There are overheads in the operation of a common queue, which increase the effective time it takes to serve each customer.
- The customer at head of the queue will take time to realise that a server has become free.
- Walking from the queue to the server takes time.
Hesitation and walk time can easily add 5% or more to the time taken to serve each customer. The chart now shows a dashed line for the waiting time for a common queue where the average service time is increased by 5%.
For very busy facilities grouped queues may provide quicker service than a common queue.