Changing lanes can be a dangerous manoeuvre if not done properly. Remember when practising to change lanes start with low risk areas for example quiet multi lane low speed roads, be use to checking your rear vision mirror and knowing what vehicles are around you and there distance relevant to your vehicle, have good vision and a sense of distance to what is in front of you, so you no how much time you have to check your mirrors. when you make the decision that it is safe to change lanes indicate check relevant mirrors, shoulder check and merge gradually into lane, do not steer quickly especially at high speeds and do not reduce speed unless it is to go behind the vehicle beside you or the traffic flow is reducing speed. Lane changers can be done safely and easily if a constant knowledge is kept of what is around you. if it cant be done safely don't do it.