# Queueing theory

**Queueing theory** is the mathematical study of waiting lines, or queues.[1] A queueing model is constructed so that queue lengths and waiting time can be predicted.[1] Queueing theory is generally considered a branch of operations research because the results are often used when making business decisions about the resources needed to provide a service.

Queueing theory has its origins in research by Agner Krarup Erlang when he created models to describe the system of Copenhagen Telephone Exchange company, a Danish company.[1] The ideas have since seen applications including telecommunication, traffic engineering, computing[2] and, particularly in industrial engineering, in the design of factories, shops, offices and hospitals, as well as in project management.[3][4]