Lane changing on dual carriageways:
Should be done smoothly and gradually with at least 4 flashes of the indicator before you start the move. Use the door mirror and a sideways glance to check alongside before moving. The move across lanes should be done with no discernable movement of the steering wheel, just a gentle drift. It should take about 5 seconds to complete and is usually achieved by using acceleration (except when there is slowing traffic in front of you).
In light traffic indicate when there is a gap, and try to keep ahead of any vehicle already in the lane you want.
In heavy traffic check the mirrors and indicate for what you think may be a possible gap. The best time to indicate would generally be when the car you want to come out behind of, is next to you. Then if you get a reaction from the following vehicle, you can begin your move across. If this doesn't work out, don't cancel the indicator, but leave it on, and wait to see if someone else will let you across.
If you are doubtful as the whether the car behind on your right is going to let you across - Accelerate in your lane to change position relative to the following vehicle. If you can distance yourself from them then you know it is safe to move across.
Always glance sideways before changing lanes – the blind-spot on 3 lane sections is very large and could hide a bus. Never change 2 lanes at once – always do them one at a time.