Jack-knifing occurs when the tractor unit is pushed by the semi-trailer pivoting around the coupling (fifth wheel). This is more likely to occur with an unladen vehicle.

If you overfill the engine with oil, you could cause the engine to build up too much pressure when it's running. This could cause damage to oil seals and gaskets.

A flashing amber light is shown at pelican crossings, but not at puffin crossings. Puffin crossings have sensors that detect when pedestrians are using the crossing.

The blue (auxiliary) line isn't used when connecting to a two-line system. Follow the manufacturer's instructions about what to do with this third line.

You're responsible for the safety of the load you're carrying. At no time should the load endanger other road users. It's vital that you make sure your load is secure and safely distributed on your vehicle. How you do this will depend on the

• bulk
• weight
• type of vehicle you're driving (flat bed, curtain side, etc)
• nature of the load.

You'll need to identify the sign in time, so that you can select an appropriate gear.

The differential allows the drive wheels to rotate at different speeds; this is necessary for the vehicle to negotiate corners and bends. On a slippery surface, however, it can cause problems: if one wheel has less traction, it can spin, resulting in a complete loss of drive. The 'diff-lock' prevents the wheels from turning independently and so helps to stop this happening.

You should always allow engines fitted with turbochargers to idle for about a minute before stopping the engine. This prevents the turbine bearings from being starved of oil.

Modern large vehicles are fitted with power-assisted steering. If the steering feels heavy, then there's likely to be a fault, which should be investigated and repaired as soon as possible.

When following cyclists onto a roundabout, be aware that they might not take the exit you expect them to. Cyclists approaching in the left-hand lane may be turning right. They may not have been able to get into the correct lane due to heavy traffic, so give them room.

Use your air conditioning only when it's absolutely necessary. Running it continuously increases overall fuel consumption by up to 15%.

Many vehicles are very powerful and can maintain speed even when climbing a gradient. Even if your vehicle is capable of maintaining speed, you can still use the crawler lane to make it easier for other road users to overtake safely.

Before driving into a tunnel, you should take off your sunglasses. If you don't, you'll find that your vision is restricted - even in a tunnel that appears to be well lit.

Take your time when you're using walkways at high levels. Spilt fuel can make the surface slippery and increase the risk of falling.

If a police officer signals for you to stop, stop as soon as possible in a safe place on the left.

Power-assisted steering operates when the engine is running. If a fault develops, much greater effort is required to turn the steering wheel. Don't attempt to drive a vehicle if you're aware of a fault in the power-steering system.

Indicate your intentions in good time, so that both the motorcyclist and pedestrians know you plan to turn right. You should note all potential hazards and keep checking as you turn.

Although they're advised to wear clothing that's bright or reflective, motorcyclists often wear clothing that's mainly black. This can make them difficult to see, so you must look carefully for them.

You mustn't park or stop on a road marked with double white lines (even where one of the lines is broken) except to pick up or set down passengers.

If you demount the body on a poor or soft surface, there's a danger of it sinking and becoming difficult to handle. Always think carefully before you demount the body and be sure that the site is suitable.

Some weight restrictions apply to heavy goods vehicles only and not to passenger-carrying vehicles. Look for a plate beneath a restriction sign that indicates this. Road signs show weight restrictions in various ways. You should make yourself familiar with all of them, so that you're in no doubt about their meaning and relevance.

To make sure it's safe, you must use the mirrors well before you make any manoeuvre. For example, you need to use them before moving off, turning, overtaking, slowing or stopping, opening a door, or changing direction, lanes or speed.

Expect a motorcyclist who makes a quick glance over their shoulder to be changing direction. They should do this before turning. By observing this, you'll get an early clue of their intention.

Drivers of vehicles carrying dangerous goods are required to hold an ADR driver training certificate. This certificate is valid for five years and is issued by DVLA when you've attended an approved course and successfully completed the examination.

When air is compressed, moisture condenses and collects in the air tanks. This can find its way along the network of pipes connected to the brakes. In frosty weather, the moisture can freeze in the pipes, blocking them completely. On modern vehicles, the air is dried before it's compressed and the air tanks drain automatically to shed any moisture. On older vehicles, the air tanks need draining manually.

