Why the @#$% is there so much traffic? - Benjamin Seibold

譯者: Judy Huang 審譯者: Pui-Ching Siu

You’re cruising down the highway when all of a sudden

你正在高速公路上開車，

突然間，

endless rows of brake lights appear ahead.

前方出現了數不盡的煞車燈。

There’s no accident, no stoplight,

沒有發生事故，沒有紅燈，

no change in speed limit or narrowing of the road.

限速沒有變化， 道路寬度也沒有變窄。

So why the @#$%! is there so much traffic?

但為什麼會塞車呢？

When traffic comes to a near standstill for no apparent reason,

當交通沒有明顯的理由 而停滯的時候，

it’s called a phantom traffic jam.

這現象就叫做「幽靈堵車」。

A phantom traffic jam is an emergent phenomenon

幽靈堵車是一種新崛起的現象，

whose behavior takes on a life of its own, greater than the sum of its parts.

它的變化難以控制， 大於其各個部分的總和。

But in spite of this, we can actually model these jams,

但是，我們其實可以 模擬這些交通堵塞，

even understand the principles that shape them—

甚至了解造成它們的原因——

and we’re closer than you might think

將來的這種交通堵塞

to preventing this kind of traffic in the future.

會比你想像中更容易避免
。

For a phantom traffic jam to form, there must be a lot of cars on the road.

要形成幽靈堵車， 路上必須有很多輛車。

That doesn’t mean there are necessarily too many cars

這並不代表有太多輛車，

to pass through a stretch of roadway smoothly,

導致無法順利通過一段道路，

at least not if every driver maintains the same consistent speed and spacing

至少每個司機都保持 一致的速度和間距的話，

from other drivers.

幽靈堵車就不會發生。

In this dense, but flowing, traffic,

在這密集但流動的交通中，

it only takes a minor disturbance to set off the chain of events

只要有輕微的變動， 就會造成連鎖反應，

that causes a traffic jam.

導致塞車。

Say one driver brakes slightly.

若一名司機稍微踩了煞車一下，

Each successive driver then brakes a little more strongly,

後面的司機都會踩稍微大力一點。

creating a wave of brake lights that propagates backward

導致路上的車輛形成

一波向後延伸的剎車燈波浪。

through the cars on the road.

These stop-and-go waves can travel along a highway for miles.

這種走走停停的波浪 可以在高速公路上持續好幾英里。

With a low density of cars on the road,

路上的車流密度較低時，交通順暢，

traffic flows smoothly because small disturbances,

如果發生很小的變化，

like individual cars changing lanes or slowing down at a curve,

比如某輛車在換車道或在彎道減速，

are absorbed by other drivers’ adjustments.

其他的司機能夠調整解決。

But once the number of cars on the road exceeds a critical density,

一旦路上車輛的數量超越臨界密度，

generally when cars are spaced less than 35 meters apart,

一般而言，當車距小於 35 公尺時，

the system’s behavior changes dramatically.

整個系統的行為就會產生巨大變化，

It begins to display dynamic instability, meaning small disturbances are amplified.

開始呈現動態不穩定， 就是小的變化會被放大。

Dynamic instability isn’t unique to phantom traffic jams—

動態不穩定並非幽靈堵車所獨有，

it’s also responsible for raindrops, sand dunes, cloud patterns, and more.

雨滴、沙丘、雲朵形狀等等也有。

The instability is a positive feedback loop.

這種不穩度性是正面反饋環。

Above the critical density,

超過臨界密度，任何多出的車輛

any additional vehicle reduces the number of cars per second

都會造成每秒通過 路上某一點的汽車數減少，

passing through a given point on the road.

This in turn means it takes longer for a local pileup

以致區段的塞車 得要花更多時間來清除，

to move out of a section of the road, increasing vehicle density even more,

使得車流密度更為增加，

which eventually adds up to stop-and-go traffic.

累積成時行時止的狀況。

Drivers tend not to realize they need to break far in advance of a traffic jam,

司機往往沒意識到他們要 遠在堵車之前就煞車。

which means they end up having to brake harder to avoid a collision.

指的是說他們經常透過 緊急煞車来避免撞車。

This strengthens the wave of braking from vehicle to vehicle.

這會強化車輛間剎車的浪潮。

What’s more, drivers tend to accelerate too rapidly out of a slowdown,

更驚人的是，司機們在減速後 往往都會加速過快，

meaning they try to drive faster

也就是說他們的車速會比

than the average flow of traffic downstream of them.

下游的平均車流還快。

Then, they have to brake again, eventually producing another feedback loop

他們需要再次煞車， 最後再形成一個反饋循環，

that causes more stop-and-go traffic.

造成更多時行時止的狀況。

In both cases, drivers make traffic worse

在這兩種情況中， 司機讓交通變得更糟糕，

simply because they don’t have a good sense of the conditions ahead of them.

僅僅因為他們無法預知前方的路況。

Self driving cars equipped with data on traffic conditions ahead

自動駕駛汽車都具備著

從互聯汽車或路段感應器 蒐集到的前方路況數據，

from connected vehicles or roadway sensors

might be able to counteract phantom traffic in real-time.

它們也許可以即時避免幽靈堵車。

These vehicles would maintain a uniform speed, safety permitting,

這些車輛會在安全情況下 保持固定速度，

that matches the average speed of the overall flow,

配合總流量的平均速度

preventing traffic waves from forming.

來預防交通波浪再次形成。

In situations where there’s already a traffic wave,

在波浪已經形成的情況下，

the automated vehicle would be able to anticipate it,

自動駕駛汽車能夠更早發現，

braking sooner and more gradually than a human driver

它會比人們開車時更早逐漸地煞車，

and reducing the strength of the wave.

足以成功地抵掉波浪的強度。

And it wouldn’t take that many self-driving cars—

其實並不需要那麼多 自動駕駛汽車——

In a recent experiment, one autonomous vehicle for every 20 human drivers

在最近的一項實驗中，

如果每 20 位司機中 有一輛自動駕駛汽車，

was enough to dampen and prevent traffic waves.

就足以抵銷和防止交通波浪。

Traffic jams are not only a daily annoyance–

塞車不只是日常的煩惱，

they’re a major cause of fatalities,

它們是導致死亡、浪費資源

wasted resources, and planet-threatening pollution.

和造成地球污染的主要原因。

But new technology may help reduce these patterns,

但是新技術或可幫助減少這些模式，

rendering our roads safer,

讓我們的道路更安全、

our daily commutes more efficient, and our air cleaner.

日常通勤更有效率、空氣更好。

And the next time you’re stuck in traffic,

下次您遇到交通堵塞時，

it may help to remember that other drivers aren’t necessarily driving spitefully,

請記住其他的司機 並不是存有惡意地開車，

but are simply unaware of road conditions ahead— and drive accordingly.

他們只是不知道該如何因應 前方的狀況來開車。