DUAL-CARRIAGEWAYS

Dual carriageways often have higher speed limits than other roads.

To allow for this faster-moving traffic, dual carriageways have two or more lanes in each direction.

Traffic moving in opposite directions is separated by a central reservation; this sometimes has a crash barrier to protect the streams of traffic from one another.

Most dual carriageways are clearways (but not all clearways are dual carriageways). Clearways are roads on which you are not allowed to stop; stationary vehicles would pose extreme danger to fast-moving traffic.

Although the average speed on dual carriageways is higher than on other roads (with the possible exception of motorways) you will still have to to deal with hazards that you find on smaller two-way roads, such as cyclists, slow vehicles, traffic lights, crossroads, side turnings, gateways, etc.

This means that you must exercise special care, especially when joining and leaving dual carriageways.

Joining dual carriageways

Although there are many conventional T-junctions and crossroads on dual carriageways, motorway-type slip roads are becoming more common.

When entering a dual-carriageway from a slip road you will use the acceleration lane.

The acceleration lane is an extra lane on the left for use when building up your speed before merging with traffic on a dual carriageway so that you can join the flow safely.

The routine that you will use to join the flow of traffic on the main carriageway is the same as that you will use when joining motorways after you have passed your test, but remember, there are extra hazards to look out for when joining a dual carriageway - be especially careful to watch for cyclists; on dual carriageways in town, keep a lookout for pedestrians.

The routine for joining from a slip road is:

Mirrors and signal

Even though it should be obvious to other drivers that you are intending to pull out, a signal is useful because not everybody is as alert as they should be.

The picture above shows how NOT to do it! The truck driver is pulling out without signalling.

Watch for a gap

You need to assess the traffic as early as possible as you approach and look for a safe gap

Once you have identified the gap, concentrate on the car that you are going to follow.

Adjust your speed

Use the slip road and acceleration lane to adjust your speed so it matches the traffic in lane (the lane-one of the dual carriageway (the lane that you will be moving into).

Too fast and you risk getting too close to the cat ahead; too slow and you will inconvenience following traffic.

Joining

Just before moving into position in lane-one it might be necessary to have a quick glance over your right shoulder.

There is a possibility that a vehicle may be hidden in your blind spot. But be careful - this is just a QUICK GLANCE.

You might be travelling as fast as 70 mph, this is approximately 33 metres per second - you need to look where you are going!

Look for speed limit signs, on a dual carriageway the National Speed Limit sign means a maximum of 70 mph.

Remember the basic rule for 'emerging' - only pull out if you are sure that it is safe and that you will not inconvenience other drivers.

Joining at T junctions or crossroads

If you join a fast dual carriageway from a T-junction take extra care when judging the speed of traffic already on the main road. You will need quite a while to build up your speed from a stand still, this means that you will need a much bigger gap than on slower, two-way roads.

Some left turns will have acceleration lanes, use the procedure described above for a slip road if this is the case.

If you are turning right into a dual carriageway, wait until both sides are clear unless there is a large gap in the central reserve. If the gap in the centre is large enough, you can treat each carriageway as a separate road.

The car in the diagram right would not be able to wait safely in the central gap. Although it could probably fit into the gap if it positioned at a slight angle, it would obstruct the road for any traffic that wanted to leave the dual carriageway. The vehicles in the picture below show how much space you need to wait in the centre.

Leaving dual carriageways

At some dual carriageways you will leave via a deceleration lane and an exit slip road, at others there will simply be a regular junction or perhaps a roundabout. However the exit road is configured you will need to act much sooner than you would on slower two-way roads to allow for the higher traffic speeds.

Deceleration lanes are found on exit slip roads; they allow you to slow down without holding up following traffic on the main carriageway.

Usually, you shouldn’t need to start braking until you enter the deceleration lane.

However you leave a dual carriageway always complete your 'mirror in the new road' safety check to complete the manoeuvre.

The routine for leaving via a slip road is:

Mirrors

Check your mirrors early, moving into the left hand lane about half a mile before your exit if you are overtaking.

Signal

On fast dual carriageways you will need to signal left much earlier than you would on other roads. Other drivers need plenty of warning about your intention to turn off. Where there are countdown markers, signal at the three hundred yard marker (the one with three white bars) and maintain the signal until you have left the main carriageway. You might need to signal again if the slip road terminates at a roundabout or other junction - if this is the case you need to go through the full MSM routine again.

Position

Maintain speed and position (normal left lane position) until you reach the start of the deceleration lane. Check your mirrors again (all mirrors) and then move to the left to enter the deceleration lane. It might be necessary to ease off the gas before joining the deceleration lane, however, unless the lane is particularly short, it shouldn't be necessary to use the brakes yet. If drivers behind ate not responding to your signal a gentle touch on the brake pedal to activate the brake lights might be useful.

Speed

After joining the deceleration lane, use your brakes to slow down. If you have been driving for a while at high speed, check your speedo - you might be going faster than you think.After a period of driving at a consistent high speed, 50 mph can feel like 30 mph.. The routine for leaving via a left turn is:

Use MSPSL routine as normal.

Give plenty of warning to following vehicles on faster roads.

The routine for leaving via a right turn is:

Mirrors

Check your mirrors early, moving into the right hand lane about a quarter of a mile before your exit

Signal

Signal before moving to the right hand lane, remembering that other drivers need plenty of warning about your intentions on fast roads

. Maintain your signal after changing lanes, others will need to know why you are in the right hand lane

Position

Move to the right hand lane early as described above. Sometimes there will be designated right turn lane (see the diagram

Speed

As with a left turn, your speed must be slow enough to turn safely, or to stop if their is an obstruction in the side road.

Remember the following vehicles - if another vehicle is following much too closely, you may have to slow down a bit extra on approach to give the driver behind time to react when you turn.

Take special care when judging the speed of approaching traffic.

Remember that you have two lanes to cross and that traffic will often be approaching faster than on two-way roads. With this in mind the 'walk across rule' may not give you enough time.

Breakdowns

A breakdown on any road can cause problems, but these become more acute on dual carriageways, especially if there is no hard shoulder.

If you suspect that there might be something wrong with your car, pull off the road at the first possible opportunity and seek help.

Because some journeys on dual-carriageways involve high-speed driving for along distance, your vehicle is subject to more stress and strain, this could make a breakdown more likely if there are any problems.

If you break down take the following precautions:

 If possible move your car off the main carriageway and on to the hard shoulder or into a lay-by.

 If there is no hard shoulder, try to move your vehicle onto the verge but be careful in summer - your hot exhaust pipe could set fire to dry grass. If you cannot move your vehicle do everything you can to make it as conspicuous as possible.

 Switch on your hazard warning lights and use a warning triangle to warn other drivers.

 As soon as you car is in a safe place, telephone for help. If your car is in position where it might endanger others, contact the police.

 It is usually safer for passengers to wait on the grass verge or behind a crash barrier.  Animals should be left in the car unless you are 100% sure that they are under full control and securely restrained (e.g., dogs should be kept on a secure lead).