On a dual carriageway, lanes in one direction are separated from lanes in the other direction by a central reservation. There may be a safety barrier along this central reservation.

Some dual carriageways are very similar to motorways, with slip roads to join and leave. However, motorway regulations don’t apply and you may come across slow-moving traffic such as cyclists or farm tractors.

Emerging from a side road

To turn left

If there’s no slip road, emerge as you would to turn left on to a major road (see the advice earlier in this section). If there’s a slip road

Use the slip road to adjust your speed to that of traffic on the main carriageway.
Look for a gap in the traffic and then move into the left-hand lane.
A quick sideways glance might be necessary to check the position of other vehicles.
Stay in the left-hand lane until you get used to the speed of the traffic in the other lanes.
Don’t emerge unless you’re sure you won’t cause traffic to alter speed or course.

To turn right

You need to cross the first carriageway before you can join the carriageway you want.

Assess whether the central reservation is deep enough to protect the full length of your vehicle.
If the central reservation is deep enough, cross the first carriageway when it’s safe and then wait within the central reservation for a gap in the traffic on the second carriageway.
If the central reservation can’t contain the length of your vehicle, you mustn’t begin to cross until the dual carriageway is clear in both directions.
Don’t emerge unless you’re sure you won’t cause traffic on the major road to alter speed or course. This is particularly important if you’re driving a longer vehicle, or towing a caravan or trailer.

Defensive driving

Watch out particularly for motorcyclists at these junctions. They can be difficult to see due to their narrow profile and their speed can be difficult to judge. They may also be hidden behind slower-moving traffic if they’re overtaking.

After you join the carriageway

Check your mirrors.
Cancel any indicator signal.
Drive in the left-hand lane.
Accelerate as soon as you can to a suitable and safe speed for the new road.
Don’t overtake until you’re used to the conditions on the new road.

Always look for signs that might indicate a higher speed limit on the dual carriageway. Allow for this when you assess the speed of oncoming traffic.

Leaving a dual carriageway

Turning left from a dual carriageway If there’s no slip road, use the same procedure you would for turning left into a side road.

Use the MSM/PSL routine and get into the left-hand lane in plenty of time.
Signal left much earlier than you would on ordinary roads because of the higher speeds involved.
Reduce your speed in good time.

If there’s a slip road on the left, use the same procedure as you would for leaving a motorway (see section 11).

Turning right from a dual carriageway

The central reservation sometimes has gaps for turning right. Watch out for special approach lanes.

Use the MSM/PSL routine.
Signal right and move into the right-hand lane much earlier than you would on normal roads because of the higher speeds involved.
Observe any lane markings.
Reduce your speed in good time.

Take particular care when turning. You might have to cross the path of fast oncoming traffic in two or more lanes. If in doubt, wait.

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