Air deflectors reduce wind resistance by streamlining the vehicle. They're most effective when there's a headwind. The streamlining also reduces the vehicle's fuel consumption.

When overtaking with a long vehicle, it's very important to be aware of the position of the road user you're passing. Check the nearside mirror to make sure you've passed safely before returning to the left. Be especially careful when overtaking motorcyclists, as they may be affected by the draught from your vehicle.

Before uncoupling a trailer, always make sure that you've parked on firm, level ground and applied the trailer parking brake.

When you're stationary for any length of time (for example, in a traffic jam), switch off your engine. This will cut exhaust emissions and so help to protect the environment.

When diesel fuel spills onto the road, it makes the road surface extremely slippery. This can cause danger for all types of vehicle, but particularly for those with two wheels, which rely on their tyres' grip to remain upright.

Your vehicle will handle very differently when it's full, compared with when it's empty. Having 75 passengers on board would increase the weight of the bus by about 5 tonnes - and the passengers may also have luggage. It will take longer to build up speed and the vehicle will be more difficult to stop. Forward planning and controlled braking will be required to allow for this extra weight.

Double red lines indicate that you're on a Red Route and in a no-stopping area. Red Routes also have single red lines, with signs showing the times that restrictions are in force. There are also parking and loading boxes, which have signs explaining the restrictions that apply.

When there's no traffic ahead of you, you should always drive in the left-hand lane.

If it's possible, and you can do so without causing further danger, it's safer to drive a vehicle that's on fire out of a tunnel. The greatest danger in a tunnel fire is smoke and suffocation.

In slow-moving traffic, particularly on dual carriageways or motorways, always be on the lookout for motorcyclists who approach from behind and filter through narrow gaps between vehicles.

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.

Local-authority environmental health departments check vehicles' exhaust emissions. They have the power to prosecute the driver and the operator, as do enforcement bodies such as DVSA.

Newer buses and coaches have marker lights along the side; these ensure that they're visible as they emerge at junctions, roundabouts and in other situations. If your vehicle has marker lights fitted, they must all be clean and working.

Staying well behind the vehicle in front will improve your view of the road ahead. This will give you more time and room to react to hazards. Use the two-second rule to make sure you're not too close. Don't move out to the right, as this could put you into the path of an oncoming vehicle or obstruct smaller vehicles that wish to overtake.

The only time you may use hazard warning lights while driving is when you're on an unrestricted dual carriageway or motorway and you want to warn other drivers of a hazard or obstruction ahead. Only use them for long enough to make sure your warning is seen.

The Driver CPC qualification and training syllabus is designed to lead to enhanced professionalism and improvements in road safety. Other expected benefits are a general reduction in fuel consumption and emissions, resulting from a better knowledge of fuel-efficient driving techniques.

When making a left turn with a long vehicle, you may have to adopt an unusual position, well over to the centre of the road. Always signal your intentions in good time, and make good use of the mirrors, especially the left-hand one. Be alert for less experienced road users putting themselves in danger by coming up on your nearside.

Signal if necessary and move back to the left as soon as it's safe to do so. Don't drive for long distances in the centre or right-hand lane unnecessarily.

The smallest lapse in concentration can result in loss of control. Even when your tachograph would allow you to drive for longer, stop somewhere safe and rest if you feel your driving may be affected by your tiredness.

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.

Under no circumstances should you drive with your passenger door open. An open door invites people to make rash decisions to enter or leave the vehicle as you're about to move away; this can be extremely dangerous.

As you approach the children, consider whether you need to sound the horn as a warning. Always check your nearside mirror as you pass any hazards on the left, so that you know when your vehicle is clear of the hazard.

Try to anticipate the actions of other road users. When you're waiting at a junction, don't emerge until you're sure of their intentions; their signals might be misleading.

When an ambulance is displaying a flashing blue light, try to stop in a safe place to allow it to pass. Make sure you don't endanger any other road users or commit an offence; for example, by driving past a red traffic light.

When passing other road users - especially motorcyclists and cyclists - in wet weather, the spray from your vehicle could affect their control. Leave plenty of room as you pass, and look in your left-hand mirror to check that they're still in control.

Take care if you're driving an empty high-sided vehicle when it's windy. Watch for places where the conditions could suddenly change, such as a gap between buildings or when passing under a bridge. Reduce your speed and stay alert for other road users who are also affected by these weather conditions.

The importation of illegal immigrants into the UK carries heavy penalties. A fine of up to £2000 can be imposed for each illegal immigrant. This fine can be imposed on each 'responsible person', which includes the vehicle owner, hirer and driver.

Bus-lane signs show the vehicles allowed to use the lane and its times of operation. Where no times are shown, the bus lane is in operation 24 hours a day.