Different public transit systems across the United States have different rules and procedures for paying the fare. Children under a certain age or below a certain height sometimes can ride for free or for a lower fare; the elderly and disabled usually ride for a discounted price.
Most mass transit buses accept cash fares; almost all buses accept coins. However, a passenger has to have exact change because bus drivers do not make change. Some buses accept tokens that you can buy at some bus depots or train stations. Across the country, more and more buses use a fare card system. These are cards loaded by passengers with a certain amount of money; it could be a day, week, month or annual pass. They are swiped, tapped, or scanned when riding. The fare is automatically deducted. What is good about a fare card is that they can be reloaded via the Internet or by phone, so a passenger doesn't need to go to a station to add money. Fare cards also make transferring from one bus line to another easier. Many cities even allow for free transfers from one bus line to another when using a fare card.
Light rails, subways, and trains usually have a similar system of paying your fare. However, people cannot pay to ride using cash since there is no one there to collect the fare. Most rail-based mass transit systems require a token or a fare card. Many rail systems have turnstiles that are locked until you swipe or tap your fare card. Some people do not like fare cards because they worry about where they are going being tracked.