OK! So how many readers spotted the relationship with yesterday's driving variation out of the constraint techniques and Goldratt's 2nd step in the 5 focusing steps of TOC - exploit the constraint? Yes, driving variation out of the throughput variable in the constraint is an exploitation technique. By reducing variation, we can guarantee that we get the maximum performance from the bottleneck resource.

Notice how I carefully selected the variable I was going to focus on. I could have chosen the speed of the vehicles or the vehicles-in-process inventory (the density of traffic) on the freeway, but instead I chose to focus on the distance between traffic and the rate of cars passing the bottleneck point at the entrance to the bridge - the takt time at the output of the bottleneck. By careful selection of the variable for variation reduction I can align the techniques of Deming and Six Sigma with the five focusing steps from Goldratt's Theory of Constraints. The flip side of this is that unfocused reduction of variation produces little productivity improvement. This is the main criticism of 6 Sigma leveled at it by the TOC community. This example shows that it doesn't have to be an either/or choice - you can do both!