you are doing it you will feel the brakes begin to bite again.
Brake fade happens when your brakes get too hot. The heat can boil the brake fluid meaning that bubbles form and it loses hydraulic pressure. The heat can also liquefy and vaporise the brake pads dramatically reducing their friction on the disks. Long downhill gradients are the main cause of brake fade.
Changing to a lower gear can help avoid brake fade, as can using a retarder or jake brake. Change down early, i.e. before you are on the slope.
Air brakes
Air brake systems usually have two lines. If your system has three lines, the third is an auxiliary (blue) line. Check with the manufacturer’s instructions what this can be used for. The red line is the emergency line. If there are only two connectors but three lines, don’t connect the auxiliary (blue) line.
You should never coast downhill because air brakes rely on an engine-driven compressor to replenish the air in the brake reservoir tanks. Coasting downhill and relying on the brakes to control your speed could result in a loss of sufficient air pressure to operate the brakes effectively, particularly if the compressor is worn.
In frosty weather a driver can drain the brake air storage tanks daily to prevent moisture freezing in them, which would cause a blockage that can prevent air pressure building up. Most modern vehicles have an automatic draining system.
If the brakes’ air pressure warning light comes on you should stop and seek help without delay as your brakes could be about to fail.
This diagram shows a simple air brake system:
If the brake pedal feels hard then the vacuum pump is not working. You should see a warning light or hear a buzzer.
If you are stationary and the air pressure warning light comes on, don’t release the parking brake because the service brakes might not stop you.
Anti-lock brakes
With anti-lock brakes a driver can push the footbrake firmly and continuously until the lorry or bus comes to a complete stop without risk of locking the wheels. Anti-lock brakes, or ABS, also allow the driver to maintain steering control while braking.
On a bus, the anti-lock braking system warning light should go out once speed increases above 6mph.
Jack-knifing
An articulated lorry is more likely to jack-knife when unladen, on a bend with the driver braking sharply. When a lorry jack-knifes the trailer tries to push the cab around. Jack-knifing can be caused by changing down to too low a gear while braking as the additional engine compression can cause the cab’s drive wheels to lock.
Here’s what it looks like inside the cab when a driver saves a lorry from jack-knifing on a snowy road.
Some lorries have jack-knife protection such as the one shown in this video.
Braking techniques
Progressive braking
Progressive braking puts the safety and comfort of the passengers is your first priority, and helps you get the most out of your vehicle as it reduces tyre wear and fuel consumption. Good forward planning and anticipation will enable you to avoid harsh braking and late, sharp steering. Badly driven vehicles cost more to run and maintain.
Cadence braking
Cadence braking will help you control a vehicle without anti-lock brakes. It’s a way of braking in slippery conditions and needs practice to perfect. It simulates ABS. The driver pumps the brakes to give some steering and braking on a slippery surface. First start by applying the brakes to the point where they lock up, then bring the brake pedal up until the wheels grip, then down again until the wheels lock again. Repeat the process.
On some surfaces, such as loose gravel, locking the wheels will stop you quicker than cadence braking. Cadence braking is less effective than threshold braking.
Threshold braking
Threshold braking requires practice and also for you to know very well how your vehicle performs under brakes. Threshold braking aims to keep tyre slip at an optimal amount by controlling brake pedal pressure. There will be a small amount of wheel lockup, and the driver modulates the brake pedal to maintain a balance between rotating wheels and locked wheels.
Braking emergencies
On a steep hill you will come across escape lanes which can be used if you experience brake failure. They will be indicated with a sign like this. They are a slip road with soft material at the end to stop runaway trucks.
If your brake pedal feels soft or goes to the floor either you are experiencing brake fade, or you have a serious loss of fluid from the hydraulic system. This must be checked and fixed by a qualified person. Do not drive it until this has been done.
Diff lock
When driving on muddy, slippery and loose surfaces you can switch on your diff (differential) lock to give you more grip. Engaging the diff-lock means that power is shared between the driven wheels. This reduces the chances of wheelspin. Remember to switch off the diff-lock as soon as you are on firm ground again, otherwise you could damage the transmission.
Seat belts
Seat belts hold you in place in a crash and under braking. If your lorry or bus is fitted with seat belts, you must wear them unless you have a valid medical exemption or the vehicle is being reversed.
