Fare evasion or fare dodging is the act of travel without payment on public transit. When considered problematic, it is mitigated by revenue protection officers and ticket barriers, staffed or automatic, are in place to ensure only those with valid tickets may access the transport. The term fare avoidance is sometimes used as a euphemistic synonym and sometimes used to refer to the lawful use of much cheaper tickets.

Fare evasion and fare fraud may or may not be a crime, depending on jurisdiction.

One method of fare evasion is jumping or climbing over the turnstiles which bar the entryway into a subway system; hence the term, "turnstile jumping". Fare-dodgers also can walk right behind a passenger with a valid ticket before closing of some types of ticket barrier gates (this is called tailgating). Other methods include adults traveling on children's tickets, or using discounted tickets or free passes that the passenger is not entitled to. They also can purchase valid tickets for shorter journeys in order to get through the entry and exit barriers at a lower price than their actual journey, or board a vehicle with just a platform ticket (called "doughnutting", as the ticket coverage looks like a doughnut on the Tube map). Fare evasion on trains or subways is also called "bumping trains".

On vehicles fare-dodgers usually try to avoid ticket inspectors or conductors. On commuter trains with a sufficient number of passenger coaches one of the most common methods is walking away from ticket inspectors to other coaches and running on the platform in the opposite direction to the coaches that ticket inspectors already passed. On short commuter trains or especially intercity and long-distance passenger trains fare-dodgers can hide from ticket inspectors in toilets, luggage compartments, staff rooms and other utility chambers and cells inside the train.^{[citation needed]}

Another issue occurs on the bus or tram; passengers either bypass the bus driver or enter through the rear door of the vehicle. If a bus or tram has a turnstile installed in it, fare-dodgers can jump over or crawl under the turnstile. In most countries passengers board a bus from any door, validate their tickets at machines and have no contact with the driver, thus increasing the potential for fare evasion.^{[citation needed]}

A dangerous method of fare evasion practiced in some countries is riding on exterior parts of a vehicle (rooftops, rear parts, between cars, skitching, or underneath a vehicle), also known as "vehicle surfing" (train surfing, car surfing). Fare dodgers may engage in this practice if it is very hard or impossible to hide from ticket inspectors inside a vehicle.

Turnstiles are used to obstruct invalid access. Turnstiles may be replaced with ticket barriers in a less easily transversed form, or may be integrated more closely with an electronic ticket system. Ticket barriers can also require the travellers to show their tickets upon exiting. Typically turnstiles are used at train stations, however some city transit systems install turnstiles inside city street vehicles, for example buses and trams.^{[citation needed]}

As of 2006,^[update] panic bars on emergency exit doors were approved for installation in all stations of the New York City Subway. Panic bar alarms have been silenced since 2014 due to regularity of non-emergency passenger use.