Don't use your turn signal if you are only using it right when you change lanes. The point of a turn signal is to warn people that you are about the change lanes so they have time to react. Don't accelerate when some one signals that they are going to come into your lane. You are only encouraging the problem I explained in the first paragraph. Finally, if you signal to change lanes and some one accelerates to prevent you from changing lanes, tail them and lay on your horn until they get out of your way. This works for me, but it takes a few minutes of laying on my horn sometimes. When people do bastardly things on the road, their justification is always obliviousness... oh sorry, I didn't see you there - type of attitude. By laying on your horn for a long time, you make the fact that they did something wrong so obvious that the person can no longer lie to themselves about being oblivious, so they move out of your way.