SOUTHFIELD, Mich. — U.S. automobile sales in September may have run at the fastest pace since March as consumers returned to showrooms, helping the industry recover from the worst year in almost three decades.

Industrywide deliveries, to be released today, might have reached an annual rate of 11.7 million vehicles in September, the average of nine analysts’ estimates compiled by Bloomberg. That would top the 9.4 million pace of last September, the month after the U.S. “cash for clunkers” program ended, and match March’s 11.7 million rate, according to Autodata Corp.

Consumers are slowly returning to dealers’ showrooms while remaining concerned about the security of their jobs, said Paul Ballew, chief economist for Nationwide Mutual Insurance Co. in Columbus, Ohio. Deliveries for all of last year fell to 10.4 million, the lowest since 1982, compared with the average 16.8 million vehicles a year from 2000 to 2007.

“It confirms to us that the recovery has gained a little bit of momentum in the third quarter and is somewhat back on track, but it is still a very slow recovery,” Ballew, a former General Motors economist, said in a telephone interview.

The Conference Board reported Tuesday that consumer sentiment this month declined to the weakest level since February. The unemployment rate was 9.6 percent in August, up from 9.5 percent in July.

The U.S. auto selling rate has stayed above 11 million since March, according to Autodata, a research firm based in Woodcliff Lake, N.J.