If you use the proper search patterns and see things well in advance, you should avoid most emergencies. However, as part of your IPDE method of driving, expect that other drivers may sometimes proceed when they shouldn’t. This means that you will have to execute your decision in a hurry if you are to avoid a collision. In this section, you'll deal with the techniques you need to control your vehicle during the execution part of an emergency situation. To become skilled in emergency techniques, you need to practise, if possible, with a trained instructor. The rule is simple! Look where you want to go and steer there. Don't look at the tree you want to avoid, look at the gap you want to get through. Always try to brake in a straight line. Get your wheels straight and line up your vehicle so that it can go straight ahead while you're braking. Don't try to brake when your vehicle is turned - you could spin out. (See Braking.) The difference between steering in an emergency situation and steering in a normal driving situation is the speed and amount that you need to turn the wheel. If you do skid and need to recover, turn the wheel to correct your direction of travel. This method just takes practise. The difficult part is knowing when your wheels are straight. At higher speeds, use the "9 and 3" steering method. (See Hand positions.) Twist the wheel without moving your hands on the wheel. When your hands return to "9" and "3," you know your front wheels are straight. Steering around an object involves three movements: Steer Counter-steer Straighten out Timing is crucial, so it's advisable to practise this manoeuvre with an experienced instructor. It's important, after turning around an obstacle, to get the vehicle going straight before you begin a second steering movement. If your choice is between braking or steering, choose to steer. You can steer around an obstacle in a shorter distance than it takes to stop in front of it. Where you have a choice, the best method of dealing with an emergency is to combine braking and steering. Brake first, while you slow down and regain control and finish deciding where you want to go. If you have time and you are feeling calm, threshold brake. If not, lock your four wheels. Regardless of the method of braking you use, take your foot off the brake to steer around the object. Most importantly, do one thing at a time, either brake or steer. If your wheels are locked, the car will go straight ahead regardless of how you turn the steering wheel. If you are driving a vehicle equipped with ABS, the best way to deal with an emergency is to brake hard and steer where you want to go. Provided it's recommended for your vehicle type, it's best to shift to neutral, or declutch, in all emergencies, except when you plan to use the accelerator to get out of trouble. Please refer to your vehicle owner's manual for manufacturer's recommendations in this regard. A skid usually occurs on a slippery surface when there is not enough traction to keep the tires rolling. You will go into a skid when it is wet or slippery if you brake or accelerate too hard or turn too sharply. Regardless of the kind of skid, always shift to neutral (declutch). Turning the wheel in the direction of the skid is correct, but complicated. A much simpler way to decide what way to steer is to look where you want to go and steer there. Never use cruise control when roads are wet or slippery or on gravel. The remedy is the same in any skid resulting from braking, regardless of how many wheels lock. Shift to neutral (declutch) and remove your foot from the brake. Look where you want to go and steer there. By shifting to neutral, you will ensure that the skid does not get worse and you will get the wheels rolling again so that you can steer. You will probably have to correct the steering. Look where you want to go and steer there. This will usually mean steering, counter-steering and straightening out. Sometimes too much acceleration or using cruise control on a slippery surface will cause the vehicle to skid. To correct this situation, shift to neutral (declutch), take your foot off the accelerator, look where you want to go and steer there. Do not touch the brake. Some corrective steering may be necessary. If you turn the wheel too far to the left or right on a slippery surface, the front wheels will skid straight ahead. To correct this, you must shift to neutral (declutch) and turn the wheel back towards the centre. As the wheels move to a position where they are turned less sharply, they will begin to grip again and you will be able to steer. You actually turn the wheel in the opposite direction from which you wish to go until the wheels begin to roll. Only at this point do you look where you want to go and steer there. Sometimes, when a skid has gone too far, the vehicle will start to spin. You may not be able to stop the spinning, but you do have a choice of where it spins. Shift to neutral, if you have time, and lock all four wheels. The vehicle will spin in a straight line, continuing in the direction in which it was last going. Usually, if you do this you can stay on the road. To avoid getting into a skid, first adjust your speed to the conditions, then look well ahead so that you have plenty of time to react slowly and smoothly. If you must make any movements on a slippery surface, make them smoothly and gently and avoid sudden movements of the steering wheel.
Twist the wheel in the direction you wish to go.
Turn the wheel back the other way beyond the centrepoint.
Twist the wheel back to the point where your wheels are straight.
When in a skid, look where you want to go and steer there.
Many collisions are caused by the driver's over-reaction to a possible emergency situation. If you find yourself in an emergency situation, try to remain calm and take the time to think before you act. As a skid develops, the earlier you take action, the smaller the corrective movement required and the greater are your chances of controlling it.
If you drift onto a soft shoulder, it's not what you do that is important, it is what you do not do that counts.
If your right wheels drop onto a soft shoulder, don't jerk the wheel to get back on the road in a hurry and don't brake hard.
Do not take any corrective action immediately, just steer straight along the shoulder, gradually slowing down. Then, when you have slowed and there are no other vehicles around, turn the wheel left and almost immediately (when you feel your front wheel come onto the road) counter-steer and straighten out.
It's a simple procedure as long as you don't steer very much. You should, however, grip the wheel tightly.
If you come off in a critical location, for example, just before a bridge, then treat your return to the road like an emergency lane change and steer, counter-steer, straighten.
With ditches, as with soft shoulders, it's what you don't do that's important.
