2. You Are Causing the Traffic Jams You Hate

Traffic jams have long been chalked up to the sheer volume of traffic on the roads,¹⁰but it turns out that even heavy traffic can flow smoothly if people maintain a constant speed. The problem is that we can’t. Researchers at the University of Exeter have found that just one person even slightly stepping on their brakes can have a devastating effect on the traffic around them.¹¹

On even moderately busy roads, it can take only a few minutes for traffic to grind to a complete halt behind someone who tapped their brakes to let another driver merge.¹²The standstill¹³usually occurs several minutes after the braking, well after the person that caused the problem in the first place has gone on his or her way.

3. Horse Manure¹⁴

While the problems of modern traffic might be new, the transportation methods of the olden¹⁵days had their share of issues. Anyone who thinks that traffic pollution is a modern invention should look at the problems that befell¹⁶London at the turn of the century. In the late 1800s, almost all traffic was horse-drawn, resulting in 11,000 horse-drawn carriages and several thousand 12-horse buses making their way across the London streets every day.

All of those horses produced manure—about 7-15 kilograms (15-35 lb¹⁷) of it per day, to be exact. In 1894, it was estimated that it would have only taken 50 years for the manure to cover all of London’s streets almost 3 meters (9 ft¹⁸) deep. Other major cities, like New York, had similar problems. New York City’s horses produced an average of 1 million kilograms (2.5 million lb) of manure each day, requiring the city to spend a lot of money cleaning it up.

Something had to be done about it, and the result was the first international urban planning conference ever held. When no solution was reached, the landscape was looking bleak¹⁹. Fortunately, it wasn’t long before the advent²⁰of the car solved the problem. It arguably brought an entirely new set of problems with it, but things could have been different if the electric cars of Victorian London had been more economical.

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10. chalk up: 取決于；sheer: 完全的。

11. University of Exeter: 埃克塞特大學，英國一所著名綜合性大學，在2013/14QS世界大學排名榜上位居英國第26位，世界第168位；devastating: 極大的。

12. 即使在交通不是很擁擠的路面上，一旦有人剎車讓其他司機并道，幾分鐘之內，交通就會徹底堵住。moderately: 適度地；grind to a halt: 慢慢停止。

13. standstill: 停止。

14. manure: 糞便。

15. olden: 古老的，往昔的。

16. befell: （befall的過去時）發(fā)生。

17. lb: =pound，磅。

18. ft: =feet，英尺。

19. bleak: 荒涼的。

20. advent: 出現，到來。