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

568,810 views ・ 2020-05-28

TED-Ed


请双击下面的英文字幕来播放视频。

翻译人员: Lipeng Chen 校对人员: Joyce He
00:06
You’re cruising down the highway when all of a sudden
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你正在高速公路上开着车,突然间,
00:09
endless rows of brake lights appear ahead.
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前方出现了无数排刹车灯。
00:12
There’s no accident, no stoplight,
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没有事故,也没有红灯,
00:14
no change in speed limit or narrowing of the road.
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限速没有变化,路也没有变窄。
00:17
So why the @#$%! is there so much traffic?
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那么,为什么路突然变得这么堵?
00:21
When traffic comes to a near standstill for no apparent reason,
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当交通没有缘由的停滞时,
00:24
it’s called a phantom traffic jam.
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这种现象被称为“幽灵堵车”。
00:27
A phantom traffic jam is an emergent phenomenon
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幽灵堵车是一种突发现象,
00:30
whose behavior takes on a life of its own, greater than the sum of its parts.
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很难加以控制, 且整体状况比各部分之和还糟糕。
00:35
But in spite of this, we can actually model these jams,
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但尽管如此,我们事实上可以 对这类拥堵建立模型,
00:38
even understand the principles that shape them—
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甚至理解它们形成的原理——
00:41
and we’re closer than you might think
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想要在将来避免此类交通拥堵,
00:43
to preventing this kind of traffic in the future.
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事实上,我们其实已经比你 想象的还要更进一步了。
00:46
For a phantom traffic jam to form, there must be a lot of cars on the road.
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幽灵拥堵的形成需要 路上有很多辆车。
00:51
That doesn’t mean there are necessarily too many cars
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这不一定意味着车太多了
00:54
to pass through a stretch of roadway smoothly,
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以至于无法顺利通过某一路段,
00:56
at least not if every driver maintains the same consistent speed and spacing
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至少当每个司机都与其他司机保持 一致的速度和间距时,
01:01
from other drivers.
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幽灵堵车就不会发生。
01:02
In this dense, but flowing, traffic,
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在这密集但流动着的车流中,
01:04
it only takes a minor disturbance to set off the chain of events
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只要有细微的变动 就会造成连锁反应,
01:09
that causes a traffic jam.
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导致堵车。
01:11
Say one driver brakes slightly.
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比如一个司机稍稍踩了刹车。
01:14
Each successive driver then brakes a little more strongly,
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后面的每一个司机就会 踩刹车踩得更重,
01:18
creating a wave of brake lights that propagates backward
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致使路上的车辆形成
01:21
through the cars on the road.
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一条向后延伸的刹车灯浪。
01:23
These stop-and-go waves can travel along a highway for miles.
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这种停停走走的情况 可以在高速公路上绵延数英里。
01:28
With a low density of cars on the road,
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当路上车流密度较低时,
01:31
traffic flows smoothly because small disturbances,
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交通会很顺畅,因为小的干扰,
01:34
like individual cars changing lanes or slowing down at a curve,
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比如个别车辆变道或弯道减速,
01:38
are absorbed by other drivers’ adjustments.
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可以被其他司机的调整所抵消。
01:41
But once the number of cars on the road exceeds a critical density,
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但是一旦路上车辆的数量 超过临界密度时——
01:45
generally when cars are spaced less than 35 meters apart,
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一般来说指车距小于 35 米——
01:50
the system’s behavior changes dramatically.
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整个系统的行为 就会发生巨大变化。
01:53
It begins to display dynamic instability, meaning small disturbances are amplified.
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首先会出现动态不稳定性, 也就是说小的干扰会被放大。
01:59
Dynamic instability isn’t unique to phantom traffic jams—
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动态不稳定性并不是 幽灵堵车所特有的——
02:03
it’s also responsible for raindrops, sand dunes, cloud patterns, and more.
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它也存在于雨滴、沙丘、 云朵形态等等。
02:10
The instability is a positive feedback loop.
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这种不稳定性是种正反馈回路。
02:13
Above the critical density,
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在临界密度之上时,