Don't brake hard, don't turn the wheel violently and don't try to get back on the road. These actions are very likely to cause your vehicle to roll over.
The important thing is to drive down the ditch. The greater the slope of the ditch, the more you will have to steer down the ditch to keep from rolling.
To drive down the ditch, hold the wheel firmly. Look and steer gently down the slope to where you want to go. Stay off the brake. Gradually release the accelerator. If you need to steer to avoid an obstacle, do it slowly and gradually and, if you have a choice, choose the direction that will send you down the slope.
If you suddenly find yourself going into a ditch, do not over-react. Try to resist doing anything until you think about what you must do. You're better off to do nothing than to try the wrong thing.
It's perfectly all right to drive in a ditch to avoid a rollover, provided you don't hit an approach road or something hard. The main cause of rollovers is attempting to return to the road too early. You may have to be towed out, but that is a small price to pay compared to rolling the car.
Gentle ditch
Steep ditch
With a front or rear tire blow-out, do not over-react. Look where you want to go and steer there, holding the steering wheel firmly. Gradually ease off the accelerator and gently brake. Once you have slowed down, steer the vehicle off to the side of the road.
Blow-outs can cause tremendous steering and wheel vibration. Do not be alarmed. Remember, gentle braking will improve stability and reduce steering and wheel vibration.
Rear wheel blow-outs can cause the back of the car to fishtail. Do not over-correct your steering. Just brake gently and steer where you want to go. Remember to shift to neutral (declutch).
Vehicles are manufactured with a two-circuit hydraulic brake system, and total brake failure is very rare. If one half of the system fails, the brake warning light will usually come on when you apply the brakes and you'll have to push much harder to slow or stop the vehicle. Even if the brake pedal goes right to the floor, do not give up. It'll still have stopping power.
You can help slow the vehicle by using the parking brake. Try to avoid having the rear wheels lock as this will cause the vehicle to spin around. By adjusting the parking brake release, you will make it easier to vary the pressure and avoid locking.
Don't pump your brakes. It's the wrong thing to do with a modern brake system. If the vehicle pulls to one side, grasp the wheel firmly, counter-steer and shift to a lower gear. After the car has stopped, do not drive any further. Call for help.
Most vehicles have some form of power assistance for braking and steering to reduce the force necessary to operate the controls.
If the engine stalls, you'll lose your power assistance and will have to apply a great deal more force to the brake or steering wheel to maintain control. Try shifting to neutral and re-starting the engine, then return the shift lever to drive.
If your accelerator sticks, don't panic. Shift to neutral (or declutch), slow down, pull over and stop. Then, turn the key off and try unsticking the pedal with your feet.
If your headlights suddenly go out, immediately slow down to keep your original course, pull over and stop. Check the headlight switch and the dimmer switch. If these don't work, put on the parking lights or hazard lights.
Wild animals are unpredictable but there are times when the risk of a collision is particularly high. Be alert during the months of May and June when animals are drawn to ditches for road salt and to escape biting insects. Animals are also especially active in the late fall and early winter during mating season and migration. The peak times for collisions are dawn and dusk.
Watch your speed
Yellow wildlife warning signs indicate areas of high risk. No matter the season or time of day, it's important to watch for signs of wildlife and reduce your speed accordingly. Slowing down reduces the distance required to stop and decreases the force of impact in the event of a collision.
Be alert
It's important to constantly scan the road from shoulder to shoulder. Being alert is still your best defence to prevent a collision. When you see an animal at the side of the road, slow down and pass by slowly. For night driving, look for the glowing eyes of animals and use your high beams whenever possible.
When encountering an animal, try to do the following:
- Remain calm if an animal appears on the road in front of you. If you have time to stop, do so at a safe distance and stay alert. When one animal crosses the road, others often follow. You can also sound your horn to scare wildlife away from the road.
- If an animal appears suddenly and surprises you, remember to brake firmly and stay in control of your vehicle. Avoid swerving because you may turn into oncoming traffic or roll into the ditch.
When a collision is unavoidable
Sometimes collisions with wildlife are unavoidable even if you take every precaution and remain alert at the wheel. In these circumstances, try to remain calm.
- Aim your vehicle at the spot where the animal came from, not where it's going.
- Try for a glancing blow rather than a head-on encounter and let up on your brake just before you collide. This causes the front of your vehicle to rise slightly and reduces the chances of the animal going through your windshield.
- Hitting an animal can be a traumatic experience. If possible, move to the shoulder and turn on your hazard lights. Take a moment to regain your composure and then assess the damage to your vehicle.
- Don't approach the animal, especially if it appears to be wounded. Injured animals can be dangerous.
- Call the police or your local RCMP detachment if there are human injuries or significant damage to your vehicle. If the damage is less severe, you may continue driving and follow regular SGI claims reporting procedures.
- Call the Conservation Officer Service if there is a dead or injured animal to report.
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