Traffic patterns are so thoroughly entrenched in our way of life that they may as well be etched into our biology. Few things are more disorienting than trying to cross the street - much less drive, in a country that uses the “opposite” side of the street. And so when Americans visit the UK for the first time, the biggest difficulty they encounter is their own habits. 

The person who moves “across the pond” may need months, or even years, to get used to the new system. But for the Swedes? They had to get used to it overnight. And they had to do so within their own country. On September 3rd, 1967, Sweden made the switch from a left-lane driving country to a right-lane country on a historic day known as Högertrafikomläggningen (H-Day, for short). 

What happened on H-Day is more than just a bizarre historical event. When we dissect the event through the psychology of social norms, it provides a unique perspective into a kind of knowledge that is rarely spoken of: collective consciousness. In doing so, it provides a jumping-off point for understanding how and why social systems break down and descend into anarchy - even when traffic patterns stay constant. 

So how did this sudden shift of habits go? And what can it teach us about social norms? 

Let’s Dive in. 

Sweden’s Historic Traffic Shift  

Early on September 3rd, from 1a - 6a, no cars were allowed on the road in the entire country. During this period, the road signs in the entire country were changed to the new system. When the country woke up and hit the road, it was officially a right-lane driving country. 

The country had prepared well in advance for the change, investing millions of dollars in public communications. Not wanting anyone to be caught off guard, The Swedish government went to extreme lengths to get the word out - they even created an H-Day logo which was prominently displayed on billboards, milk cartons, and even on specialty underwear. The impending traffic switch was impossible to miss. 

So how did it go? 

Not well. Firsthand reports tell the story of an incredibly stressful and chaotic day on the roads. Damon Centola, a sociologist and professor at the University of Pennsylvania has studied this event closely. As described in his 2021 book, Change, “For each of the reported accidents, there were hundreds of unreported near-accidents throughout small towns and major cities.” 

Bjorn Sylven, a Stockholm resident, echoed this sentiment. He recalled the streets that day as a dangerous tumult of cars and people. “Outside my school,” Sylven told a local paper, “I saw about three times that cars veered on the wrong side, and came very close to hitting the other schoolchildren.” 

If everyone knew about the switch - H-Day underwear and all, then what was the problem? It turns out that generating awareness for the switch was the easy part. The issue wasn’t in individual knowledge, but in collective knowledge. It wasn’t an issue with individual cognition, but in social cognition. 

What Sweden’s Traffic Shift Tells Us About Social Cognition and Social Norms

The primary issue with the traffic switch was one of collective doubt. As Damon Centola describes, “The problem was not that people did not know what to do..The problem was that people did not know what other people were going to do.” What Centola is describing is a key element of social cognition: the process by which we automatically model another person’s internal experience. 

A huge part of this is modeling their understanding of the social norms. These are the codes of conduct and generally accepted behaviors that are crucial for social interaction. For driving, these are mostly incorporated into the law; the “rules of the road” that all drivers learn to get their license. This is great for driving, but most of life isn’t like this. There aren’t set rules for how you should act and what you should do. 

When you meet someone for the first time, there’s no law saying you need to shake their hand and make eye contact. When someone has a loved one pass away, there’s no law obligating you to offer your condolences. And of course, in these scenarios and many others, the social norms differ dramatically across different cultures. 

For the vast majority of our interactions, there aren’t set laws or rules - all we have is our social norms. 

Social Norms and Social Coordination in Sweden’s Traffic Switch

So how did all of this play out during Sweden’s traffic switch? It’s important to simply know the social norms of the society in which one lives. But here’s the thing: it's even more important to have confidence that other people know them. This is what holds society together. 

Michelle Gelfand of Stanford University has spent decades studying social norms. In her seminal book entitled, Rule Makers, Rule Breakers, she distills this perfectly, “Social norms are the glue that holds groups together; they give us our identity, and they help us coordinate in unprecedented ways.”

Now imagine these dynamics at play while driving. You’re driving a car in the early morning of H-Day. You know it’s H-Day, and that you should be driving on the right side of the road. But what happens when you encounter another car on the road? Now doubt creeps in: Do they know that they’re supposed to be driving on the right-side of the road? 

From what we know of H-Day, this is exactly what happened on the roads that day. When we lose confidence that others are on the same wavelength, disaster looms - society loses its glue, and in turn, we lose the ability to coordinate with one another. 

From Social Norms to Collective Consciousness

Another way to think about these kinds of coordination problems is as a failure of “collective consciousness”, a term popularized by one of the original pioneers of sociology, Emile Durkheim. His idea is that there is a certain knowledge that doesn’t just exist within individual people, but within the society they live in. 

This includes, crucially, social norms. When you meet someone for the first time, you shake their hand and tell them “Nice to meet you”. If someone is blocking your path, you say “Excuse me” and they let you pass. As Gelfand distills, 

“As children, we learn hundreds of social norms—for example, to not grab things out of other people’s hands; to walk on the right side of the sidewalk (or the left, depending on where you live); to put on clothes each day. We continue to absorb new social norms throughout our lives: what to wear to a funeral; how to behave at a rock concert versus a symphony; and the proper way to perform rituals—from weddings to worship.” (p. 3)

In this way, society itself generates a kind of collective knowledge, which brings it together as a coherent system. A city isn’t just a random collection of people bouncing off one another; it’s a coherent community held together by a shared understanding and identity. There are no hard and fast rules about any of this. This knowledge is learned, and each society has its own corpus of unspoken rules and social overtures. 

If a society is more than just a collection of people awkwardly bouncing off one another, in pursuit of their idiosyncratic interests, it has its collective consciousness to thank. 

Final Thoughts on Social Norms and Anomie

Social norms are dynamic systems, and they naturally shift over time. But these are typically slow evolutions - they don't literally happen overnight. 

What H-Day teaches is that it’s not enough to merely be aware that these norms are shifting. You don’t just need to understand the norms - you need to understand that other people know the norms, and that they, in turn, know that other people know the rules. This is the very essence of a social norm - the unspoken level of understanding between people, which enables large groups of people to cohere and coordinate. 

In the case of H-Day, the individual awareness was there, but what was missing was this all-important collective awareness. Thankfully, the consequences were relatively minor. The fraying of social norms was confined to the arena of driving, where, aside from a few dented bumpers, the consequences were relatively minor. 

But this isn’t always the case. There are hundreds of social norms which we, as a culture, understand implicitly, and which enable us to coordinate and cohere. 

What happens when these broader social norms begin to fray? Or as Durkheim would phrase it, what happens when society loses its collective consciousness? These are questions that Durkheim himself thought a lot about. He had a specific name for a society that descends into this normless state: anomie. 

Durkheim coined this phenomenon back at the turn of the 20th century, as European society was undergoing immense upheaval. Over 125 years later, we’re witnessing a similar shift in social norms - especially in the digital world. What is anomie and what is behind its resurgence? Continue on in Part 2

Photo by Johannes Blenke via Unsplash

References for The Psychology of Social Norms on Sweden’s H-Day

Centola, D. (2021) Change: How to Make Big Things Happen, Penguin Press

Enqvist, T. (1996). Pressdebatten om högertrafikomläggningen.

Gelfand, M. (2019). Rule makers, rule breakers: Tight and loose cultures and the secret signals that direct our lives. Scribner.