Public transportation is open to all — except when it’s not. Amtrak may kick you off if you stink, and the Montgomery County bus may eject you for engaging in unwanted conversation. Whether traveling by train, taxi, bus, subway, or aircraft, public transportation providers set a host of restrictions about who can travel and on what terms.

My interest in the topic was piqued after recently reading Amtrak’s contract of carriage, printed on the reverse of my ticket. They reserve the right to refuse service to people who meet a variety of conditions. In addition to the expected rules regarding following the rules and following security procedures, they also reserve the right to eject anyone with “objectionable” conduct, “offensive” personal hygiene, and who pose a health, safety or security hazard.

Air travel is generally governed by the Warsaw Convention and airlines maintain their own specific policies. US Airways’ contract of carriage gives the airline the right to remove from any flight people who meet one of ten reasons, including refusal to follow government regulation, babies less than 1 day old, people who appear to be intoxicated or under the influence of drugs, people with a contagious disease their medical adviser determines to be a “direct threat” to the health and safety of others, or are abusive or violent. Greyhound doesn’t have a legal contract on their website, but their information webpage informs passengers they have “zero tolerance for alcohol, drugs, weapons and unruly behavior,” and a ban on animals.

The New York City subway’s detailed rules of conduct says nothing about illness or hygiene, but does prohibit a wide variety of behavior, including barring those who “conduct himself or herself in any manner which may cause or tend to cause annoyance, alarm or inconvenience to a reasonable person or create a breach of the peace.” I’ve been on plenty of buses with people who “tend to cause annoyance.”

Here in D.C., Metro’s rules take the form of “Dos” and “Don’ts” for the rail and bus systems. Although the Metro Police are empowered to enforce WMATA policy, I can’t seem to find a more formal statement of policy for riders, although they do have a detailed policy regarding the use of WMATA property.

In the suburbs, Montgomery County’s Ride On bus has a policy banning disruptive behavior, including “unwanted touching or conversation with another passenger,” as well as yelling, spitting, fighting, and eating. The rules for taxicabs focus mostly on unfair discrimination, but municipal regulations allow cabs to refuse transportation when they “has reason to believe the person is engaged in a violation of law,” or “The operator has cause to fear injury to his or her person, property or taxicab.”

The policies raise interesting questions: do those carrying highly contagious diseases have a right to use public transit, even if it means risking spreading infection? (What if they have no other way to the clinic?) Should commuters be forced to tolerate riding with people with bad personal hygiene, or with people who may engage in unwanted conversation? Where’s the line between behavior that is encouraged and that which is required?