Pedestrians use push-button controls to activate the signals. Pelican crossings have no red-and-amber stage before green. Instead, they have a flashing amber light. This means you must give way to pedestrians on the crossing, but you may proceed if the crossing is clear.

A driver's week is defined as a period from 00.00 hours on Monday to 24.00 hours the following Sunday.

Don't move a casualty who's in a safe place, as this could worsen any injury they may have. Only move a casualty if they're in danger - for example, from passing traffic. You may also need to move them if you need to give lifesaving first aid, such as clearing their airway.

A sleeper cab can create extra blind spots. Look out for vehicles just to the rear offside and nearside of your cab - they could soon become hidden in your blind spots.

If you're using a vehicle equipped with an analogue tachograph, you'll need at least one chart for every 24 hours. Your employer should supply you with enough tachograph charts for your entire journey.

Many buses and coaches have a large panel of warning lights on the dashboard. A system check built into the ignition system will allow you to check that all the warning-light bulbs are working before you start your journey. If a warning light stays on, there's a fault. Have it checked before continuing. Remember, your passengers' lives are in your hands.

Children getting off the bus will be hidden from your view, and they may not be able to see you. Even if they can see you, they may have poor judgement of danger. You should drive slowly as you pass the bus and be ready to stop.

Gently tilt the unconscious person's head to clear their airway. Check for at least 10 seconds that the casualty is breathing by looking for movement in the chest, listening for sounds and feeling for breath on your cheek. Get someone to call the emergency services.

Vehicles such as motorcycles, bicycles and caravans could be blown off course by strong winds. You should be aware that your vehicle could cause additional buffeting when you overtake, so allow them plenty of room.

The maximum permitted length of vehicle includes any trailer being towed. Make sure you know the total length of your vehicle.

When approaching a tunnel, switch on your dipped headlights. Be aware that your eyes might need to adjust to the sudden darkness. You may need to reduce your speed.

You must take care when approaching any hazard where height is limited. Know the height of your vehicle and what you can drive under safely. If you aren't sure that it's safe, take another route.

Warn other traffic of the incident, without putting yourself or others at risk. Once the danger of further collisions is dealt with, call the emergency services. While you're waiting for them to arrive, keeping casualties or witnesses calm is important, but never offer a cigarette because of the risk of fire.

On a motorway where there's a long uphill gradient, there may be a crawler lane. This helps the traffic to flow by making an extra lane available on the left for slower, heavy vehicles.

When the roads are wet, have consideration for pedestrians walking or standing near the kerb.

You must stop in a safe place as soon as possible. The curtain might be the only support for a slipped load, so don't open it before checking. Check the load by carefully opening the rear door or opposite curtain, if it shows no sign of bulging.

Never attempt to change direction to the right without checking your right-hand mirror. A motorcyclist might not have seen your signal and could have decided to overtake. This action should be a matter of routine.

Motorcyclists can often pass slow or stationary traffic because of the relatively small size of their vehicle. Take a last look in your right-hand mirror to check for motorcyclists and so avoid turning across their path.

During high winds, one of the lanes on a high bridge might be closed to traffic to create a buffer lane. The buffer lane is kept free to prevent vehicles from being blown into the path of other road users in the next lane. The closure of this lane may cause traffic congestion and delay.

It's important to use a low gear and keep the engine speed high to prevent water from entering the engine through the exhaust system. In these circumstances, it may be necessary to slip the clutch to keep the road speed as low as possible.

Some drivers might emerge from a junction when it's not safe to do so. In this situation, understand that other drivers might make mistakes. Don't intimidate them by driving aggressively to teach them a lesson.

The marker boards should be red and white. They must be kept clean and independently lit at night and in poor visibility, so that other road users can see them.

When the lights turn to green, you may drive on, but only if the crossing is clear. You should wait for any pedestrians to finish crossing, regardless of their age. Allow them to cross the road at their own pace; don't try to hurry them in any way.

Some vehicles are fitted with an audible warning that sounds when the vehicle is reversing. This is an effective way to warn pedestrians and other road users of a reversing vehicle, but it doesn't take away the need to use effective observation all around your vehicle before and while you're reversing. Don't use the device in built-up areas between 11.30 pm and 7.00 am. Have consideration for the residents and don't disturb them with excessive noise.

