QUEUING THEORY

When limited facilities fail/delays to satisfy demands made upon them, problems occur which generate queues or waiting lines. Illustrations are:

•    Customers waiting at cash desks in a supermarket or bank
•    A stock of items in a warehouse awaiting storage
•    Letters in an ‘in’ tray waiting to be opened
•    Telephone calls to a switchboard waiting to be answered.

In business, queues have certain ‘economic’ or ‘cost’ implications;

It may be too costly for a company to allow long queues to develop. E.g. if employees queue up at a store counter for new material supplies, the company will incur the cost of idle time and lost production due to their time spent waiting.

It will probably be costly to speed up service, and thus reduce waiting time and queue lengths because it would be necessary to employ extra service assistants, service counters or service equipment.

Customers may expect to be served within a certain length of time; otherwise they may take their custom elsewhere. Queuing problems are therefore concerned with:

•    Average waiting times
•    The average length of queues (i.e. the average number of people in a queue or service system)
•    The cost of a servicing system.

The management may therefore wish to provide a servicing system which either: minimize the joint costs of: a) servicing customers b) (idle) time waste by customers in the queue or balance the requirement to provide a satisfactory service time with the interests of economy i.e. to provide a reasonably quick service but at a relatively low cost.