Picture of Lawrence LohLawrence Loh is an Adjunct Professor at the Dalla Lana School of Public Health at the University of Toronto


I took up run-commuting following the birth of my first child because leisure time physical activity just wasn’t going to happen. My office had a shower, and what better way to counter the drudgery of the commute? I soon discovered mental calisthenics were also part of the running deal—not only in planning logistics, like ensuring you have enough toiletries, underwear, and the right accessories at the office—but also in the opportunity to sharpen one’s sense of observation.

The routine of run commuting leads one to notice patterns over time. If you leave at the same time most days, you can gauge whether you’re on time by watching where buses and trains arrive around you—assuming they’re also on time, of course. And running the same route allows you to notice details and changes in the neighbourhoods you cross—the same people walking the same dogs, the same cars scurrying to appointments, or the hole in the ground turning into a brand-new building.

Surrounded by so many different things to observe, a physician scientist can very easily head down a rabbit hole in applying the scientific method to their observations. During one of my runs a simple glance turned into a series of hypotheses to help me to get to the bottom of garbage day.

Out with the trash

Sidewalks in my part of Toronto are already narrow; navigating them requires a certain courtesy towards families, walkers, caregivers with strollers. And then there are these garbage bins that come out once a week. Ever-observant as I run, one garbage day I noticed what seemed to be serial numbers on the front of the garbage bins, of the format NN L NNNNNN (N = number, L = letter.)

Channeling Karl Popper, I started my observations, trying to determine a trend. The bins on this block seemed to come in two sizes – one for garbage, one for organic waste. I focused on the black garbage bins and noted that the format was consistent (they all had the same NN L NNNNNN) and the first two numbers seemed to be the same over at least six bins on this block – in this case, 35.

My first hypothesis was thus: perhaps this block received the same series of bins? Jogging across the road and on to the next block, the first bin I encountered was noticeably larger than the previous six. And the first two numbers for this one were also different: reading at 95. A stream of regular sized bins followed on the rest of the block, all with a 35.

I refined my hypothesis: the first two numbers represent the capacity of the bin. Perhaps in litres – 35 L for a regular sized bin; 95 L for the monster. As with any good scientific theory, it was time to test this new hypothesis. A smaller bin was coming up. First two numbers – 18. Bingo! I was in business. Over the next few blocks, the numbers popped up on a regular basis and I soon determined there seemed to be four main sizes – 18, 35, 65, and 95 L bins… at least for garbage.

The first two letters out of the way, I ducked through a pedestrian crossing and headed onward through a new, leafy neighbourhood, now wondering – what might the letter mean? Could it also have a meaning, or was it simply random? Given that the first two numbers had a pattern, I felt it fair to hypothesize that the letters also represented something… but what specifically?

I considered the garbage bins again as I jogged by – all of them had a “G”. So 35G, and 95G, and on it went. Find another observation series to prove or disprove – ah, let’s look at the green organics bins also hanging out. And sure enough, an O instead of a G led me to decide that the letter likely meant the type of bin – presumably G for garbage, O for organics.

Now did this hold up with the recycling bins as well? Given that Toronto alternates garbage and recycling fortnightly with organics going out weekly, it took a few hundred more metres before I came across a recycling bin to triangulate my observations. The one recycling bin out in front of this house – perhaps the owner was out of town – confirmed that indeed, the letter was R, which meant I was now three of nine characters out of deciphering this bin code that I’d chanced upon. How delicious!

One person’s trash is another’s treasure

On to the last challenge – what might the last six digits represent? Presumably, this is where the series would come through.

If one assumed that the last six digits were a unique identifier for each bin, then we could assume that nearly 1 million possible numbers for each category of bin capacity and type (e.g. one million 35L garbage bins?)

I became curious about how I might use this information to figure out the maximum possible amount of household waste the City of Toronto produces. At this point, I realized I would likely need to reference other data. It would be a matter of combining how many households are in Toronto—likely in a registry somewhere—and what proportion of those houses have which types of bins. Taken in aggregate, one could get an estimate of that maximum capacity for household waste by type.

This led to my run-commuting physician scientist’s brain looking at proportions over ten-bin counts. Over the next few blocks, at least for garbage, I tried to figure out what proportion of houses had each size of bin. Over four cycles of ten, each ten seemed to have 1 of each of the extremes (an 18L and a 95L), 2 of the 65L, and 7 of the 35L “standard” that had started this whole quest in the first place. I did note, however, that the share of 95L bins increased the further out into the ‘burbs my run commute took me. I tried to justify the idea that this might be a reasonable way to estimate total capacity if there wasn’t another more accurate data set (such as a registry of bins) to refer to.

All told, though, counting out those cycles also allowed me to get a bit closer to the meaning of the last six digits. There was one block where those six numbers were all separated by a single unit (e.g. 980201, 980202) – so the easiest hypothesis at that point was to imagine that this was a serial number and that these were cohorts that had been distributed at the same time from the same lot. All this from simple running, observation, and a in inquiring mind—and importantly, as with any aspect of the scientific method, a willingness to reframe my hypothesis.

Then, one final twist as I got close to my office: I noticed a final garbage bin in the nearby public park. A serial code with the letter “P” led to further refinements of the hypothesis… perhaps P stood for either “park” or “public”. Another change in pattern, accounting for new information, and hypothesis refinement. The essence of Popper’s method.

Land-filling in the details

On getting to the office, I did what any good scientist would do—I attempted to verify my findings with established literature. I learned that, yes, the first two numbers and letter indeed identify the type and capacity of the bin. (1) I also learned that the “regular sized” bins (labelled 35G) are great value – which might explain why they were the most commonly observed bin on the street. (2)

I learned also that the 35 was for gallons, not litres, and that the capacity of these bins was closer to 120 L. In jotting this experience down, I have surprised even myself that a simple observation could have led to the development of such a robust hypothesis. I also realize that the knowledge I’ve now added from this exercise is not so useful—unless I’m looking to exchange my bins in the future; the City’s website will need my own numbers then.

Lest you think this reflection is just garbage let it remind you, as it reinforced for me, that, as physicians, we must continue to apply rigour and critical thinking continuously to the evidence and observations we encounter in our day to day practice. Particularly in this world filled with “fake news” and conspiracy theories.

I’ve reaffirmed my own commitment, and am looking forward to many future run commutes where I can jog both my legs and my critical thinking juices.