The Massachusetts Bay Transportation Authority recently rejected advertising for co-working space The Wing because it said that the company's advertising was too political.  

The Wing is a co-working and community space that targets, and is designed to meet the needs of, women.  According to media reports, The Wing tried to place advertising in MBTA subway stations that said things like, "MUTE THE MANSPLAINERS" and "THE WORLD WAS BUILT FOR MEN.  THE WING WAS BUILT FOR YOU."  Apparently, the MBTA said that the concepts violated the MBTA's prohibition on "political issues or matters of public debate."  The MBTA does not allow advertising that, "concerns political issues or expresses or advocates an opinion, position, or viewpoint on a matter of public debate about economic, political, moral, religious, or social issues." 

Like other transit systems, the MBTA has detailed guidelines about the types of advertising that it will accept.  In addition to prohibiting advertising relating to political issues, the guidelines also prohibits the following categories of advertising:

• Demeaning or disparaging advertising; 
• Advertising that promotes tobacco products;
• Advertising that contains profanity;
• Advertising for firearms or that contains the prominent use of firearms;
• Advertising that contains graphic violence;
• Advertising that promotes or encourages the use of unlawful goods or services; 
• Advertising that promotes or encourages unlawful conduct; 
• Advertising that contains obscenity or nudity; 
• Advertising that contains material that describes, depicts, or represents prurient sexual suggestiveness; 
• Political campaign advertising;
• Advertising that falsely suggest the endorsement of the MBTA; 
• False or misleading advertising; 
• Libelous or infringing advertising; and
• Advertising for adult-oriented goods or services.

The MBTA also allows advertising for alcohol products in limited circumstances.

It's important to remember that when you're planning to advertise in public transit systems, they've got their own, often idiosycratic, guidelines about what they will and will not accept.  So if you're planning to do anything political, or edgy, or that might be controversial, you should run the concepts by the transit system early, to make sure that they'll be accepted.