Rear Ended

What is the name of your state? NY
I was in a left turn only lane awaiting clearance for about 20 seconds. As I was about to make my turn, I was rear ended by a commercial vehicle, he was an employee for a car dealership The guy even admited to my husband that this was the second accident he was involved in that week. He said the first one was when he had not yeilded at a stop sign..This was in July of 2002. He of course told the police that I had made a sudden stop, which was not true. I know that it is just his word against mine. My problem now is that the vehicles insurance co. wants to pay for only 80% claiming that NY has a partial to blame law. I dont think that I should be liable for anything. I know that I was waiting there for some time before he came about, but for arguements sake lets say it was as he claims..that would still have made him in the wrong, because he should not be that close to the vehicle. The estimate that they offered is way to low. I took it to a body shop that deals with insurance co.'s and he agrees. What can I do? Is there such a law that they claim in NYS?
Thanking you in advance for your repy...
Eve,,