How to solve traffic jams - Jonas Eliasson

Hi, I'm here to talk about congestion, namely road congestion. Road congestion is a pervasive phenomenon existing in basically all of the cities all around the world, which is a little bit surprising when you think about it. I mean, think about how different cities are. You have the typical European cities with a dense urban core, good public transportation, mostly not a lot of road capacity.

But then on the other hand, you have the American cities. It's moving by itself. Okay, anyway, the Americans say there's lots of roads, dispersed to large areas, almost no public transportation. And then you have the emerging world cities with a mixed variety of vehicles, mixed land-use patterns, also rather dispersed but often with a very dense urban core.

Traffic planning all around the world has tried lots of different measures: densities or dispersed stages, lots of roads, lots of public transport, lots of bike lanes, more information, or lots of different things. But nothing seems to work. But all of these attempts have one thing in common: they’re basically attempts at figuring out what people should do instead of the rush-hour car driving. They're essentially two-point attempts at planning what other people should do, planning their life for them.

Now, planning a complex social system is a very hard thing to do. And let me tell you a story. Back in 1999, when the Berlin Wall fell, an urban planner in London got a phone call from a colleague in Moscow saying, "Hi, this is Vladimir. I'd like to know who's in charge of London's bread supply."

And the urban planner was like, "What do you mean, who's in charge of it? I mean, no one is in charge." "Oh, but surely someone must be in charge. I mean, it's a very complicated system. Someone must control all of this." "No, no, no, one is in charge. I mean, it basically organizes itself."

It organizes itself! That's an example of a complex social system which has the ability to self-organize. And this is a very deep insight. When you try to solve really complex social problems, the right thing to do is most of the time to create incentives. You don't plan the details, and people will figure out how to adapt to this new framework.

Let's now look at this: how can we use this insight to combat road congestion? This is a map of Stockholm, my hometown. Now, Stockholm is a medium-sized city, roughly 2 million people, but it has lots of water. And lots of water means lots of bridges—narrow bridges, old bridges—which means lots of road congestion.

These red dots show the most congested parts, which are the bridges that lead into the inner city. Then someone came up with the idea that apart from good public transport, or in support from spending money on roads, let's try to charge drivers one or two euros at these bottlenecks.

Now, one or two euros isn't really a lot of money; I mean, compared to parking charges, et cetera. So you would probably expect that car drivers wouldn't really react to this fairly small charge. You would be wrong. One or two euros was enough to make 20 percent of cars disappear from rush hours.

Now, 20 percent, well, that's a fairly huge figure, you might think, but you still get 80 percent left of the problem, right? Because you still have 80 percent of traffic. Now, that's also wrong because traffic happens to be a nonlinear phenomenon. Meaning that once you reach above a certain capacity threshold, then congestion starts to increase really rapidly.

But fortunately, it also works the other way around. If you can reduce traffic even somewhat, then congestion will go down much faster than you might think. Now, congestion charges were introduced in Stockholm on January 3rd, 2006. The first picture here is a picture of Stockholm—one of the typical streets on January 2nd.

The first day with the congestion charges looked like this: this is what happens when you take away 20 percent of the cars from the streets. You really reduce congestion quite substantially. But well, as I said, I mean, car drivers adapt, right? So after a while, they would all come back because they sort of get used to the charges.

Wrong again. It's now six and a half years since the congestion charge was introduced in Stockholm, and we basically have the same low traffic levels still. But see, there's an interesting gap here in the time series—in 2007. Well, the thing is that the congestion charges were introduced first as a trial, so they were introduced in January and then abolished again by the end of July, followed by a referendum.

Then they were reintroduced again in 2007, which of course was a wonderful scientific opportunity. I mean, this was really a fun experiment to start with, and we actually got to do it twice in person. I'd like to do this every once a year or so, but they wouldn’t let me do that. So, but it was fun. Anyway, we followed up to see what happened.

This is the last day with the congestion charges—July 31st. You see the same street, but now it's summer. Summer in Stockholm is a very nice and light time of the year, and the first day without the congestion charges looked like this: all the cars were back again. And you even have to admire the car drivers; they adapt extremely quickly.

The first day, they all came back. And this effect—hang on—so 2007 figures look like this. Now, these traffic figures are really exciting, a little bit surprising, and very useful to know. But I would say that the most surprising slide I'm going to show today is not this one; it's this one.

This shows public support for congestion pricing in Stockholm. You see that when congestion pricing was introduced in, well, the beginning of spring 2006, people were fiercely against it. Seventy percent of the population didn't want this. But what happened when the congestion charge was there?

It's not what you would expect; people hated it more and more. No, on the contrary, they changed to a point where we now have seventy percent support for keeping the charges. Meaning that, let me repeat, seventy percent of the population in Stockholm want to keep the price for something that used to be free.

Okay, so why can't that be? Why is that? Well, think about it this way: who changed? I mean, the 20 percent of the car drivers that disappeared, surely they must be discontent in a way. And where did they go? If we cannot just understand this, then maybe we can figure out how people can be so happy with this.

So we did this huge interview survey with lots of travel surveys and tried to figure out who changed and where did they go. It turned out that they don’t know. For some reason, the car drivers are actually confident they drive the same way that they used to. And why is that?

It's because the travel patterns are much less stable than you might think. Each day, people make new decisions, and people change—and the world changes around them. Each day, all of these decisions are sort of nudged ever so slightly away from rush hour car driving in a way that people don’t even notice. They're not even aware of this themselves.

And the other question is, who changed their mind? Who changed their opinion, and why? So we did another interview survey to try to figure out why people changed their mind and what type of group changed their mind.

After analyzing the answers, it turned out that more than half of them believe that they haven’t changed their minds—they are actually confident that they have liked congestion pricing all along. Which means that we are now in a position where we have reduced traffic across this tall cordon by 20 percent and reduced congestion by enormous numbers, and people aren’t even aware that they have changed.

If they honestly believe that they have liked this all along, this is the power of nudges when trying to solve complex social problems. When you do that, you shouldn't try to tell people how to adapt; you should just nudge them in the right direction. And if you do it right, people will actually embrace the change.

And if you do it right, people will actually even like it. Thank you.