Rain makes the road surface slippery and reduces tyre grip. Doubling your separation distance should allow you the extra time and space you'll need to slow down and stop safely.

The only effective solution to driver sleepiness is to stop in a safe place and take a break.

On multi-axled vehicles, the inside wheels on the rear twin-axle are the most difficult to check for punctures and damage. A deflated tyre will transfer the weight to the second tyre of the twin-axle pair. This will overload it and could cause it to burst.

As well as a height restriction, the tunnel may have a restriction on the available width of headroom for high vehicles. The advance warning gives you the opportunity to find another route if your vehicle is too high or wide to drive through the tunnel.

High-value cargoes are often targeted by thieves. Operators are recommended to seek advice from their local crime-prevention officer to help prevent their vehicles and loads from being stolen.

Some medicines can have side-effects that affect your driving. Ask your doctor whether you'll be safe to drive while taking the medicine that's been prescribed.

Slow down and be ready to stop if you see animals in the road ahead. Animals are easily frightened by noise and by vehicles passing too close to them. Stop if signalled to do so by the person in charge of the animals.

If you're driving an empty curtain-sided vehicle, you can help to lower the resistance to side wind if you tie the curtains open. The air will then be able to flow across the flat bed of the vehicle. This will reduce any loss of control, particularly when crossing exposed viaducts or bridges.

Depending on road speed, pressing the accelerator pedal firmly to the floor will activate a switch that allows the gearbox to select a lower gear for improved acceleration.

Anti-lock braking systems sense when the wheels are about to lock. The sensor control releases the brakes and immediately applies them again. It will do this many times per second. This both prevents skidding and enables the driver to steer - something that's impossible when the steering wheels are skidding.

Always use the MSM routine when you're approaching a hazard. M - Mirrors: check the position of the traffic behind you. S - Signal: signal your intention to slow down or change course in good time. M - Manoeuvre: a manoeuvre is any change in position, from slowing or stopping the vehicle to turning off a busy road.

Drivers are required to take 35 hours of training every five years to maintain their Driver CPC. This can be split into shorter sessions of at least seven hours each. These can be spread over the five years, so effectively one day's training is taken each year. The penalties for non-compliance are the same as those for driving without a licence.

It's compulsory for drivers and passengers to wear seat belts. However, if you're making deliveries that are less than 50 metres apart, you may leave the seat belt undone. It would be impractical to keep fastening and unfastening your seat belt over such short distances.

Some lanes are set aside for certain types of vehicle. Signs and road markings show the authorised vehicles in words or pictures. There's usually also a sign showing the times that the lane is in operation. Some lanes might only be in operation for a short time. Check the sign and only use the lane if you're allowed to do so.

If you're only carrying half a load on a double-deck lorry, this should be carried on the lower deck whenever possible. With only the top deck loaded, your lorry is top-heavy and at risk of overturning as you drive around bends or corners.

Always check carefully for cyclists when emerging from a junction. Bicycles, being much narrower than any other vehicle, can be quite difficult to see.

In extremely cold weather, you'll have to use diesel fuel with anti-waxing additives to stop the fuel lines from freezing up. During the winter months, these additives are usually put in by the fuel companies.

Take care to secure caps and tank hatches. Diesel is very slippery and, if spilled on the road, it's particularly dangerous to motorcyclists.

Hazardous substances in transit are readily identified by a diamond-shaped warning label. This label carries other information to identify the type of hazard more specifically, such as

• flammable gas
• toxic gas
• corrosive agents.

These are just some of the types of hazard encountered. Strict regulations apply to the storage and carriage of these goods. All drivers of this type of load must receive specific certificated training.

The pump creates a vacuum in the servo unit. This reduces the amount of pressure you need to apply to the brake pedal. Without this vacuum, it's extremely difficult to press the brake pedal down.

Always maintain a safe following distance from the vehicle in front. If another vehicle pulls into the gap, slow down to re-establish a safe following distance. Following too close is dangerous and places you and other road users in unnecessary danger; your view of the road ahead will be seriously reduced, and you won't be able to see or plan effectively.

Only change lanes if doing so won't inconvenience another road user. Merging drivers have a responsibility to give way, if necessary, and not force their way onto the main carriageway. Planning ahead will ensure you're prepared to deal with these situations.

