How is it possible that queues occur even when the utilization is lower than 100%?
a Long setup times can increase the utilization to above 100% at which point the system is no longer workable.
b Larger batch sizes cause some units to be waiting while others are worked on.
c Because employees are lazy and wait for a queue to occur before they start working.
d Variability causes the system to sometimes sit idle (but this time cannot be stored) and be really busy at other times (leading to queues).