What You Can Learn in Traffic about Lean Manufacturing

As a resident of the Puget Sound area of Washington State, the subject of traffic flow is one of high interest to me. Traffic around the Seattle consistently ranks in the worst five in the United States. So a July 1, 2005 Wall Street Journal article titled “How Brief Drop in Cars Can Trigger Tie-Ups, And Other Traffic Tales” caught my attention.
The article describes some counterintuitive findings of traffic engineers. They make quite a bit of sense from a Lean thinking standpoint. In short, traffic jams can happen because individual cars try to speed up. This causes other cars to brake, resulting in more of the same behavior.
“Weaving” or looking for the open lane in a highway causes the reduction in road space since you can not occupy the empty spaces that cars are using to change lanes. This reduces overall capacity, slowing down traffic flow. When other cars are changing lanes in congested traffic you brake, resulting in more lane-seeking weaving behavior. The advice is to stay in your lane in congested traffic, and you will get there sooner. Slow and steady wins the race for everyone.
Weaving and lane changing causes more braking, creating a chain reaction and slowing down traffic overall. This has very interesting parallels to what we find in manufacturing, as well as supply chains. In complex manufacturing workflows, when the locally optimized processes with faster cycle times are allowed to “weave and change lanes” by producing ahead in batches, this creates the same type of overall slowdown in production throughput times.
The idea of Lean manufacturing is to keep the work moving smoothly and steadily rather than in short, quick responses. The goal is to have the lowest cost and the fastest speed overall, rather than highest utilizations or locally optimized processes.
In the words of Prof. Treiber quoted in the Wall Street Journal article, “If you brake just in time, you can usually safely break less,” he says, “which improves the flow.” Spoken like a true Lean thinker.
Traffic and workflow in a factory is certainly not a perfect analogy, but the next time you are in heavy traffic think about your lane-seeking behavior and the psychology of those around you. Compare it with how traditional resource allocation is done in manufacturing (as well as transactional work). Take the opportunity to practice Lean thinking on the highway to promote smooth one-piece flow of traffic.