Pursuant to CPLR 7511, on a motion to vacate an arbitration award, the burden is upon the movant to show the award was irrational, in violation of public policy or in excess of the arbitrator's powers. Petitioner has failed to meet its burden. In addition, respondent's evidence showing that respondent was diagnosed with lumbar radiculopathy and had been unable to work for a period of five consecutive months is sufficient to support the arbitrator's finding of a serious injury within the meaning of Insurance Law § 5102 (d).