Finding the Hidden Social Networks of Public Transit

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There’s something romantic about the city.

You’ll find yourself amid the anonymous bustle of strangers, sitting in a café, or riding the metro — when one of those strangers will catch your eye.

In a city with so many beautiful people, encountering an interesting stranger isn’t that uncommon. But every now and then, one of those strangers will catch your glance, look back — and smile.

It’s a small rush, but enough to make your day. They’re fleeting encounters, shared with people you never expect to see again.

But what if we told you that many of those so-called “strangers” you see every day weren’t actually strangers at all?

In 1972, the man behind the infamous “shock experiment”, psychologist Stanley Milgram, decided to explore something less insidious: the hidden links between strangers.

Milgram defined a familiar stranger as someone who we:

1. observe
2. observe repeatedly
3. never interact with

Familiar strangers are people we encounter often, but ignore. Even in enormous cities, our regular routines have us running into them all the time.

But while the “concept” of familiar strangers is interesting, it’s rather difficult to quantify. Still, we wondered: is it possible to retrace the steps of an entire city to figure out who met who?

Yes — it is.

Transit Presents: Montreal’s Familiar Strangers

Our study begins with a sample of Montreal’s transit data. The data spans 10 weekdays, 2 million commuters, and 18 million trips. It was released by the STM for a hackathon in 2011, and contains anonymized data of every single tap for every single fare card.

But that data was useless without context. Then, a few weeks ago, one of our friends found a copy of the 2011 schedules on his hard drive. (Some people store travel photos on their hard drives, other people store transit schedules… to each their own 🙂

By comparing trip data to transit schedules, we could now reconstruct the complete transit history of Montreal.

For the purposes of our study, we consider a familiar stranger to be someone you see at least once a week, assuming you take the same bus every day.

Here’s what we found:

Do You Come Here Often?
Route 55: Saint Laurent

If you don’t live in Montreal, you should know that Saint Laurent Boulevard is Montreal’s most famous street. It’s a North-South thoroughfare that has traditionally divided Montreal’s Anglophones (to the West) from its Francophones (to the East).

Its nickname is “The Main”. It cuts through Montreal’s most famous neighbourhoods (like the Plateau and the Mile End), and hosts restaurants like Schwartz’s (which serves up Montreal’s legendary smoked meat sandwiches), and bars like Casa del Popolo (where Arcade Fire launched their first EP).

In this graph, displayed in orange are the total passengers on one bus at any particular time. The other colours represent familiar strangers. In the case of Saint Laurent’s 55 bus, you are most likely to encounter a familiar stranger during the morning rush hour, when you might recognize as many as half the people on your bus.

If you take the 8:15 bus every weekday, there are more than twenty people who you would encounter at least once a week.

We calculated the number of familiar strangers for every bus in Montreal. Below, we analyze the familiar strangers on four of Montreal’s most interesting routes — but if you’re impatient, you can click here to look up your own route.

The Airport Shuttle
Route 747: Trudeau Airport — Downtown

Montreal’s humorously named 747 bus travels from downtown to the airport in Dorval. Most familiar strangers on the shuttle see each other around 6 and 7am — even though the total number of trips is highest in the afternoon.

That’s probably because the “familiar strangers” running into each other on the bus are fellow workers arriving at the airport for their morning shifts. It’s unlikely that a tourist will regularly take the shuttle, and it’s hard to imagine anyone besides an airport worker travelling to the airport at the same time, week after week.

The Drunk Bus
Route 361: Saint-Denis

If you’ve ever stayed out until the wee hours of dawn, drinking pints of Boréale on Saint Denis Street, the 361 has probably helped you get home. Metros in Montreal close at 1 am, and so do many bus lines. The 361 fills in by providing all-night service after 12am, and runs buses every four minutes when bars let out at 3am on weekends.

Besides carting Saint Denis’ inebriated revelers back to their beds, the 361 is also relied upon by service industry workers to get home after their shifts end. That’s perhaps what explains the surge in familiar encounters around 04:00 — an hour after last call. At that point, the bars have been emptied and cleaned, and fellow workers begin to head home on the same buses.

Since only weekday data was used for our analysis, the crowding levels here are lower than what you’d expect on a weekend.

Your Part of Town Against Mine
Route 105: Sherbrooke vs. Route 215: Henri-Bourassa

The suburbs may be boring, but they’re surprisingly familiar. Here’s why:

If your bus comes every half hour, it’s more likely that you’ll take the same bus every day. However, if it comes every ten minutes, you could end up on one of several buses — lowering the odds of seeing the same people on it, week after week.

The 105 (serving downtown, along Sherbrooke) is part of the STM’s “10 minute max” network, which means that during weekdays, a bus will come every ten minutes, or less. However, the 215 (serving the suburbs of Pointe-Claire) come much less frequently. Riders of the suburban line are thus much more likely to encounter familiar strangers.

Another difference between the 105 downtown bus and 215 suburban bus is the big boom in familiar encounters on the afternoon 215. Perhaps suburban commuters, who often have families and live farther away, follow a more regular routine in the afternoon, which begets more familiar encounters.

They might be expected home at a certain time in order to run errands, or to take their kids to ping pong practice. But with amenities nearby, downtown commuters have the flexibility of doing more than just “heading home” when they get off work — they could get groceries on their way, or choose to sling back a couple of whiskeys with colleagues at a 5-à-7.

Bridging The Gaps

We all lead our own separate little lives, but remain connected to the rest of the city through our shared reliance on public transit. But while we’re constantly running into familiar strangers, our ties to them are weak and rarely progress beyond that.

There is a certain expectation when riding public transit to keep to yourself. We tend to avoid eye contact, play with our phones, and wear ostentatious headphones — signalling to fellow passengers that we’d rather be left alone. Should that change?

Well, contrary to our intuitions, when people go outside of their comfort zone and engage in small talk with fellow passengers, they not only end up feeling happier afterward, but strangers are often more than happy to entertain a conversation.

You might recall memories of riding the bus home after a long day of classroom drudgery — it was a chance to catch up and socialize with friends.

Of course, things are a bit different when you’re riding with strangers, but researchers have found that when we talk with people we don’t know, it actually makes us feel just as happy as when we interact with our friends.

With strangers, we try to put on our best face in order to make a good first impression. We aren’t as quick to indulge our grumpier thoughts — and that’s a good thing. In fact, the subconscious effort to appear friendly makes us feel better about ourselves. That’s why we find friendly encounters with a cashier, barista, taxi driver — or, heaven forbid, a stranger on the metro — so pleasant.