喬納斯艾歷森：如何解決塞車問題

嗨，我今天要談的是塞車 也就是所謂的交通擁塞 塞車非常普遍 世界各地的城市都有這個問題 仔細想想其實令人驚訝 畢竟城市之間不同之處甚多 像典型的歐洲城市 都有稠密的都市中心，良好的公共交通 但大部分道路狹小 另一方面，我們看看美國城市 它自己動起來了，好言歸正傳，美國的城市裡 許多道路散佈在大片土地上 幾乎沒有公共交通工具 再來是初嶄頭角的世界級城市 當中混雜各種交通工具 各種土地使用模式，而且相當分散 市中心卻多數人口稠密 世界各地的交通規劃人員 採用過不同措施：以密集或分散形式規劃城市 建大量道路，或大力發展公共交通 規劃很多單車徑，或提供更多資訊 措施不勝枚舉，但似乎都不得要領

這一切努力都有一個共同點 就是嘗試找出 人們避免在尖峰時間開車的方法 基本上這些方法旨在影響人該做什麼 替別人規劃生活

規劃一個複雜的社會系統相當困難 讓我給你說個故事 早在1989年，柏林圍牆倒下時 一位倫敦的都市規劃師接到電話 是莫斯科的同事打來的，他說 “嗨，我是維拉迪摩，我想知道 倫敦的麵包供應是誰管的？”

那位都市規劃師回應道 “甚麼意思? 誰管理倫敦的... 沒人管啊。” “但總有個人管吧 這個系統極其複雜，一定要有人管理運作。”

“不，不，真沒人管 我意思是，我真的沒想過這問題 系統會自我管理吧。”

自我管理 這例子說明複雜的社會系統 擁有自我管理的能力 這洞見發人深省 當你試圖解決非常複雜的社會問題 很多時候 正確的做法是製造誘因 不需要規劃細節 大家自會知道該做甚麼如何適應這個新框架

讓我們現在看看如何應用這洞見 來解決塞車問題

這是我家鄉斯德哥爾摩的地圖 中型城市，現時大約住了兩百萬人 但斯德哥爾摩除了水還是水即是說城裡有很多橋，古老的，狹窄的 亦即是說交通經常擁塞 這些紅點代表最擁塞的區域也就是通往內城的橋 後來有人想出解決方法 不是改善公共運輸 不是大費金錢興建道路 而是在瓶頸位置向司機徵收一兩歐元

一兩二歐元不是甚麼大錢 相對於停車費和日常開支而言 所以你可能以為司機們 對這種小額收費無動於衷 你錯了 一兩歐元足以令百分之二十的汽車 在尖峰時間從路上消失 百份之二十，你或許覺得這是個大數字 但仍有百份之八十的問題未解決，對嗎？ 因為仍然有百份之八十的汽車在路上 這也是錯的 因為交通問題不是綫性現象 當你超過一個容量臨界點之後 交通擁塞會開始很快地惡化 幸運的是，反之亦然 如果你可以稍為減少交通量 擁塞問題減輕的速度比你想像中更快 道路收費於2006年1月3號在斯德哥爾摩實施 這裏第一張是斯德哥爾摩 一條典型街道的照片，在2號拍的 開始收費的第一天它變成這樣 這就是路上減少百分之二十的車輛以後 看起來的樣子 實際上，塞車情況大為改善

但正如我所說，汽車司機會適應的，對嗎？ 所以不久之後，他們會回到路上 因為他們已適應了收費 又錯了，六年半前 斯德哥爾摩開始徵收道路費 到了今天，路上的汽車流量依然偏低

但大家看，在時間序列上有個有趣的間縫 時為2007年 實情是這樣的 道路收費最初引入時屬試驗性質 故此在一月引入後，七月尾便被廢除 接着舉行全民投票，然後在2007年再次引入道路費 這當然是一次極好的研究機會 我意思是開始時它已是個有趣的實驗 而我們有機會兩次進行這實驗 對我來說，我希望大約一年進行一次 但他們不許我這樣做 無論如何這是有趣的實驗

我們跟進之後，有甚麼發現？ 這是7月31日，徵收道路費的最後一天 你看到的是同一條街，而這正是夏季 斯德哥爾摩的夏季 是年中非常天朗氣清的日子 取消道路收費的第一天 是這樣的 所有汽車都返回路上，你真的要佩服那些司機 他們的反應真的很快 他們第一天就回來了情況持續下去，所以2007年的數據是這樣的

這些交通數據真的令人興奮 有點出人意表，但同時十分有用 但今天給大看的幻燈片中 最令人驚奇的不是這張，而是這張 它顯示了市民支持在斯德哥爾摩實施道路收費 你看到當引入道路收費之時 即2006年初春，人們激烈反對收費 百份之七十的市民反對收費 當道路收費實施後，出現的情況並不如你想像的那樣 人們會越來越憎惡它 正好相反，他們改變了 現時有百份之七十的市民支持繼續收費 我是說，讓我再說一次 斯德哥爾摩百份之七十的人口 希望對一樣一向可免費使用的東西繼續收費

