Chapter 13. Queuing Analysis

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Waiting in queueswaiting linesis one of the most common occurrences in everyone's life. Anyone who has gone shopping or to a movie has experienced the inconvenience of waiting in line to make purchases or buy a ticket. Not only do people spend a significant portion of their time waiting in lines, but products queue up in production plants, machinery waits in line to be serviced, planes wait to take off and land, and so on. Because time is a valuable resource, the reduction of waiting time is an important topic of analysis.

The improvement of service with respect to waiting time has also become more important in recent years because of the increased emphasis on quality, especially in service- related operations. When customers go into a bank to take out a loan, cash a check, or make a deposit; take their car into a dealer for service or repair; or shop at the grocery store, they increasingly equate quality service with rapid service. Aware of this, more and more companies are focusing on reducing waiting time as an important component of quality improvement. In general, companies are able to reduce waiting time and provide faster service by increasing their service capacity, which usually means adding more servers, such as more tellers at a bank, more mechanics at a car dealership , or more checkout clerks at a grocery store. However, increasing service capacity in this manner has a monetary cost, and therein lies the basis of waiting line analysis: the trade-off between the cost of improved service and the cost of making customers wait.

Providing quick service is an important aspect of quality customer service .

Like decision analysis, queuing analysis is a probabilistic form of analysis, not a deterministic technique. Thus, the results of queuing analysis, referred to as operating characteristics, are probabilistic. These operating statistics (such as the average time a person must wait in line to be served ) are used by the manager of the operation containing the queue to make decisions.

A number of different queuing models exist to deal with different queuing systems. We will eventually discuss many of these queuing variations, but we will concentrate on two of the most common types of systemsthe single-server system and the multiple-server system.