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Dual carriageways

The term dual carriageway simply means a road where lanes in one direction are separated from lanes on other directions by central reservation. There may be safety barrier along this central reservation.
Some dual carriageways are similar to motorways with slip roads to join and leave. However, motorway regulations do not apply

Each side of the dual carriageway can have a number of lanes (typically two or three). Keep to the left-hand lane unless signs or road markings indicate otherwise or unless you are overtaking.

Driving on this type of road requires particular skills:

  • Judgment and planning  well ahead
  • Joining and leaving dual carriageways
  • Safe separation distance
  • Effective use of mirrors
  • Lane discipline
  • Overtaking

Joining dual carriageways

There are a few ways you can join a dual carriageway:
From a slip road

When entering a dual-carriageway from a slip road you will use the 'acceleration lane’. The slip road 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. Don't take for granted that traffic already on the dual carriageway will make space for you. Always be prepared to use the full length of the slip road and, if you have to stop and wait at the end of the slip road before pulling out when safe to do so.
To join a dual carriageway from a slip road use MSPSL routine on approach


From a junction emerging Left or Right

Emerging Left If there’s no slip road; emerge as you would to turn left into a major road. If there is a slip road, emerge as you would to join a motorway

  • Adjust you speed  to that of traffic on the main carriageway.
  • Look for a gap in traffic and move into the left -hand lane.
  • A quick sideways glance might be necessary to check the position of other vehicles.
  • Stay in the left lane-hand lane until you get used to the speed of the traffic in the other lanes.
  • Don’t emerge unless you are sure you won’t cause traffic to change speed or direction.

Emerging Right into a dual-carriageway,  wait until both sides are clear unless there is a large gap in the central reserve area. If the gap in the centre is large enough, you can treat each carriageway as a separate road. 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 is safe and then wait for a gap in the traffic on the second carriageway. If the central reservation can’t contain the length of your vehicle, you must not 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 change speed or direction.

As a two-way road becomes a dual carriageway.

Look out for the sign where you have a dual carriageway ahead and be aware of a likely change in speed limit. Check Mirrors well before changing speed suitable for new road.


Driving on dual carriageways


Lane Discipline

Using the lanes properly is an important part of safe driving, the basic rule is to use the left-hand lane unless you are overtaking, turning right or road signs and markings direct you otherwise.

Drive in the middle of your lane - Don’t ‘straddle lanes
Keep to the left hand lane wherever possible
Position yourself in good time
Follow signs and road markings
Plan ahead and select correct lane in good time
Choose the correct lane for your exit ASAP


The rules about overtaking are the same as for other roads, you should normally overtake only on the right, but if traffic is moving slowly in queues, than it is safer to keep peace with traffic in your lane if this means you’re overtaking on your right, you should never move to a lane on the left to overtake.

Before you start to overtake follow the routine MPSL-MSM

Mirrors - Check your mirrors to assess the speed and position of the traffic behind.
Position – Maintain a safe distance behind the vehicle in front  so you can get good view of the road ahead.
Speed – Select the appropriate gear to make sure you can accelerate quickly enough to overtake.
Look – Assess the whole situation.
Mirrors –Check the mirrors one more time to make sure it’s safe.
Signal – Signal well before you start to overtake.
Manoeuvre – if safe change lanes gradually.

Safe separation distance

 Leaving enough distance between you and the vehicle in front is one of the most important steps any driver can take to reduce the risk of accidents. Keep a safe following distance by applying the two second rule.
"Only a fool would break the two second rule".
Two second rule is a rule we use to maintain a safe following distance at least 2 seconds behind any vehicle that is directly in front of you. For example: As the car in front of you goes past any stationary object like (bridge, road sign, lamp post) say to yourself “ One thousand , two thousand” This takes about two second to say. If you go and past the same point before you finish than you’re too close.

2 second rule

Speed Limits

The speed limits on dual carriageways will depend on their location and the amount of traffic they have to deal with. Generally in non-urban areas the maximum speed limit is 70mph. However this limit may be set at a lower level if it is in a built up area - so take notice of the road signs.

Exiting the dual carriageway

To there are three ways of exiting a dual carriageway:

  • Turning Left from a dual carriageway
  • Turning Right from a dual carriageway
  • End of dual carriageway

Turning Left from a dual carriageways

Using a slip road - Exiting the carriageway, on most carriageways you will get a sign for your exit giving you at least half a miles notice.
The countdown markers are placed at 300yds - 200yds - 100yds before your exit slip road. Start your MSPSL as you approach 300yds marker.

Exit signs

No slip road - Use the same procedure as if turning left into a minor road.

 Turning Right from a dual carriageways

In order to turn right from a dual carriageway plan well ahead by observing road signs and lane markings as this will help you to get into right hand lane early, signal much earlier than you would on an ordinary road, if there is a deceleration lane move into it.
Sometimes at the junction the central reservation has gaps for turning right, wait in the gap until a safe gap appears in traffic. When it is safe complete your turn and move into left-hand lane of the road you are entering.

End of dual carriageway

Watch out for the ‘end of dual-carriageway’ warning sign. Don’t start to overtake after you see the sign, otherwise you might run out of road or even worse, find yourself facing an oncoming vehicle head on!

end of dualcarriagway

Pass Plus
Maximum Speed Limit
National Speed Lmit
Give Way
End of Road Works