Joining a Motorway

Using a slip road

You join a motorway from a roundabout or a main road by using a slip road.

The procedure here is the same as for when joining a dual carriageway. Slip road leads to an acceleration lane.

acceleration lane

The rule here is not to interfere with the traffic already on the motorway. Make sure your speed is the same as the traffic already on the motorway. You should accelerate as you drive along the slip road.

Merging the traffic

Vehicles already on the motorway usually realise you need to join the main carriageway and they try and move over to the other lane (this is not always possible if the traffic is busy). This makes room for you to join the first lane of the motorway.

Merging the traffic

Try to avoid stopping at the end of the slip road unless queuing to join other slow-moving traffic.

slow-moving traffic

Generally the traffic will move to make space for you but be prepared to slow down if you need to.

Some slip roads continue as a dedicated lane, so you will not have to join the motorway as described above. Signs and road markings will indicate if this is the case.

slip roads

Mirrors and signals

Follow the usual 'mirror-signal-manoeuvre' procedure to find an appropriate gap in the moving traffic.


Mirrors and signals must be used correctly to avoid interfering with the following traffic. Full and proper observation as you enter usually involves looking over your right shoulder as well as using your door mirrors. Don't rely on mirrors alone. You may need to look over your right shoulder to verify the position of other vehicles.

The main points to remember

  • adjust your speed to match that of the traffic already on the motorway
  • indicate to show your intention to join the motorway
  • give priority to traffic already on the motorway
  • join where there's a suitable gap in the left-hand lane
  • use the MSM/PSL routine
  • don't force your way into the traffic stream
  • don't drive along the hard shoulder