怎會這樣？有甚麼原因？ 試循這方向想。誰改變了？ 那百份之二十消失了的司機 肯定會在某方面感到不滿 他們去了那裏？如果我們明白這點 或許便可以明白為何人們喜愛這措施 我們很多交通工具上 進行大型的訪問調查 目的是要找出誰改變了，和這些人去了那裏？ 原來受訪者自己也不知道 由於某些原因 那些司機都認為他們按自己一貫的方式駕駛 為甚麼會這樣？這是因為人們的駕駛路線 並非如你想像那般穩定 每一天，人會做新的決定，人會變 環繞他們的世界也在變 每一天這些決定會產生細微作用 促使他們避開繁忙時間駕車 人往往不會覺察這些作用 他們自己甚至不知道自己已改變

另一個問題是，誰改變了他們的心思？ 誰改變了他們的想法，和為甚麼？ 我們為此做了另一個訪問調查 為了要了解人為何改變想法，和那些群組的人改變了想法？ 分柝了數據之後，我們發現 超過一半的人認為他們的想法沒有變 他們真的以為 他們一直都喜歡道路收費 這即是說現在的情況是 我們透過收費界線減少了百份二十交通流量 同時大幅減少了塞車情況 而人們甚至不為意他們已改變了 並且他們誠實地相信他們一直都喜歡這個情況

這就是我們解決複雜的社會問題時 輕推所產生的力量，你那樣做的時候 你不應該試圖告訴人他們要如何適應 你只要輕輕把他們往對的方向推 如果你做得對 人們會支持改變 並且如果你做得對，人們甚至會喜歡它 謝謝大家。（拍掌）

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Hi. I'm here to talk about congestion, namely road congestion. Road congestion is a pervasive phenomenon. It exists 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, actually. I mean, 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 American cities: lots of roads dispersed over 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 dispersedbut often with a very dense urban core. And traffic planners all around the world have triedlots of different measures: dense cities or dispersed cities, lots of roads or lots of public transport or lots of bike lanes or 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 rush hour car driving. They're essentially, to a 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 1989, when the Berlin Wall fell, an urban planner in London got a phone callfrom a colleague in Moscow saying, basically, "Hi, this is Vladimir. I'd like to know, who's in charge of London's bread supply?"

And the urban planner in London goes, "What do you mean, who's in charge of London's —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 -- I haven't really thought of it. It basically organizes itself."

It organizes itself. That's an example of a complex social system which has the ability of self-organizing, 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 the incentives. You don't plan the details, and people will figure out what to do, how to adapt to this new framework.

And let's now look at how we can use this insight to combat road congestion.

This is a map of Stockholm, my hometown. Now, Stockholm is a medium-sized city, roughly two million people, but Stockholm also has lots of water and lots of water means lots of bridges -- narrow bridges, old bridges -- which means lots of road congestion. And these red dots show the most congested parts, which are the bridges that lead into the inner city. And then someone came up with the idea that, apart from good public transport,apart from spending money on roads, let's try to charge drivers one or two euros at these bottlenecks.

Now, one or two euros, that isn't really a lot of money, I mean compared to parking charges and running costs, etc., 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've still got 80 percent left of the problem, right? Because you still have 80 percent of the traffic. Now, that's also wrong, because traffic happens to be a nonlinear phenomenon, meaning that once you reach above a certain capacity thresholdthen congestion starts to increase really, 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 Stockholmon January 3, 2006, and the first picture here is a picture of Stockholm, one of the typical streets, January 2. 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 have sort of gotten used to charges. Wrong again. It's now six and a half years ago since the congestion charges were introduced in Stockholm, and we basically have the same low traffic levels still.

But you see, there's an interesting gap here in the time series in 2007. Well, the thing is that, the congestion charges, they were introduced first as a trial, so they were introducedin January and then abolished again at the end of July, followed by a referendum, and then they were reintroduced again in 2007, which of course was a wonderful scientific opportunity. I mean, this was a really fun experiment to start with, and we actually got to do it twice. And personally, I would like to do this every once a year or so, but they won't let me do that. But it was fun anyway.

So, we followed up. What happened? This is the last day with the congestion charges, July 31, and you see the same street but now it's summer, and 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 so extremely quickly. The first day they all came back. And this effect hanged on. So 2007 figures looked like this.

Now these traffic figures are really exciting and a little bit surprising and very useful to know,but I would say that the most surprising slide here I'm going to show you today is not this one. It's this one. This shows public support for congestion pricing of Stockholm, and you see that when congestion pricing were introduced in 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 charges were there is not what you would expect, that people hated it more and more. No, on the contrary, they changed, up to a point where we now have 70 percent support for keeping the charges, meaning that -- I mean, let me repeat that: 70 percent of the population in Stockholm want to keep a price for something that used to be free.

Okay. So why can 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 can understand this, then maybe we can figure out how people can be so happy with this. Well, so we did this huge interview survey with lots of travel services, and tried to figure out who changed, and where did they go? And it turned out that they don't know themselves. (Laughter) For some reason, the car drivers are -- they are confident they actually drive the same way that they used to do. And why is that? It's because that 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, and each dayall 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, who changed their mind? Who changed their opinion, and why? So we did another interview survey, tried to figure out why people changed their mind, and what type of group changed their minds? And after analyzing the answers, it turned out that more than half of them believe that they haven't changed their minds. They're actually confident that they have liked congestion pricing all along. Which means that we are now in a positionwhere we have reduced traffic across this toll cordon with 20 percent, and reduced congestion by enormous numbers, and people aren't even aware that they have changed,and they honestly believe that they have liked this all along.

This is the power of nudges when trying to solve complex social problems, and 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. (Applause)