Roads, Demand and the Law of Unintended Consequences
Thoughts from a (very busy) Manchester or Moscow Ring Road
On google maps the distance from my home to Oldham is just over 50miles and should take just under an hour. Why then have I been stuck on the M60 for over 50minutes and why is my navigation system saying it will take a further 55minutes to get home?
Why is it that when countries build bigger roads it actually makes traffic worse? It is a complex system issue that has many parallels with what we find in many lean manufacturing and service scenarios. Five or so years ago I was sat, stuck in traffic, in a taxi with John Darlington on the third (yes, third after the Boulevard and Garden) Moscow ring road. The taxi driver commented that they were thinking of building another to cope with the demand……. He laughed and said that there would soon be as many as the rings on a great tree trunk. So, why does this happen?
It is all about demand, capacity and flow. With uncanny foresight John Bicheno was only today talking the students through road and traffic examples to illustrate the power of the interrelated parts of Kingman’s formula. There are significant insights to be gained from it which is why he calls it “the equation of lean”. It is one of the big five concepts that are at the heart of this module. I think that my particular queue was due to process variation. At a time when the road was at peak load a vehicle breakdown had reduced the capacity of the system by 33% (a lane). As utilisation went beyond 80% the queue began to build exponentially. Knowing the theory about what happened isn’t such a comfort when you are stuck!
Road to Nowhere – Induced Demand – The Unintended Consequence
Demand and customer value should always be the first thing to study. Road building is a good example of how incentives, policies and human behaviour have confounded rational logic. Why don’t we just widen our busy roads every child asks from the back of the car? We don’t because it has been found, at great cost, that this can itself induce more demand. New roads motivate us to go on more and longer journeys. Also new ring roads syphon traffic from the side roads to the big new roads. Take the M25 as an example. In the year 2000 a Government study concluded that no amount of widening would deal with congestion. It was widened nonetheless. Nowadays the Government prefers using the hard shoulder, varying speed limits and controlling the entry ramps at junctions. The irony is that most roads have high levels of unused capacity. Perhaps staggering the work day would have a bigger impact?