The ratings firm Standard & Poor’s yesterday raised Avis Budget Group Inc.’s corporate credit rating from ‘B+’ from ‘B-’, citing the car rental company’s improved operating performance.

S&P said it also raised other ratings on Avis Budget by two notches, and the recovery ratings on the company’s secured and unsecured debt remain unchanged. The outlook is stable.

“Following a very challenging 2008 and early 2009, Avis Budget Group Inc.’s operating performance has improved and we expect further gains over the coming year,” S&P said.

S&P said Avis Budget is benefiting from improved industry fundamentals, cost-cutting measures, and efficiency-improvement initiatives it implemented over the past year.