Dwelling on dwell time

I have written two posts on dwell time this week. One on Clyde Street (link) and one for the Sports Wizard blog (link).

I have continued to research dwell time in non-sport contexts. The discovery of Herbert Levinson’s (1983) paper has been very influential in directing my literature searches.

In his paper, Herbert conducted an analysis of transit speeds, delays, and dwell times based on surveys conducted in a cross section of U.S. cities. He concluded that “reducing bus stops from eight to six per mile and dwell times from 20 to 15 sec would reduce travel times from 6 to 4.3 min/mile, a time saving greater than that which could be achieved by eliminating traffic congestion”. He added “transit performance should be improved by keeping the number of stopping places to a minimum”.

I have been thinking about how to visualise stoppages in play in sport. Two of the papers that cite Herbert’s paper offer some insights on how this might be done.

Robert Bertini and Ahmed El-Geneidy (2004) provided a case study of how this visualisation might occur with their estimation of “the values of parameters that affect the total travel time for a particular bus route in Portland, Oregon”. In doing so they shared a trip time model.

Their visualisation of dwell time included:

Mathew Berkow and his colleagues (2007) used colour in their visualisations of transportation in Portland:

Mathew and his colleagues conclude “On the basis of an analysis of 1 year of archived bus dis-patch system data for all routes and stops, the power of using visualization tools to understand the abundance of bus dis-patch system data is demonstrated. In addition, several statistical models are generated to demonstrate the power of statistical analysis in conveying valuable and new transit performance measures beyond what is currently generated at TriMet or in the transit industry in general. It is envisioned that systematic use of these new methods and transit performance measures can help TriMet and other transit agencies improve the quality and reliability of their service”.

These formative discussions about dwell time have really encouraged me to think about pedagogy in sport as well as officiating. In my next dwelling on dwell post I am going to look at referee behaviour at the 2018 FIFA World Cup and the 2019 Asian Cup. It is, I hope, the kind of detailed observation of performance that Herbert, Robert, Ahmed, Mathew and his colleagues might have found interesting.

Photo Credit

Photo by Scott Walsh on Unsplash

Ball not in play

Ray Williams’ book Rugby for Beginners was published in 1973. I first read it as a postgraduate physical education student at Loughborough College. By coincidence, Ray had been a student there too. Both of us were from North Wales.

Years later when I got to know Ray, I was able to explain how important the book was to me in my development as a player, teacher and coach.

The cover of Ray Williams' book.

Huw Richards (link) wrote about Ray’s career and noted his appointment as the Welsh Rugby Union’s first national coaching advisor. In that role he “drove that transformation through his promotion of conferences, teach-ins and courses which gave Wales more than 300 qualified coaches by the mid-1970s”.

I was fortunate to be one of those coaches and delighted in late night conversations with Ray in the bar of the National Sports Centre at Sofia Gardens in Cardiff. It was like being with the Oracle at Delphi.

One conversation became quite heated. I asked Ray about a line in his book that suggested “no player has the ball in his hands for more than one minute” in a game. The essence of Ray’s argument was that each player had a responsibility to support the ball (one of Ray’s game principles).

Even at my time playing rugby at Loughborough, I was sure I did not have the ball in my hands for that amount of time. I suggested to Ray that I ought to investigate what time the ball was in play and not in play.

I did follow up on this for the much of the next two decades. My operational definition of ball in play time was when the game was started and restarted by the referee either by a whistle or when the play was put back into play. Ball out of play was measured by a referee’s whistle or when the ball visibly left the field of play or was waiting the restart of the game.

It took some time to stabilise the recording of ball in play time. I monitored ball in play time from live broadcasts. One of my first successful attempts was on 16 January 1982, in what was then the Five Nations rugby tournament. Scotland played England at Murrayfield in a game refereed by Ken Rowlands (Wales).

  • The first half game time was 42 minutes and 33 seconds. The ball was in play for 10 minutes 28 seconds.
  • The second half game time was 44 minutes. The ball was in play for 13 minutes 10 seconds.
  • In the whole game, the ball in play time was approximately 27% of the available time.

It took me a further three years to develop a template to record each passage of ball in play in real time in addition to the other data I was collecting with hand notation. From this time on I termed passages of ball in play activity cycles.

My record of the Scotland v Wales game played on 2 March 1985 (video link) was:

For the first time, I was able to have a detailed account of game play. I recorded 97 distinct activity cycles (49 first half, 48 second half). Scotland had 52 of these (25 first half, 27 second half) and Wales 45 (24 first half, 21 second half). The game was refereed by Rene Hourquet of France. Wales won 25 points to 21 points.

The activity cycles were:

My record of the 97 activity cycles indicates a total ball in play time of 25 minutes 46 seconds (12 minutes 01 seconds first half, 13 minutes 45 seconds second half). Scotland had 13 minutes 20 seconds of ball possession and Wales 12 minutes 26 seconds.

I shared these data with Ray and we corresponded about the implications of such data for coaching and playing. I continued to share my data with him and he in turn passed it on to colleagues in coaching.

I have returned to these data this week as I researched the concept of dwell time (link). I was delighted to discover that Herbert Levinson (1983) was undertaking similar real-observations of performance … in the context of transit travel times. He concluded “transit performance should be improved by keeping the number of stopping places to a minimum”. That sounds like a fascinating pedagogical insight for rugby union.


Scoring first and not losing in association football

A bar chart of probabilities of scoring first and not losing in six European football leagues

After this week’s games in six European football leagues, it is interesting to see how each league is tracking against a prior probability of scoring first and not losing.

I established the priors from results in the 2017-2018 season. Two of the six leagues (Bundesliga and Eredivisie) are different to their priors in comparison to four other leagues (EPL, Ligue 1, Serie A and Primera).