Batch and Queue, or why does it take so long to get to work?
Delaying anything is adding waste, the waste of waiting, it is better that things flow steadily rather than keep stopping while people wait for something to happen then off again at high speed. Lean manufacturing and Just in Time (JIT) is about creating flow and removing delays, how does this compare to everyday life?
Consider my journey to work this morning, my company moved offices to the other side of the city that I work in so my journey has increased significantly from the original 5 minutes that it used to take to around 40 minutes. But the increase in distance is not that huge, only around 12KM, so why does it take so long?
On my drive this morning I timed how long I was physically travelling for and for how long I sat at traffic lights and was delayed in bottlenecks where several roads converged into one route. The results do not make good reading, I was travelling for only 9 minutes of my 38 minute journey, the other 29 minutes my car was stationary belching out fumes while I waited for lights to change, or I was trying to fight my way through a crush of cars desperately trying to go from several lanes into just 2 or 3.
This is quite similar to many factories that I have worked in over the years, the operators will sit or stand there for several minutes while a machine is cycling doing nothing else, or they will wait for the previous operation to pass them a batch of product to work on, much like sitting at the traffic lights waiting. Then you have the bottle neck situation with many production operations all filtering into one process that is not capable of keeping up with the demand required of it, normally one huge expensive “super” machine that serves the whole factory.
Consider the Dutch town Drachten, they have conducted an experiment here now for several years and switched off all of the traffic lights, the drivers all report that there are no longer any tail backs or delays and that the traffic flows freely and safely! Flow without delays, isn’t this what we want in our factories?
Consider also the City of Milton Keynes in the UK, famous for it’s concrete cows and the roundabouts, I used to live there until just a couple of years ago, traveling around the cities grid system was great, you could get anywhere in the city easily and quickly on it’s network of roads, if one was slow or blocked, you just went across one block and off you went again, few if any delays, a real delight to drive. But it still had its bottle necks, where several roads approached the motorway you had delays and queuing traffic at peak times, so what did they do? They introduced a series of delays on the approaching roads to reduce the amount of traffic reaching the bottle neck, so that no traffic built at the bottle neck itself. These traffic lights on the approaching roundabouts may have reduced the problems at the bottle neck but all they did was move the problem to the approaches of all of these roundabouts, where the problem became even worse as it delayed traffic on other routes as well as that to the motorway and was there all day and night long rather than just at peak periods!
They “solved” the problem at the bottle neck, but all they did was delay the speed at which traffic approached and moved the problem elsewhere, the problem was the capacity of the bottleneck, not the volume of traffic, it was this bottleneck that needed to be dealt with not the volume approaching it!
The traffic is batched at each set of lights, the flow from the process (the road leading to the light) is collected together in one batch before being released into the next process (the next road) only to again be batched together at the next set of lights. I traveled from next to where I work a few nights ago at 4am (don’t ask why) and ignored the traffic lights on my journey home, it took 7 minutes (without breaking the speed limits), not 40 minutes!
Another example of the superiority of flow is the roundabouts here, despite the fact that the drivers here ignore most of the road rules the flow around the roundabouts is fairly constant but there are still queues at peak times. However you can always tell when the traffic police have decided to “improve” the situation by stopping the incoming traffic from each road in turn to speed up the flow of traffic around the roundabout, when they do this the queue on the approach to the roundabout is normally 3 to 4 times longer than normal, but they still do it! Flow is superior and faster than batch and queue every time.
We see delays everywhere we look in our everyday life and we complain bitterly, when was the last time you sat happily waiting to see a doctor or a dentist in the “waiting” room! You arrive for your “appointment” and you then wait!
Why do we complain about it in our everyday life but we accept it in our workplaces? We need to work on implementing the principles of lean manufacturing to remove these delays so that we can achieve flow through Just In Time principles.