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The Traffic Analogy

27 October 2023
Multiple lanes of stationary traffic

For the last few weeks Wales, and indeed it would seem the entire UK (?!), was gripped in the middle of the dystopian NIGHTMARE that is 20 MPHgate.  As part of Wales’ commitment to Future Generations, and like, listening to actual evidence, Welsh Government sought to proactively lower residential speeds to 20mph to increase road safety, reduce carbon emissions and expand opportunities for active travel. Exemptions could be sought, average car speeds in cities are 21.5 mph anyway, so what was the big deal?

My view on this is simple.  God forbid, but if my child was ever unfortunate enough to be hit by a car when crossing the road, I would hope the car was travelling at 20 mph rather than at 30. That thought alone holds me true.  And yet, many other people seem not to have the same grounding reference point. I’m the first to start moaning at a terrible service experience, believe me (or read 76% of my blog posts) but it seems that there is no end of people who are ready to spew forth intense amounts of bile at the indignity of being forced to travel at slighter slower speeds.

I have found the extreme public reaction to this policy change completely baffling. And yet, I have thought about speeds when driving my car A LOT.  You see cars and lanes and driving speeds are my ‘go to’ lean analogy. Like healthcare, travelling in a car in some form or other, is something that we all experience – ergo traffic and being ill both provide amazing opportunities to illustrate different operations management concepts to others, helping to turn abstract statements into relatable examples.

“Lead time reduction” is the fundamental purpose of a lean approach and achieving flow (a.k.a. speed) is a key element of achieving this.  As I’m driving my car around I am in the middle of my own real time flow experiment. The variety of lanes, roadworks, different car speeds, traffic light timings, density of traffic lights, erratic driver behaviour, all manifest as work processes in my mind.

Yes, I am that tragic.

A consistent, SAFE, 20 mph in the city is not something that is going to majorly impact your journey from A to B. Operations Management tells us this and indeed, knowledge of this also helps with my 20mph zen like calm. Early research into the 20mph change has confirmed this state of affairs – journey times are just 45 seconds longer. The “problem” of inner city driving comes from the amount of stops and waits that fill our journeys and those are largely created by traffic lights.

As I sit on a major road which, in peak times, traffic lights reduce the amount of time that they are green, I seethe, because this increased stopping and starting of different traffic flows is not going to help to ease the congestion, it will make it worse, because you are effectively reducing the “capacity” (really throughput) of the road by exacerbating the variety of speeds travelled within the flow as cars need to slow down and speed up to and from the traffic lights. Better to keep the lights on green for longer to enable the flow to move in such times.  Turning them red and green more regularly in shorter intervals feels like it’s the right thing to do, but it’s actually more problematic for everyone’s journey time. It increases the variation in speeds and reduces the ultimate flow.

Good operations management likes reducing variation in order to affect better flow.  It’s why in peak times motorways start trying to keep everyone at a consistent 50 mph say to enable better throughput.

Good operations management also likes slowing things down at times in the pursuit of quality.  A quality focus is essential in achieving lean lead time reduction because we can only ultimately deliver process speed when we are OBSESSED with the quality of what we do at every stage. If we don’t worry about quality and speed things up regardless, we’ll meet all manner of process problems, rework and customer dissatisfaction. Slowing down the line, indeed having the ability for workers to stop the line completely (andon) so that they can sort out the quality problems FOR GOOD is a fundamental part of the ultimate “speeding up” process. This phenomenon is counterintuitive.

It’s not just ‘lean’ that recognises the importance of sometimes slowing things down.  One of the “focussing steps” of Goldratt’s Theory of Constraints tells us to do exactly that – ‘subordinate everything to the pace of the constraint resource’.  The throughput of the entire workflow will only ever be able to move at pace that the bottleneck resource allows. Ergo, you might as well make every step in the process work to that speed to try to alleviate the queues at the bottleneck.  E.g. if an MRI scanner can only scan 20 patients a day (no idea how many is logistically possible btw) then you will only ever diagnose 20 patients a day. FACT. There is no point seeing 50 patients who all require MRI scans, you might as well only see 20.   As soon as you see 50 and you can only process 20, a queue begins to form.  In this tiny example you can see how critical capacity, operation time, waste and throughput is to successful healthcare flows. (And OF COURSE you have to see the 50).

Much more impactful to a journey time is the removal of a motorist’s lane (capacity) by turning it into a bus lane or a two way cycle track.  (I’m not knocking these things, they are essential in trying to encourage active travel) but the often halving of capacity with such transformations has a massive impact on your throughput and therefore journey time, much more than travelling at 20 mph will ever have.  Imagine too the impact of a broken MRI scanner.

Whilst firmly on the 20mph’s side, I am not on the Brynglas tunnel’s however. Whilst I completely understand the environmental destruction that would be caused by the building of a relief road, how we need to turn to more sustainable forms of transport such as trains to help address the climate crisis, as I wait for 50 minutes in a traffic jam simply because seemingly someone decades ago declared “meh, it’s only Wales, why would they need three lanes of motorway?” (I’m sure it was more complicated than that) I am always reminded of the Theory of Constraint’s ultimate lesson. You can make the bottleneck (tunnel) as efficient and effective as it can be (no stopping, no lane changes etc), you can make everything travel at the pace that the bottleneck allows (speed restrictions pre tunnel), but ultimately, you’ll never solve the problem until you increase capacity at the bottleneck resource (make the tunnel bigger and add more lanes – not possible as I understand it, or build another road around the hill).

So anyway, going back to the 20mph outrage, it provides another useful change reflection point for me.  Even though what you are trying to achieve makes COMPLETE sense, that doesn’t mean that everyone is going to be on board with that change particularly if that change makes them feel that they have lost control and are now BEING TOLD WHAT TO DO.  So how do we get the anti 20 mph people of Wales to listen and understand? Some kind of mass participation in a lean simulation?! Time will undoubtedly help … people will probably just get used to it, nay, they might even perhaps reflect that it hasn’t has as dramatic an impact as they had feared. Be gads, maybe it will even make their lives better.