A "Flow Line" comprises work stations with random processing times. This is usually the case if human workers are used. Besides the average processing time for each station also the coefficient of variation (=standard deviation/average) to account for the amount of randomness of the processing time must be specified. In a certain sense, this type of flow production system is equivalent to a system with deterministic processing times, but with a mix of different products produced on the same line. At each station, each product may have a specific processing time.
The work stations are decoupled with the help of buffers of limited size.