T pushes for courtesy - with a light touch

“Please, simply do the right thing,’’ all 1,500 posters ask.

“What we’re trying to achieve is a better experience for all of our customers,’’ said Jonathan R. Davis, acting general manager of the Massachusetts Bay Transportation Authority, and a daily bus and subway commuter from Medford who has observed his share of etiquette indiscretions.

After taking the helm last month, Davis asked the marketing department to come up with a new courtesy campaign and to try adding a dash of humor. The design work was done in-house, and the printing costs were $2,500 for the ads, which will remain up until early next year.

The previous round of courtesy ads, released in May 2010, carried straightforward slogans (“Stand up for others,’’ “Put others first’’) and portraits of riders, augmented by a recorded announcement from Celtics star Paul Pierce.

“It’s good to periodically remind our customers,’’ Davis said. “This not only reinforces the prior message, but freshens the approach.’’

This campaign marks at least the fourth courtesy effort by the T since October 2006, when the transit agency responded to a Globe column about callous commuters by posting 1,000 politeness placards and distributing hundreds of $2 Dunkin’ Donuts gift cards to riders who displayed good behavior. In the past, T officials have noted an anecdotal improvement in courtesy, but have said the effect wanes over time, requiring new reminders.

Making his way to the Red Line yesterday, Eugene McCarthy welcomed the new signs, saying he hoped they would translate into more riders surrendering seats to those who really need them and fewer trimming their nails on the train, stray clippings flying.

“I just cringe,’’ said McCarthy, 36, of Quincy.

It is enough to make the courteous pine for the good old days of decency, an era, transit historian Bradley H. Clarke said, that is as much myth as reality.