If you feel your Insurance Company is not offering you a fair value for your vehicle!
You have the right to go to arbitration. In http://www.arbitrationappraisals.com arbitration
the Insurance company hires an appraiser. You also hire an appraiser. The two appraisers hire or appoint an umpire.
The appraisers then attempt to negotiate a fair value for your vehicle. If the appraisers are unable to come to an agreement, they then submit their information, documentation to the umpire. The umpire then decides based on the information he/she is given who is more correct.
The umpires decision is final and binding on both parties.
The cost.
You would expected to pay for your appraiser ($250-$500) You would also be expected to pay for 1/2 the umpires fee ($250-$500)
So there you have the basics of arbitration.