Waiting Line Models
Waiting line or queuing systems are pervasive. Many of us remember the long lineups in front of stores in the Soviet Union and Vietnam, and we have all experienced lineups in banks and supermarkets, but there are many more instances with waiting lines: think, for instance, about traffic lights, where drivers line up and wait, files that wait for processing in the inbox at a clerk’s workstation, or telephone calls that are put in a queue. Queuing system were first examined by Agner Krarup Erlang (1878–1929). Erlang was a Danish mathematician, who worked for the Copenhagen Telephone Company. One of the questions he faced during this time was to determine the number of telephone circuits that are required to provide an acceptable level of service.