PORTLAND — Maine Turnpike Authority officials are disappointed so few motorists used discount fare coupons that were intended to manage traffic flows this summer.

Paul Violette, executive director of the Maine Turnpike Authority, said he anticipated as many as 25 percent of the turnpike users would take advantage of the program. But only about 5 percent used the coupons to get reduced tolls.

The coupons, which were handed out at toll booths and made available in New England publications, entitled drivers who used the 100-mile road during off-peak hours to get free or reduced tolls.

Labor Day, the experiment’s final day, was also its most successful, when 9 percent of the drivers turned in coupons, said turnpike spokesman Dan Paradee.

The experiment was a result of a 1991 state law that barred a planned widening of the turnpike’s southern leg from two lanes each way to three.