Every time demand exceeds capacity a queue is formed, which means that customers have to wait for service.
Queuing models are designed to help determine an appropriate level of service. These models consider:
1. The speed of the service, and
2. The optimal number of service stations
The goal is to minimize the cost of providing the service.
Turban, E. and J.R. Meredith (1985): Fundamentals of Management Science. Third Edition Business Publications, Inc.