This means you have to match your vehicle’s speed with the speed of the traffic on the motorway. You must give priority to the traffic already on the motorway, and you must never cross from the slip road and go directly into either the second or third lanes, stay in the first lane for a while until the traffic has adjusted, then you can make your planned move into the lanes to the right, should you need to.
Things to remember when joining the motorway:
As you drive along the motorway you will see the exit slip road, which will indicate to you the presence of other motorists wanting to join the motorway.
You can help potential traffic entering the motorway by carefully moving over from the left hand lane, to the middle lane. This will help them join more safely. If this is impossible due to heavy traffic in the other lanes, try to adjust your speed to allow the joining traffic some space. Never get into a race with them. Look well ahead and see what vehicles are joining and how they are spaced, and consider adjusting your speed.