Right of Way?

What is the name of your state? Pennsylvania

Two cars are driving the same direction on a two lane street. The car in the right lane decides to change lanes and begins to edge over. The driver in the left lane choses not to acknowledge the other car or make room for it to merge. The driver in the right lane continues moving over in an effort to force an opening. The drive on the left continues to ignore the efforts of the other driver. A collission occurs. Who is at fault? The driver in the right lane for driving into the car in the left lane, or the driver in the left lane for not yeilding to the driver in the right lane? Does the answer change if there are other factors, such as the driver in the right lane did not use a turn signal or the driver in the right was forced to change lanes due to a lane closure or an obstruction in the road? I frequently find myself on both sides of this situation (minus the collision, of course) and I've wondered what exactly the rules are governing a driver's actions. If anyone knows, I would love to hear the answer.

[Bravo8]

Insurance companies are responsible for determining fault in collisions.

However, the driver attempting to merge would be in violation of a number of statutes. The other driver would not be in violation, provided they did not speed up in an attempt to prevent the other driver from merging (and even then it would be a stretch).