• Yellow means "caution" because it's almost as easy to see as red
黄色代表“注意”,因为它几乎和红色一样显眼。
From the earliest days of motoring up until the mid-1900s, not all stop signs were red --many were yellow, along with yield signs, because at night it was all but impossible to see a red stop sign in a poorly lit area. The yellow stop-sign craze began in Detroit in 1915, a city that five years later installed its first electric traffic signal, which happened to include the very first amber traffic light, at the corner of Michigan and Woodward Aves.
从最早开始出现汽车到20世纪中期,并不是所有的停车信号都用红色——很多使用黄色,让路标志也是,因为夜晚在光线极暗的地方根本看不见红色的停车信号。“黄色停车信号潮”始于1915年的底特律,五年后,这座城市在密歇根和伍德沃德大街安装了第一个首次包括黄色灯的电子交通信号灯。
But what of those weird yellow stop signs, you ask? As materials and technologies evolved, the ability to produce highly reflective signs meant that red could resume its natural spot in the sign hierarchy, leaving the still-highly-visible yellow (it's second only to red in terms of visible wavelength) to the domain of "caution." That's why school zones and buses, crosswalks, and other important warnings are yellow today.
你是不是想问,那些奇怪的黄色停止标志又是干什么的呢?材料学和高技术的发展使得人们研发出高度反光指示灯,因此红色才能在信号灯中重拾“停车霸权”,将可视度较高的黄色(可视波长仅次于红色)留在了“警告”的位置。这也是为什么学校区、公交站、人行横道和其它重要位置使用黄色警告信号灯的原因。
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