Introduction
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The study of waiting lines, called queuing theory, is one of the oldest and most widely used
quantitative analysis techniques. Waiting lines are an everyday occurrence, affecting people
shopping for groceries, buying gasoline, making a bank deposit, or waiting on the telephone for
the first available airline reservationist to answer. Queues,* another term for waiting lines, may
also take the form of machines waiting to be repaired, trucks in line to be unloaded, or airplanes
lined up on a runway waiting for permission to take off. The three basic components of a queuing
process are arrivals, service facilities, and the actual waiting line.
In this chapter we discuss how analytical models of waiting lines can help managers evaluate
the cost and effectiveness of service systems. We begin with a look at waiting line costs and
then describe the characteristics of waiting lines and the underlying mathematical assumptions
used to develop queuing models. We also provide the equations needed to compute the operating
characteristics of a service system and show examples of how they are used. Later in the
chapter, you will see how to save computational time by applying queuing tables and by running
waiting line computer programs.