WASHINGTON — For the fifth consecutive month the National Restaurant Association’s Restaurant Performance Index remained above 100. At 102.2, the March R.P.I. achieved a post-recession high that was previously reached in December 2011.

“The first quarter finished strong with a solid majority of restaurant operators reporting higher same-store sales and customer traffic levels in March,” said Hudson Riehle, senior vice-president of the Research and Knowledge Group for the N.R.A. “In addition, restaurant operators are solidly optimistic about sales growth and the economy in the months ahead, which propelled the Expectations component of the R.P.I. to its highest level in 15 months.

“Bolstered by improving sales and traffic results, restaurant operators’ outlook for capital spending reached its highest level in more than four years. This will have positive implications throughout the supply chain of the restaurant industry.”

The R.P.I.’s current situation index, which measures current trends in same-store sales, traffic, labor and capital spending, stood at 102 in March, a 0.1% increase compared with February. Restaurant operators reported positive same-store sales for the tenth consecutive month in March, with sales results similar to their February performance. Sixty-five per cent of restaurant operators reported a same-store sales gain between March 2011 and March 2012, up slightly from 63% who reported a sales gain in February.

The R.P.I.’s expectations index, which measures restaurant operators’ six-month outlook, rose to 102.4 in March, a 0.4% increase compared with February. A majority of restaurant operators expect their sales to be higher in the months ahead. Fifty-three per cent said they expect to have higher sales in six months, compared with the same period in the previous year, matching the proportion who reported similarly in February. In comparison, only 9% of restaurant operators expect their sales volume in six months to be lower than it was during the same period in the previous year, also unchanged from last month.

Restaurant operators also are generally optimistic about the direction of the overall economy. Thirty-eight per cent of restaurant operators said they expect economic conditions to improve in six months, up from 35% last month. In comparison, 12% of operators said they expect economic conditions to worsen in the next six months, down slightly from 14% who reported similarly last month.