02:15
any additional vehicle reduces the number of cars per second
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任何额外的车辆都会降低 每秒通过路上某一点
02:19
passing through a given point on the road.
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汽车的数量。
02:22
This in turn means it takes longer for a local pileup
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这反过来意味着需要更长的时间 才能让局部的一队车辆
02:26
to move out of a section of the road, increasing vehicle density even more,
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通过某段道路, 更进一步增加了车流密度,
02:31
which eventually adds up to stop-and-go traffic.
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最终导致了停停走走的交通。
02:35
Drivers tend not to realize they need to break far in advance of a traffic jam,
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司机往往意识不到他们要 远在堵车之前就刹车,
02:40
which means they end up having to brake harder to avoid a collision.
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这意味着他们最后要狠狠的刹车 来避免撞车。
02:44
This strengthens the wave of braking from vehicle to vehicle.
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这加强了车与车之间刹车的传递。
02:48
What’s more, drivers tend to accelerate too rapidly out of a slowdown,
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更糟糕的是,司机在减速后 往往会加速过快,
02:53
meaning they try to drive faster
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也就是说他们会比
02:55
than the average flow of traffic downstream of them.
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后方的平均车流开得更快。
02:58
Then, they have to brake again, eventually producing another feedback loop
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然后,他们必须再次刹车, 最终形成另一个反馈回路,
03:02
that causes more stop-and-go traffic.
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造成更多停停走走的拥堵。
03:05
In both cases, drivers make traffic worse
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在这两种情况中,司机让 堵车变得更糟糕了
03:09
simply because they don’t have a good sense of the conditions ahead of them.
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仅仅因为他们不能很好地 预知前方的车况。
03:13
Self driving cars equipped with data on traffic conditions ahead
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自动驾驶汽车配有前方路况的数据,
03:18
from connected vehicles or roadway sensors
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这些数据来自于 互联的车辆或路况传感器,
03:21
might be able to counteract phantom traffic in real-time.
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可能可以实时避免幽灵堵车。
03:24
These vehicles would maintain a uniform speed, safety permitting,
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在保证安全的情况下 这些车辆会保持一致的速度,
03:29
that matches the average speed of the overall flow,
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和整体车流的平均速度匹配,
03:32
preventing traffic waves from forming.
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进而避免拥堵车潮的形成。
03:35
In situations where there’s already a traffic wave,
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在已经存在拥堵车潮的情况下,
03:38
the automated vehicle would be able to anticipate it,
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自动驾驶汽车可以进行预测,
03:41
braking sooner and more gradually than a human driver
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相比人类司机更早 并且更缓慢地刹车,
03:44
and reducing the strength of the wave.
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从而降低拥堵车潮的强度。
03:47
And it wouldn’t take that many self-driving cars—
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这并不需要很多辆 自动驾驶汽车就能实现——
03:51
In a recent experiment, one autonomous vehicle for every 20 human drivers
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在最近的一次实验中,每 20 名人类司机 对应一辆自动驾驶汽车,
03:56
was enough to dampen and prevent traffic waves.
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就足以缓解并预防拥堵车潮形成。
04:00
Traffic jams are not only a daily annoyance–
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堵车不仅仅是日常的烦恼,
04:03
they’re a major cause of fatalities,
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还是意外死亡、资源浪费
04:05
wasted resources, and planet-threatening pollution.
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和地球污染的主要原因。
04:09
But new technology may help reduce these patterns,
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但是新型技术 可以帮助减缓这些状况,
04:12
rendering our roads safer,
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让我们的道路更加安全、
04:14
our daily commutes more efficient, and our air cleaner.
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日常通勤更加有效、 空气更加清洁。
04:18
And the next time you’re stuck in traffic,
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下次你再遇到堵车时,
04:20
it may help to remember that other drivers aren’t necessarily driving spitefully,
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这样想想也许会有帮助: 其他司机并不一定是存心这样的,
04:24
but are simply unaware of road conditions ahead— and drive accordingly.
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他们只是无法预测前方的路况, 并相应地调整驾驶策略。
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