WASHINGTON — The National Restaurant Association’s Restaurant Performance Index (R.P.I.) climbed 1.4% in March to 100.5, its strongest level since September 2007. In addition, the restaurant operators who participated in the survey expressed increased optimism about growth in sales and staffing.

“The R.P.I.’s solid performance in March was driven by improvements among both the current-situation and forward-looking indicators,” said Hudson Riehle, senior vice-president of the Research and Knowledge Group for the N.R.A. “Restaurant operators reported net gains in both same-store sales and customer traffic in March, the first time in 31 months that both indicators stood in positive territory.”

The R.P.I.’s current situation index, which measures four industry indicators including same-store sales, traffic, labor and capital expenditures, stood at 99 in March, up 2.4% from February’s level of 96.7. Although the same-store sales and traffic indicators turned positive in March, the labor and capital expenditure indicators continued to lag.

The expectations index, which measures restaurant operators’ six-month outlook for same-store sales, employees, capital expenditures and business conditions, stood at 101.9 in March, up 0.5% from February and its strongest level in nearly three years. In addition, the expectations index stood above the 100 level for the third consecutive month, which signifies expansion in the forward-looking indicators.

The rising expectation index indicates restaurant operators are growing more optimistic about their sales prospects in the months ahead. Fifty per cent of restaurant operators expect to have higher sales in six months, compared with the same period in the previous year, up from 44% who reported similarly last month and the strongest level in 33 months. In comparison, just 15% of restaurant operators expect their sales volume in six months to be lower than it was during the same period in the previous year, compared with 16% who reported similarly last month.