Lesson 1, Topic 1
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Dual Carriageways

What is a Dual Carriageway?

A Dual Carriageway is a road where a central reservation separates lanes going in one direction from the lanes going in the other direction.

You can enter a Dual Carriageway in a few different ways:

  • Your road may just turn into a dual carriageway ahead
  • You may join by using a slip road
  • You may join by emerging from a junction
  • You may join by emerging from a roundabout


This picture shows that traffic going up the road, and traffic going down the road, are separated by a grass and a barrier.

Screen Shot 2020-07-24 at 14.57.19

Entering a Dual Carriageway


The aim of a slip road (acceleration lane) is for vehicles to pick up speed to match the speed of the traffic already on the dual carriageway.

How to Use a Slip Road

  • Check the speed limit for the road you are entering
  • Check middle and right door mirrors
  • Increase your speed to match the speed of the traffic already on the dual carriageway
  • You may change into a lower gear to help pick up speed
  • Look for traffic already on the dual carriageway and plan where you will join
  • Half-way down the slip road, indicate right
  • Use the whole of the slip road
  • Before emerging, check your right door mirror
  • Once you are on the dual carriageway, check your mirrors
  • Stay in the left lane until you become accustomed to driving at speed


Turning Left

If there is no slip road, you will emerge in the same way as if you are turning onto a road.

  • Look for a big enough gap, so you can emerge without causing other road users to slow down
  • Once you emerge, increase speed rapidly
  • Check your mirrors
  • Stay in the left lane until you become accustomed to the speed

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Turning Right 

To turn right you will need to  cross the first carriageway before you can join the carriageway you want.

You need to assess the width of the central reservation. Is it wide enough to fit your vehicle?

If it is, you can head for the central reservation first. Then make a decision about when to turn into the new road.

If it isn’t, you need to take extra care to ensure that there is a big enough gap in traffic on both sides of the carriageway for you to drive across safely.


You can enter some dual carriageways using a roundabouts. You have already covered roundabouts in your lessons. Make sure you check your mirrors and pick up speed immediately.

Stay in the left hand lane until you are accustomed to the speed.

Driving on a Dual Carriageway


You should drive in the left hand lane, less you are overtaking.

Once you have passed the slower moving vehicle, move back to the left lane.

Aim to drive in the centre of your lane.

Dealing with Traffic Joining

Look well ahead for slip roads entering the dual carriageway.

Plan to help others road users to merge, although remember that you have priority.

You can help them to merge by:

  • changing lane – check mirrors and ‘on the move’ blind spot first (see below), then signal and gradually change lane.


  • speeding up – increase your speed to get slightly ahead of the vehicle
  • slowing down – decrease your speed slightly if the vehicle is trying to get in front of you and you cannot change lane


You MUST NOT overtake on the left, unless the traffic in the right-hand lane is congested and the traffic in the left-hand lane is moving faster.

Changing Lane on a Dual Carriageways

Changing lane on a dual carriageway is potentially very hazardous.

Making all the relevant checks first will make it a safe and comfortable move though:

  1. Mirrors – middle and right
  2. Signal – if it’s safe
  3. Mirrors – middle and right
  4. Look – ‘on the move’ blind spot
  5. Drift – look at the lane you want to move in to

Once you are in the new lane, check your middle mirro


  • Before changing lane you may go into a lower gear. This will enable you to pick up speed quickly.
  • ‘On the move’ blind spot means a CHIN to SHOULDER check – turn your head as far as your chin touching your shoulder to look out of your side window

Use the same routine to move back to the left-hand lane.

NOTES: make sure you can see the vehicle you are passing in both mirrors before moving back to the left lane


Reflective Studs

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Knowing where the different coloured studs are, can help keep you safe if you cannot see the road clearly due to poor weather.

  • White studs are between the lanes
  • Red studs are between the left lane and the hard shoulder
  • Amber studs are between the right lane and the central reservation
  • Green studs are between the left lane and slip roads

Signs and Road Markings

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Dual carriageway ahead

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Countdown Markers

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End of dual carriageway

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National Speed limit

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Traffic merging from left

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A Note on Driving at Speed

The faster you drive in a car, the less you need to turn the steering wheel.

If you are driving at 60 – 70 mph, steer very slightly and gently.

Entering a Dual Carriageway with a Short Slip Road

Slip roads are often long, to give vehicles enough time to accelerate to get up to the speed of the traffic already on the dual carriageway.

Some slip roads are very short which make it harder to enter at speed.

You may need to wait at the start of a slip road for a long enough gap to accelerate into.


Exiting a Dual Carriageway

To exit a dual carriageway:

  • Look for your exit and get in the left lane in good time
  • Start to signal at the 3rd countdown marker
  • Check your right door mirror in case a vehicle in the next lane is trying to exit
  • Use the whole of the slip road
  • Check your speedometer – you might be driving faster than you think

Attempts for Clip 1

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