Increases in customer traffic and same-store sales lifted the National Restaurant Association’s performance index to a 14-month high in May.

Restaurant owners optimisticThe Washington, D.C.-based NRA said the Restaurant Performance Index rose to 101.8 in May, up 0.9% from April. The May score was the third month in a row the index has gained ground. That upward trend indicates greater optimism about future business prospects, according to a news release from the group.

“The May increase in the Restaurant Performance Index was driven by broad-based gains in the current situation indicators, most notably positive same-store sales and customer traffic results,” Hudson Riehle, senior vice president of the Research and Knowledge Group for the National Restaurant Association, said in the release. “In addition, restaurant operators remain optimistic about continued sales growth and a majority plan to make a capital expenditure in the next six months.”

Most restaurant operators realized higher sales in May, with 63% reporting same-store sales gains between May 2012 and May 2013. Just less than half of operators reported stronger same-store sales in April.

About one out of five operators reported lower same-store sales in May, compared with one out of three who reported same-store sales declines in April.

Traffic levels rose for 47% of operators in May, up from 36% in April. Thirty percent of operators reported traffic declines in May, down from 40% in April, according to the release.

The NRA’s Expectation Index, measuring the six-month outlook for the industry, rose to 102.0 in May, the highest level in 12 months, according to the release.

The Restaurant Performance Index is compiled from responses to the National Restaurant Association’s Restaurant Industry Tracking Survey, a monthly polling of operators on industry indicators such as traffic, labor and capital expenditures, according to the release.