Category Archives: Soapbox

Pareto principle in train travel

The moral of this story is don’t travel with me.  Last week, I wrote about my train being delayed by someone pulling the emergency handle before we got to the end of the platform in Liverpool [see ‘Stopped in Lime Street’ on June 26th, 2019].  Four days later, I was once again on a late afternoon train to London waiting for it to leave Lime Street station.  This time we didn’t even get started before the train manager announced that a road vehicle had hit a bridge between Crewe and Liverpool; and, so we were being held in Liverpool for an unknown period of time.  I sent a message to my family telling them about the delay and one, an engineer, replied that I was ‘hitting the low frequency failure modes on the service quality pareto’.  The Pareto principle is also known as the 80/20 principle.  I first encountered it when I was working at the University of Sheffield and the Vice-Chancellor,  Professor Gareth Roberts, used it to describe the distribution of research output in academic departments, i.e., 80% of research was produced by 20% of the professors.  In service maintenance, it is assumed that 80% of service interruptions are caused by 20% of the possible failure modes.  Hence, if you can address the correct 20% of failure modes then you will prevent 80% of the service interruptions, which is an efficient use of your resources.  The remaining, unaddressed failure modes are likely to occur infrequently and, hence, can be described as low frequency modes; including passengers pulling emergency handles or people driving vehicles into bridges.

How do you drive into a bridge and block the main railway lines between London and the north-west of England?  Perhaps the driver was using their smart phone which was not smart enough to warn them of the impending collision with the bridge.  So, there’s a new product for someone to develop: a smartphone app that connects to dashboard camera in your vehicle and warns you of impending collisions, or better still just drives the vehicle for you.  Yes, I know some vehicles come with all of this installed but not everyone is driving the latest model; so, a retro-fit system should sell well and protect train passengers from unexpected delays caused by road vehicles damaging rail infrastructure.

By the way, the 14:47 to London magically became the 15:47 to London and left on time!

Stopped in Lime Street

It is a late, slightly muggy, summer afternoon and I am sitting at the window in the last carriage of a train waiting for it to leave Liverpool for London.  So far, it has been a busy day with meetings in the morning at the University’s facility at Daresbury followed by a couple on the main campus before I walked down to Lime Street station.  I stopped for a bite to eat as I travelled from Daresbury to Liverpool; but I am hungry again, so I have a sandwich that I bought in the station.  However, I don’t like to unpack and start eating until the train starts moving, just in case I am on the wrong train or we have to change trains.  Finally, the train starts to move and as it builds up speed I reach for my sandwich.  Suddenly it stops.  My carriage has not even reached the end of the platform.  Station staff appear outside my window talking into their radios.  What’s happened?  Did the train hit someone?  I thought there was a small thud just before we stopped.  But the station staff seem unflustered.  Wouldn’t there be more urgency about their movements if there was a casualty?  We sit in silence for ten minutes before the train starts to move again and the train manager announces that someone pulled the emergency handle because they decided that wanted to get off the train. Why did they want to get off the train?  Did they realise they were trapped on the train to London with someone who was pursuing them?  Was it a police officer who realised that their quarry had jumped off the train just before it set off?  Or, have I been reading too many Eric Ambler stories (see ‘The Mask of Dimitrios‘ or ‘Journey into Fear‘) involving train journeys across Europe?  Maybe it was someone who just decided that they didn’t want to go London after all and didn’t care about inconveniencing several hundred people or paying the fine for improper use of the emergency handle.  But that seems unlikely too or perhaps not…  I contemplate these options as the train accelerates towards London and I munch my sandwich.  It reminds me of a quote from Gillian Tett (in the FT Weekend on June 17/18, 2017) about people believing they have a ‘God-given right that they should be able to organise the world around their personal views and needs instead of quietly accepting pre-packaged options’.

Meta-knowledge: knowledge about knowledge

As engineers, we like to draw simple diagrams of the systems that we are attempting to analyse because most of us are pictorial problem-solvers and recording the key elements of a problem in a sketch helps us to identify the important issues and select an appropriate solution procedure [see ‘Meta-representational competence’ on May 13th, 2015].  Of course, these simple representations can be misleading if we omit parameters or features that dominate the behaviour of the system; so, there is considerable skill in idealising a system so that the analysis is tractable, i.e. can be solved.  Students find it especially difficult to acquire these skills [see ‘Learning problem-solving skills‘ on October 24th, 2018] and many appear to avoid drawing a meaningful sketch even when examinations marks are allocated to it [see ‘Depressed by exams‘ on January 31st, 2018].  Of course, in thermodynamics it is complicated by the entropy of the system being reduced when we omit parameters in order to idealise the system; because with fewer parameters to describe the system there are fewer microstates in which the system can exist and, hence according to Boltzmann, the entropy will be lower [see ‘Entropy on the brain‘ on November 29th, 2017].  Perhaps this is the inverse of realising that we understand less as we know more.  In other words, as our knowledge grows it reveals to us that there is more to know and understand than we can ever hope to comprehend [see ‘Expanding universe‘ on February 7th, 2018]. Is that the second law of thermodynamics at work again, creating more disorder to counter the small amount of order achieved in your brain?

Image: Sketch made during an example class

Only the name of the airport changes

The conference that I attended last week was in Reno, Nevada and, on my way to it, I stopped over in Dayton, Ohio and visited the US Air Force Research Laboratory to present the results from our research project supported by their European Office of Aerospace Research & Development (EOARD).  The journey from Liverpool to Dayton, via Manchester and Altanta airports, took 17 hours; however, that was short compared to the journey from Dayton to Reno, via Chicago and San Francisco airports, which took 24 hours door-to-door or rather hotel-to-hotel.  ‘Only the name of the airport changes’ is a quote from Italo Calvino describing the city of Trude in his book ‘Invisible Cities‘; but it also described how I felt looking out from my window seats at successive airports over the four days that I travelled from Liverpool to Reno.

We arrived at Dayton airport at 5am for a 7am flight to be told that it was cancelled and we were re-booked on a flight leaving at 5.18pm.  We tried to re-rent the rental car that we had just returned but were told every car was booked; so, we were stuck in Dayton airport for 12 hours.  Your perspective of time changes in these circumstances.  At 5am with nothing much to do, 12 hours seemed like infinity; but at 5pm when we were about to board our flight, the same 12 hours seemed short – almost as if we had only arrived at the airport an hour or so earlier.  Augustine observed that our consciousness is based on memory and anticipation such that time is entirely present in our minds as memory and as anticipation.  While Aristotle considered time to be the measurement of change.  Hence, since I was anticipating no change during my 12 hours of waiting, my perception of time was of it passing very slowly.  Whereas, when I was boarding my flight 12 hours later, my memory was of having done the same things that I would usually have done while waiting for a flight [reading and editing draft manuscripts from my research group]; and hence my perception of the elapsed 12 hours was compressed into the usual 2-hour period spent at an airport prior to a flight.  The apparent unchanging view out of the plane’s window, both in flight and, to a lesser extent, on the ground also tended to distort my perception of the passage of time.


Italo Calvino, Invisible Cities, Penguin Vintage Classics, 1997.

Carlo Rovelli, The Order of Time, Penguin, 2019.