Queue areas are places in which people queue (first-come, first-served) for goods or services. Such a group of people is known as a queue (British usage) or line (American usage), and the people are said to be waiting or standing in a queue or in line, respectively. (In the New York City area, the phrase on line is often used in place of in line.) Examples include checking out groceries or other goods that have been collected in a self service shop, in a shop without self-service, at an ATM, at a ticket desk, a city bus, or in a taxi stand. Queueing is a phenomenon in a number of fields, and has been extensively analysed in the study of queueing theory. In economics, queueing is seen as one way to ration scarce goods and services.