You'll generally see this sign at the approach to a pedestrian-only zone.

White boxes allow you to unload at any time, but during the day the length of stay is restricted. You should check nearby signs for the specific times. At other times, when it's not so busy, there may not be any restrictions on parking.

Before leaving your vehicle parked, you must stop the engine. The parking brake must be set and the vehicle should be safe and secure when you leave the cab.

If convicted, the current fine for each illegal immigrant brought into the UK is £2000. This fine can be imposed on each responsible person; this includes the vehicle driver, owner and hirer.

When using a lorry-mounted crane, stabilisers should always be used. All drivers should be fully trained and regularly tested on their competence in using stabilisers.

The view you get in your mirrors may vary, depending on the size of the trailer and the load it carries. Always adjust your mirrors to ensure that you have the best possible view down each side of the trailer before you drive away.

A toucan crossing is signal-controlled, but unlike a pelican crossing it doesn't have a flashing amber light in the sequence. Cyclists and pedestrians cross together, and cyclists are allowed to ride their bicycles over the crossing.

Switch off your fog lights when fog starts to clear and visibility improves to more than 100 metres (328 feet). Don't leave your fog lights on when the fog has cleared, because they can cause unnecessary glare or distraction for other drivers.

Alcohol can increase confidence to a point where a driver's behaviour might become 'out of character': someone who normally behaves sensibly suddenly takes risks and enjoys it. Never let yourself or your friends get into this situation.

When stopping on the left, you should always be aware of pedestrians, particularly if they're close to the edge of the road. The height of your nearside mirror can vary depending on the size and type of vehicle you're driving. If in doubt, approach these situations with caution and stop if necessary.

DVSA or the police can order an immediate prohibition. The vehicle may be immobilised and you won't be able to drive it until the faults have been rectified. Details are notified to the traffic commissioner. Never use a vehicle that you know is faulty.

Never follow any road user too closely. This is particularly important when you're following scooter or motorcycle riders, or cyclists. They might brake or swerve suddenly; for example, to avoid a pothole on a road with a poor surface.

In very wet conditions, tyres may be unable to clear all the water from their path. This can result in a layer of water building up between the road and the tyre - a situation known as aquaplaning. To regain control, ease off the accelerator and, as the vehicle slows, the tyres should regain their grip. It's safer to reduce the risk of aquaplaning occurring by driving more slowly in very wet weather.

High-sided vehicles are severely affected by side wind because of the large surface area of the bodywork. The risk of loss of control is increased if the vehicle is unladen.

The cyclist may not be able to get into a right-hand lane due to heavy traffic. Give them room, as they may not be taking the exit you expect.

Whenever possible, call the emergency services first. If you're able to give first aid, remember DR ABC. Check for Danger, then check the casualty for a Response. Check the Airway, and try to establish Breathing by gently lifting the chin up and forward. Give Compressions if necessary. Try to stop any severe bleeding. If you feel you aren't capable of carrying out first aid, consider taking some training. It could save a life.

Be aware of, and obey, all speed limits. On a motorway, any lorry that's articulated, towing a trailer, or over 7.5 tonnes mustn't exceed 60 mph (96 km/h).

You should take precautions against dropping mud on the road, because it's a hazard to other road users. It's also an offence for which you could be prosecuted.

Research shows that approximately 40% of SRVIs involve commercial vehicles. The consequences are usually very serious because of the size of the vehicle and the fact that there is no braking before the impact.

Emergency refuge areas may be found next to the hard shoulder on a smart motorway. If possible, you should use one of these areas, rather than the hard shoulder, when you break down. If the hard shoulder is being used as a running lane, take care when you rejoin the motorway.

At the scene of an incident, the first priority is to prevent any further collisions by warning traffic. You can warn other traffic by switching on hazard warning lights or displaying an advance warning triangle, or by any other appropriate means.

Suspension faults may result in road damage. Road-friendly suspension reduces the impact on the environment, the road surface and under-road services.

The handling of a six-wheeled bus or coach is not much different from that of a two-axle vehicle, except that punctures can be more difficult to detect.

The longer top deck needs a wider turning circle than the cab below it. To avoid hitting lampposts, telegraph poles, etc, you must allow for this overhang when turning.