This version of the game introduces many possible variations for the player to investigate. We will start by observing how buffer management through use of the drum, buffer, rope (DBR) control method affects the flow.
The weakest link for the game below is station 6 and so we will let it control the flow of people into the system.
As you play the game you will notice that the deliberate use of a queue or buffer of people in front of the slowest step means that it nearly always has a sufficient number of people waiting to be treated, so the probability of rolling a die value that is higher than the people in the buffer is low.
You will also notice that if the slowest step rolls a succession of low values, the buffer level may increase to a relatively high value. However, when this station treats a low number of people in a round, the number of new people introduced into the system is also low. As this feeds through, it ensures that the buffer does not become overly large.
A third observation is that, because the flow into the system before the buffer and the flow after the buffer is all controlled by the slowest step, all other the other stations usually have sufficient capacity to service their own queues. In other words, queues are unlikely to grow to unmanageable or significant sizes in other parts of the system.
Moving the position of the slowest step can affect what buffer level is required to minimise the probability that the queue length is shorter than the capacity of that step in a round. For example, consider the case where the second station is slowest step.
As this step controls the input into the system, then whatever passes from station 2 to station 3 will be exactly replenished by an equal number of new arrivals from station 1 to station 2. Given that station 2 can only treat a maximum of 6 people in any round, then imposing a buffer level of 6 is sufficient to ensure that all the available capacity of station 2 will always be used. This is in contrast to the game state below where the slowest step is once again station 6.
In this situation a buffer level of 6 was specified, however, as there is still some random variation in throughput upstream, this initial level is seen to be too low to always ensure that the slowest step always has enough people to work with, so in round 6 the slowest step has rolled a 3 and only has 2 people in the queue. Increasing the initial buffer size can mitigate this.
In general, as the potential for variability, and the delay for controlled feed into the system reaching the buffer increases, as occurs when the slowest step is nearer the end of the chain of services, it may be necessary to impose a higher desired buffer value for such cases. However, the details do depend on the specific variability and the average capacity of steps preceding the slowest step.
These effects also come into play when a manual intervention is made to increase or reduce the buffer. This might be done when you perceive there to be a possibility of the buffer running low or being too high. The intervention controls new entry into the system. However, there is a delay to its effect on the number in the buffer as the effect of the intervention has to travel through all the preceding steps first. So, in the example game shown above, you might want to boost the buffer by introducing more people into the system. However, any increase in new introductions will take at least 5 rounds to reach the buffer. Similarly, in the game below, you might want to reduce the number in the buffer by reducing the number of new people introduced into the system. Again, any reductions will take at least five rounds to reach and affect the buffer.
So the time lag between action and effect depends on how far away the buffer is from the start of the chain of services. Again, you can control whether warnings are issued at high or low buffer values by setting the desired buffer level.