在很多年里，纽约市政部门逐步停用了该市控制人行横道信号灯的大部分按钮，但一直没怎么声张。他们认定，计算机操控的计时器更好用。到了2004年，3250个按钮中只剩

Red means "stop," green means "go," and yellow means "hurry up and make that damn light." Why those colors, though? Why not blue, purple, and brown? I have to admit that aside from a hunch that it had to do with wavelengths,

Most of us are used to seeing traffic lights above eye level. Whether we are driving, biking, or walking, traffic signal