In the much praised book Flow about product development the management of queues and bottle necks are a central theme. The book states principles on how to best deal with them. Traffic lanes and cars are great for showing the (wrong) use of queuing because most people can relate to traffic jams and bottlenecks in a traffic situation.
One major topic of any process optimization is the management of bottlenecks. One intriguing statement is made, it urges to go beyond the popular idea that ‘the capacity of the bottleneck controls system flow’. It’s not only the bottleneck, it also very important to look at the flow through the bottleneck.
The example given in the book discribes a traffic situation where three lanes are reduced to two. Combining two lanes into one causes turbulence and you don’t want this turbulence at the bottleneck, which is why the narrowing process starts miles before the actual bottleneck.
Although this is better to leave the narrowing totally unmanaged, in practice it often doesn’t work like this. On a recent car trip I found there is a better way of controlling flow which works much better than the regular solution, I’ll explain.
First the basic problem found very often on the Dutch highway, three lanes need to be narrowed to two:
The regular solution is to urge the car driver to start ‘turbulenting’ a few hundred meters before the third road ends. This usually doesn’t happen, what does happen is people cram their car into the bottleneck, usually with high speed. Their motivation is to slip through (escape) the bottleneck as quickly as possible. This decreases flow sometimes to a standstill.
An alternative solution, I recently experienced, is much more focussed on flow. This solution takes a two step approach, it splits the three lanes into two before combining them. This way the driver in the middle lane has two options when merging with another lane, to the left or right lane. This spreads the turbulence more evenly over the two other lanes. It also makes it undesirable to drive up to the road block as fast as possible because you haven’t ‘escaped through the bottleneck’ yet because the real bottleneck is still a few hundred meters ahead.
I’m not sure if the road workers made this arrangement on purpose to increase flow, but it’s a brilliant way of dealing with a bottleneck and minimizing it’s impact.
The relevance to organizations is to keep in mind that widening a bottleneck might not have the highest value, optimizing flow through the bottleneck can also reap huge benefits.
Suppose you have too few testers in your team. One thing you can do is hire more testers. But instead you can make sure the flow of work through the testers is optimal. In stead of the tester testing a feature as a whole after (or even before) it’s developed, involve the tester a few short times during development. This way he/she can detect testing issues before the full test and spread the ‘testing turbulence’ over a longer period of time, reducing the impact of tester-shortage. No extra testers, but increased flow. This is how I prefer to tackle bottleneck issues in my team, when increase in capacity is not at hand.