Commuters who are sick and tired of rude riders have an ally: The MTA. The agency is unveiling a new campaign that aims to inject courtesy into daily commutes.

Starting in January, the MTA will install placards touting its "Courtesy Counts, Manners Make a Better Ride" campaign on thousands of subway cars. Signs also will be installed on buses and commuter railroads.

Some of the do's include letting passengers off first and offering seats to the elderly, disabled and pregnant.

Some don'ts include primping, eating and taking up extra seat space on trains.