What is Queueing Theory?

M.R. Anglin

Queueing theory is used to study the phenomenon of waiting in lines. Some people use the information gathered from queuing theory in order to determine how to best serve customers and so prevent them from waiting in line longer than they have to. The theory allows researchers to analyze several things such as arriving in line, waiting in line, and the time it takes to service customers. This allows them to gather and derive information on a customer’s waiting time, the expected amount of customers that will be in a line, the probability of a customer encountering a line, as well as other data. This information is used in order to find ways to reduce lines and wait time.

Customer wait in line to pay at a restaurant, at the grocery store and in a number of other places.
Customer wait in line to pay at a restaurant, at the grocery store and in a number of other places.

Applications of queueing theory are used in many aspects of business, customer service, commerce, industry, healthcare, and engineering. Customer service applications can especially make use of the information gathered by queueing theory. This information can be used in order to make decisions on the kind of resources needed to provide service for customers. The data can be also be applied to call centers, network server queuing, telecommunications, and traffic flow. It can even be used to dictate what type of line customers will be standing in while waiting for different types of service.

There are several queueing disciplines that have been developed because of queueing theory—four of which are First In First Out (FIFO), Last In First Out (LIFO), Processor Sharing, and Priority. FIFO describes the practice of serving customers in the order they arrive in so that the person waiting longest is served first, while LIFO describes the practice of serving customers so that the person who comes in last leaves first, such as in the case of riding an elevator. Processor sharing serves customers at the same time to that the average waiting time for all customers is about the same. The Priority discipline serves the customer with the highest priority first. It is important to note that these disciplines can be applied to applications other than customer service.

Examples of how queueing theory works is present in many aspects of everyday life. At bank tellers and credit unions, one may see one line and multiple tellers. This happens to help ensure that one slow transaction does not hold up the entire line. Some stores open more registers if there are more than three people waiting in a line. There are also other stores that have roaming clerks. These clerks ring up purchases and give customers a number so that the cashier can complete the transaction quickly, thus reducing waiting times for all.

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