These multi-lane and mainly high speed roads which have a central reservation/barrier separating the two carriageways. There are three ways of joining a dual carriageway:
Your road may simply turn into a dual carriageway aheadYou may need to join via a slip roadYou may need to emerge directly onto a dual carriageway
Emerging - Your road turning into 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 your mirrors well before changing speed suitable for new road.
Emerging from a slip road
Take a note of the speed limit that applies for dual carriageways and use the slip road (also known as an acceleration lane) to build up speed to that of the traffic on the dual carriageway to make it easier to join. If the dual carriageway is not particularly busy then most traffic will travel at the maximum speed - make use of your lower gears to build up speed quickly.
Look for a gap in the traffic and move into the left hand lane applying the M-S-M routine (always apply a right signal in good time before emerging). Try not to look too far round over your shoulder when emerging as regular looks in the mirrors with perhaps a quick glance for blind spot will be enough to be sure it's safe to join the carriageway. You should aim to emerge without causing traffic on the carriageway to alter speed or direction.
After you have joined the carriageway
Check your mirrorsCancel signalKeep in the left lane - until you have had time to assess the traffic and conditions on the carriagewayMake good progress
Emerging directly onto dual carriageway
To turn left Where there is no slip road you would need to emerge as you would to turn left onto a major road - take into account the speed limit on the dual carriageway to help judge a safe gap as traffic may be approaching very fast (you must join where to do so would not cause them to change speed or direction).
To turn right When joining a dual carriageway to take a right turn you will need to cross the first carriageway before you can join the carriageway you want. This is easiest where the central reservation is deep enough to have room to protect the full length of your vehicle to enable you to emerge from one carriageway at a time. Where there is not enough room you would need to be extra careful and turn right when both carriageways have a safe enough gap for you to drive across safely.
Making progress on the dual carriageway
Where there is a specific speed limit i.e. if it was a 70mph limit then if the road was clear and the weather conditions were good then that speed would be perfectly appropriate. Where the dual carriageway has a national speed limit the maximum speed will be 70mph but the road may not be safe to drive at the maximum due to bends etc. so judge your speed accordingly.
Keep a safe following distance by applying the two second rule:- "Only a fool would break the two second rule". Increase this in poor weather. You should normally stay in the left hand lane for overtaking, allowing traffic to join carriageway or turning right. To make good progress you should overtake slow moving traffic when you are sure you can do so safely.
M-S-M routine - preparing to overtake
Mirrors - always assess the speed and position of traffic behind (someone could easily be about to overtake you). You will need to check the interior mirror and the right hand/offside door mirror.
Signal - at this stage because we are only preparing to overtake do not apply signal.
Position - keep well back (apply the two second rule for a safe following distance). This will allow the vehicle in front to see you as well as keeping a safe distance.
Speed - keep to the same speed as the vehicle ahead and consider changing down a gear for extra power to help pass briskly when you get the chance.
Look - assess the whole situation
the road conditionsthe intentions of the driver aheadany hazards (look out for signs)
As the situation can change you may need to keep following the above routine until you are 100% happy it is safe to overtake.
M-S-M routine - when you overtake
Mirrors - re-assess the situation behind as well as interior and right door mirror. As you are about to overtake have a quick look for any blind spots - just a quick sideways glance (in case someone is in the process of overtaking you).
Signal - always apply a signal when going to overtake as this will help drivers behind and the person you are overtaking.
Manoeuvre - pull out on a smooth line overtaking as quickly as you can. Checking mirrors to make sure you are clear of the vehicle you are overtaking so that you do not cut them up. Apply a left signal and steer back gradually to the left lane unless you have other slow moving traffic, in which case pass them before moving back to the left lane.
Dealing with traffic joining the dual carriageway
You must look out for traffic that wants to join the carriageway so that you can be prepared to help them join. The main areas where you can expect traffic to join would be:
As you approach slip roadsWhere there are junctionsOut of garagesPulling out from parking areas
You will have three options to help traffic join:
Moving out of the left laneSpeeding upSlowing down
The best option is to move out of the left lane. Therefore, you should be checking your mirrors well before approaching the areas where traffic may want to join, in order to be confident it is safe to switch lane.
Exiting the dual carriageway
On most 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.
These countdown markers are placed at 300yds (270m) - 200yds (180m) - 100yds (90m) up to your slip road for exit. You can use these as a guide for starting the M-S-M routine.
Look out for any signs that warn you of a sharp bend or change of direction to ensure you get your speed down in time and select the correct gear. Try not to slow down unnecessarily on the carriageway unless your mirrors show traffic is far away in the distance. Use the slip road to reduce your speed and be careful you do not travel too fast on the new road.