Hey grandma drivers, this is big rig sciencepappy Trace for DNews, what's your 20? Old cars

嗨，各位阿嬤級駕駛。我是big rig sciencepappy在Trace for DNews的報導，還記得你20歲時?

and highways often have a speed limit of 55 because of efficiency. It all started in 1973,

老車和公路因為效率問題，通常被速限在55英里。其實這項規定源自1973年

when the U.S. was under an oil embargo. To conserve resources, Congress tied the state

當時美國處於石油禁運規定下，國會為了保護天然資源，規定各州

speed limits to federal highway funding; basically forcing states to adhere to 55 or else they'd

速限，並挹注罰款所得到聯邦公路基金，藉此強迫各州將基本速限訂在55，否則州政府

lose millions in highway money. They picked 55 because the Argonne National Laboratory

會被扣公路基金。而他們挑55英里係因美國阿岡國家實驗室

found that was the speed most cars would get the best miles-per-gallon. Once the embargo

發現它是大部分車輛可以獲得最佳油耗的速度，而禁運結束

ended, Congress was reluctant to lift the limit, until 1995. Afterward, States went

一直到 1995年，國會才被迫提高速限。後來，各州

on a tizzy trying to pick new speed limits. Most chose 70, but some use 65 or 80 (yes,

各州瘋狂挑選新的速限。大部分州選擇70，但有一些採用65或80

Texas, I know, you got a lilttle bit of 85)！ But how did they decide on

（是的，德州到 80）我知道，你可能都小小加速到 85，但他們究竟如何

those numbers?

決定出這個數字？

Well, firstly, exceeding the speed limit or driving too fast for the conditions is the

嗯，首先，超過速限或是飆速過快常是

primary cause of auto crashes globally. Which is why we have speed limits in the first place.

全世界汽車肇事的主因。這就是為什麼我們必須將速限擺在首位的原因。

But it's important to know "too fast for conditions" is a big deal. Because speed limits are determined

但要知道「太快條件」是一個大問題，而且非常重要。由於車輛的速限

by data, but the data is from three main things: nature, engineering, and humans!

由三大資料來決定，包括自然因素、道路工程和人為因素等！

For example: when highway and traffic researchers decide a speed limit they take into account

例如：在決定速限時，公路工程和交通運量研究人員必須考慮

weather, visibility, terrain, location and so on -- nature. They also take into account

氣候、能見度、地形和地段等自然因素。同時也需計入

the purpose of the road, crash risks, traffic and truck flow monitors (those two rubber

道路設計目標、撞擊、運量和卡車流量監控（兩條

tubes you sometimes run over on the road), what the road is made of, the amount of shoulder

你在馬路上會開車壓過的軟管）等構成道路的要素，以及與路面相鄰的

next to the road, maintenance schedules -- that's engineering. And of course how humans actually

路肩寬度和維修日程--這些均屬工程因素。當然還有人們究竟如何

USE the road which we'll come back to in a sec. They then take that data and use different

使用道路的因素（我們馬上回來），他們採用這些數據並使用不同的

computer and cost-based models to specifically pick the speed for that stretch of road! The

電腦和以成本為基礎的數值模型，挑出最適合該路段的速度！

human component has to do with safety, but ALSO our ability to actually DRIVE on that

人因部分則牽涉安全，當然也包括個人實際開車上路

road at that speed. The operating speed model is often used, sort of crowd-sources the speed

的速度，因此實際操作速度常受採用，它有點像「群眾外包」的

limit using something called the "85th percentile rule."

速限，使用所謂的「第85百分位數規則」

Basically, researchers observe the average speed people naturally want to use on a stretch

基本上，研究人員會觀察駕駛人在一段直路上自然使用的平均速度

of road, and lob off the speediest 15 percent! Research has shown, that the 85th percentile

然後剔除最快的15%！研究顯示， 85百分位數

is a speed most people would be comfortable driving. Which is super important, because

的速度也是讓最多駕駛開起來最暢快的速度，而究竟

be it 55 or 85 the researchers and lawmakers want a speed limit that is "accepted as reasonable

55或 85英里是研究人員或立法委員想要的，其實是最多用路人

by a majority of road users." So, nature, engineering and humans together factor into

合理可接受的速限。因此很自然地，工程和人為兩項均加入

our speed limits.

我們的速限內。

And that all kind of makes sense. Faster speeds tend toward stretches of road in Montana or

這些都很合理。全美國最高的速限在蒙大拿或德州

Texas, where roads are open, sparsely populated and straight, while dense, high-traffic, urban

有些路段是開放的，人煙稀少且筆直，至於密集、高流量、位在市區

areas with more weather considerations tend toward slower speeds. Duh, right?

以及有天候考量者，則會有較低的速度限制，對吧?

Speed limits are human things, but they're based on physics plus biology. Faster speeds

速限其實是很人為的，但它們均植基於物理加上生物。速度越快

means less time for our animal brains to react when something goes wrong. According to the

意謂著我們動物本能的腦袋，在事情出錯時反應時間越短

European Road Safety Observatory: for every 1 km/h increase in speed there's a 3 percent

按照歐洲道路觀察報告指出，時速每提高一公里，就增加 3%

increase in crashes.It's an old joke that it's not the crash that kills you, but the

撞車機率。有個老笑話說，撞車不會害死你，因為

sudden stop at the end. The faster you are going, the data says, the more kinetic energy

車子到最後都會停下來。而資料顯示，你的速度越快，在車內的連結動能

is in the vehicle, and the worse the crash is going to be. This is why some regions likely

越大，車禍也就越慘。這也是為何有些地區會視天候、路況和駕駛人而

have lower speed limits for their conditions, roads and drivers.

降低他們的速限

Once the speeds are picked, researchers are constantly going back and adding new data

一旦速限選定，研究者會持續回去並加進新資料

and testing the road at various speeds, and in various conditions. Look, everyone who

以不同速度和不同條件測試道路。注意，每個駕駛

drives a car wants to get where they're going as efficiently, quickly, and safely as possible,

開車都希望能以最有效率、最快和最安全的方式抵達目的地

even traffic researchers! Every road, and every type of road is different! The reason

即便是交通研究者亦然！每一條、每一類的道路均各有差異！這也是

that speed limit is on THAT road, is a mix of lots of data, and lots of human effort.

擺在路上的「速限」是一大堆資料和一票人努力的綜合規定。

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Sponsor Read 也盡了努力讓你的

car clean. Techron by Chevron’s patented Precision Clean Technology targets and removes

保持乾淨，由 Chevron取得的專利精準清除科技則對準

deposits left by lower tier gasolines. It bonds with and breaks apart carbon deposits,

並可去除較低級別的汽油所留下的沉積物，並比其他添加劑技術，

more effectively than other additive technologies. Techron gets into the deepest parts of the

更有效連結然後打破積碳。Techron 深入引擎內部

engine, where the most destructive deposits built up, and sweeps them away.

即最具破壞性積碳的沈積處，加以掃除

But what about self-driving cars? Should they have speed limits too? Are they even safer?

至於自駕車呢?該有速限嗎？它會更安全嗎?

Trace looks int-- wait a minute, I'm TRACE! It's a good video, check it out. :D

Trace正在調查，等一下，我就是Trace，來看我們精心製作的好短片

What do you think? Should speed limits be higher? Lower? Are you just waiting for the

你認為呢? 該提高還是降低速限呢？還是你已在期待

self-driving revolution? Tell me about it!

自駕駛革命? 告訴我們吧！