It's illegal to drive a vehicle that's emitting excessive exhaust smoke, so you should get the problem fixed as soon as you're aware of it. Excessive exhaust smoke increases pollution and creates a hazard for other road users.

If you can't produce your driving licence when asked to do so by a police officer, you may be asked to produce it at a police station within a certain time.

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.

If you're approaching a set of traffic lights and you can see they've been on green for a while, be prepared for them to change. Ease off the accelerator and be ready to come to a gradual stop if you need to. Don't try to beat the red light; it may change as you come closer, causing you to brake late and harshly. Think of your passengers.

Giving wrong signals causes uncertainty and confusion to other road users. Only give signals that are relevant and timed to match your actions.

All physical contact with children should be avoided except in specific circumstances such as genuine self-defence, a medical emergency, or to prevent a serious offence or threat to anyone's safety.

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.

While overtaking, you'll need to judge carefully when to return to the nearside lane. Check your left-hand (nearside) mirror to make sure the rear of your vehicle is well clear. You should allow for the length of both vehicles and take into account the speed difference. Don't cut in too soon on the vehicle you've overtaken, and don't rely on signals from other drivers; they may be signalling to someone else.

When refitting a wheel, the nuts should be tightened to the correct torque. They should be rechecked after about 30 minutes if the vehicle hasn't moved, or after 40 to 80 km (25 to 50 miles) of driving.

Red Routes operate in many busy cities and are designed to ensure the route has no obstructions to cause delays during peak periods. Road signs and red road markings identify roads where Red Route waiting and loading restrictions apply.

Driving slowly will give you better control of your vehicle. By using a high gear, you reduce the chance of your wheels spinning and skidding on the snow.

Once you have a secure hold on the object, keep your head up and bend your knees.

An illness that could affect you while you're driving, such as a heart condition, may make it unsafe for you to drive. You must tell DVLA if you develop any serious illness or disability that's likely to last more than three months and that could affect your driving. Partial blindness and mental disorders can also prevent you from getting a driving licence for large vehicles.

If you're travelling in heavy rain, you should be aware that it could take twice as long for you to stop as it would in dry weather. Increase your distance from the vehicle in front to allow for the longer stopping distance.

All drivers may use hazard warning lights to warn other road users of danger on specific occasions. When you're driving a school bus, you may also use these lights when you've stopped and children are getting on or off the bus.

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

You may be driving in the rush hour, when traffic is heavy, so when you stop you're permitted to show your hazard warning lights. This will tell other road users that children are getting on and off the bus. Look out for passing traffic and make sure that all your passengers get on and off safely.

Always indicate your intentions in good time; this will allow others time to alter their speed and course if necessary. Always check your blind spots before changing lanes.

Before you make a turn or a change of direction, however slight, you should always check the mirrors. If you intend to turn left, check your left-hand (nearside) mirror first.

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

When you're being overtaken, the other driver has to decide when it's safe to complete the manoeuvre. Don't give an unofficial signal, however well intended. There may be a hazard you're unable to see from your position.

Always be aware of your limited vision around your vehicle, due to its size and shape. Never move off without checking along the nearside of your vehicle. You should be aware of the possibility of cyclists and motorcyclists getting trapped between your vehicle and the kerb.

Never drive after taking drugs you don't know about. They might affect your judgement and perception - and, therefore, endanger lives.

You can legally remove your seat belt when carrying out a manoeuvre that involves reversing. Don't forget to put it back on again when you've finished.

Buffer lanes are often found in places that are frequently subjected to high winds. Examples include high-level bridges, high-level roads, exposed viaducts and exposed stretches of motorway. Listen to the weather forecast, which should tell you of any need to re-plan your route.

This sign gives a clear instruction. You should prepare to negotiate a left-hand turn.