1. Structure of a Waiting Line System Queuing theory is the study of waiting lines Four characteristics of a queuing system: –The manner in which customers arrive (bulk, individual, by appointment or randomly) –The time required for service –The priority for determining order of service –The number and configuration of servers in the system

2. Structure of a Waiting Line System In general, arrival of customers into a system is a random event. Frequently the arrival pattern is modeled as a Poisson process. Service time is also usually a random variable. It is often described by the exponential distribution. The most common queue discipline is FIFO. An elevator however would use LIFO and an emergency room would use a highest cost criterion.

3. Queuing Systems A three part code A/B/s is used to describe various queuing systems where –A describes the arrival distribution assumed –B describes the service distribution assumed –s is the number of channels (servers) per line

4. Operating Characteristics of a Queuing System What is the average wait time of the customer in the queue? In the system? What is the average number of customers in the queue? In the system? What percent of time is the service facility idle? What is the probability that an arriving customer will have to wait?