Dual Carriageways

To know and understand how to safely join and drive on dual carriageways
To be able to safely drive on dual carriageways and understand the rules of driving on a dual carriageway.
  • To know how to join, use and leave a dual carriageway safely
  • To know the speed limits that apply to dual carriageways
  • To know how to safely overtake
  • To know when to use the left and right hand lanes
  • What to do if you breakdown on a dual carriageway
  • Weather conditions on dual carriageways
On your driving test:
On test: Dual carriageways

Assessment criteria: Due to the nature of this one it is possible for it to be marked under various different categories.


On dual carriageways, the lanes in each direction are usually separated by a central reservation. Always remember that you may come across slow moving vehicles such as tractors or cyclists. Use the slip roads to match the speed of the traffic you are joining.

Joining and Leaving a Dual Carriageway:

Emerging from a side road onto a dual carriageway.

DVSA Syllabus joining dual carriageway

Turning left if there is no slip road:

  • Emerge as you would if turning left onto a major road.

Turning left if there is a slip road:

  • Use the slip road to adjust your speed to that of other traffic
  • Look for a gap in the traffic and move into the left hand lane
  • Always check for other traffic before emerging

Always remember if you need to stop at the end of a slip road, it may then be difficult to reach a safe speed when joining the new road.

To turn right always assess the gap in the central reservation to ensure the entire length of your car will fit. If it is then:

  • Cross the first carriageway when it is safe to do so, then wait within the gap in the central reservation until it is safe to join the traffic on the second carriageway
  • Do not emerge unless you are sure you will not cause other traffic to alter speed or change lanes

If the gap in the central reservation is not large enough to wait in then you must not begin to cross until the dual carriageway is clear in both directions.

Leaving a dual carriageway.

Turning left from a dual carriageway

DVSA Syllabus Leaving a dual carriageway left

Exit signs.

On most dual carriageways you will get a sign for your exit giving you at least half a mile before the junction. Try to ensure you do not leave it too late to get into the left hand lane ready to exit.

If there is no slip road, use the same procedure as you would when turning left into a side road.


  • Use your Mirror, Signal, Manoeuvre routine
  • Get into the left hand lane in plenty of time
  • Signal left early, due to the higher speeds of traffic
  • Reduce your speed in good time

Turning right from a dual carriageway

DVSA Syllabus Turning right dual carriageway

The central reservation sometimes has gaps for turning right. These may have a special approach lane to make this safer.

Always –

  • Use your Mirror, Signal, Manoeuvre routine
  • Signal right and move into the right hand lane in plenty of time
  • Observe any lane markings
  • Reduce your speed in good time
  • Take particular care when turning as you may be crossing the path of two lanes of fast moving oncoming traffic, if in doubt always wait
Speed And Overtaking On a Dual Carriageway:

DVSA Syllabus fast traffic on dual carriageway

The National speed limit for a car on a dual carriageway is 70 mph unless otherwise stated. Other speed limits apply for cars towing caravans or trailers and for other types of vehicles. Always be prepared to encounter slow moving vehicles on a dual carriageway.

Once you have joined the carriageway, adjust your speed to keep up with the flow of traffic already on the road.

When travelling on a dual carriageway, always remember that due to increased speeds situations can change very quickly. Use your mirrors frequently to check what is happening around your car.

Overtaking on dual carriageways.

You should only ever overtake on a dual carriageway when you are sure it is safe to do so.

When driving on a dual carriageway you should drive in the left hand lane unless overtaking or turning right.

When overtaking, always follow your Mirror, Signal, Manoeuvre routine.

Always check for motorcyclists as they can approach very quickly from behind.

You must not overtake on the left, unless you are already in that lane and traffic is queued and moving slowly. You must never move into the left hand lane to overtake.

Never accelerate if you are being overtaken, let the other vehicle overtake you.

If in doubt don’t overtake. Overtaking can take longer than you think, especially if you are overtaking a large vehicle.

Breakdowns on Dual Carriageways:

DVSA Syllabus breakdown vehicle

Most dual carriageways do not have a hard shoulder. If you break down always try to get your car safely away from the road if you can. The safest places are usually on a grass verge or lay-by.

Only stop on unprotected lay-bys (those with no kerbed area between them and the road) if absolutely necessary e.g. in the case of a breakdown. Fatal incidents have occurred involving vehicles stopped at unprotected lay-bys.

If you break down on a dual carriageway always:

  • Use your hazard warning lights
  • Use your warning triangle – if safe to do so
  • Move any car passengers away from the vehicle and away from the dual carriageway – behind a safety barrier if possible
  • Go to the nearest telephone and call for assistance
  • Keep any pets safely in the car
Information Signs on Dual Carriageway:

DVSA Syllabus road signs on dual carriageway

Always look out for information signs displayed on dual carriageways. These may include:

  • Restrictions on speed limit or changes to speed limits
  • Upcoming road works
  • Bends – whereby you may need to reduce your speed
  • Road conditions – side winds, fog or slippery road surface possible
  • Upcoming junctions

Always look out for road and information signs, they are there to assist you in using the dual carriageway safely and alert you to any possible events ahead.

Weather Conditions on Dual Carriageway:

DVSA Syllabus bad weather sign on dual carriageway

Due to vehicles usually travelling at a higher speed on a dual carriageway, changing weather should always be planned for.

If it begins to rain then you should increase the space between you and the vehicle in front, as stopping distances will increase. In wet weather your car’s stopping distance may be double that of a dry road.

Spray from other vehicles – especially large vehicles, may decrease visibility and may mean that you need to lower your speed.

Watch out for high sided vehicles when windy. Especially across open ground. Be careful if you see a motorcyclist overtaking a large vehicle when windy.

Remember bridges besides being exposed and windy could also be icy.

It is important that you can drive on dual carriageways safely and with confidence. Unless overtaking or turning right you should always use the left hand lane on a dual carriageway. Always remember to use Mirror, Signal, Manoeuvre routine when joining, changing lanes or leaving.

Allow for changing weather conditions and adapt your speed and stopping distance accordingly.

Look out for slow moving traffic and remember that some vehicles may be travelling much slower then the speed limit of 70mph.

You should know how to:

  • Recognise a dual carriageway and know the speed limits for it
  • Join and leave safely
  • Overtake safely
  • Deal with breakdowns
  • Deal with the changing weather
Further Reading:
The Highway Code Rule(s): 137-138, 173, 274

Driving The Essential Skills: Section(s) 8


What’s in the driving syllabus?

Click on a topic below to get started.
Please note this syllabus should be used with a professional driving instructor.


Cockpit Drill

Safety Checks

Controls and Instruments
Moving Away and Stopping
Safe Position
Mirrors Vision and Use
Anticipation and Planning
Use of Speed
Other Traffic
Dual Carriageway
Motorway Driving
Country Roads
Pedestrian Crossings
Turning the Vehicle Around
Emergency Stop
Independent Drive
Fuel-Efficient Driving
Passengers and Loads