The main point of the article is that, on freeways, attempts by individual drivers to go faster (changing lanes, etc.) can slow down traffic overall, causing more individuals to change lanes, leading to a downward spiral of traffic delays.
Carlos Daganzo of the University of California, Berkeley, was puzzled by what highway sensors showed: When congested traffic forms upstream of a bottleneck, the rate at which cars at the front leave the congested area decreases. “It's as if, when a line forms at the popcorn stand, the server slows down, so people leave with their popcorn at a slower rate just because there are more people waiting,” he says.
Yet the counterintuitive effect is seen time and again, and in a recent study he and colleagues figured out why. The congestion causes cars to jockey across lanes, ever on the lookout for the faster one. Lane changing increases the gaps between cars, as drivers slow down when someone barges in front of them. Bigger gaps means fewer cars per second leaving the front of the jam.
Does the same thing happen in factories when we expedite? Does that behavior, trying to push a single order/unit through, slow down all the others? From my experience, it does. You'd think it would be easier to control factory flow than thousands of independent freeway drivers! Maybe traffic will be better when we have computer controlled driving that takes that out of our hands?
Mark Graban
Mark Graban is an internationally-recognized consultant, author, and professional speaker who has worked in healthcare, manufacturing, and startups. His latest book is Measures of Success: React Less, Lead Better, Improve More. He is author of the Shingo Award-winning books Lean Hospitals and Healthcare Kaizen, as well as The Executive Guide to Healthcare Kaizen. He also published the anthology Practicing Lean that benefits the Louise H. Batz Patient Safety Foundation, where Mark is a board member. Mark is also a Senior Advisor to the technology company KaiNexus.