{"id":12229,"date":"2026-02-02T00:21:09","date_gmt":"2026-02-02T05:21:09","guid":{"rendered":"https:\/\/www.trafficsafetystore.com\/blog\/?p=12229"},"modified":"2026-02-10T14:22:32","modified_gmt":"2026-02-10T19:22:32","slug":"who-invented-the-yellow-light","status":"publish","type":"post","link":"https:\/\/www.trafficsafetystore.com\/blog\/who-invented-the-yellow-light\/","title":{"rendered":"Who Invented The Yellow Light?"},"content":{"rendered":"\r\n\r\n\r\n
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Who Invented the Yellow Traffic Light?<\/h1>\r\n

The yellow (amber) light is one of the simplest safety upgrades ever added to the roadway\u2014and it\u2019s saved countless fender-benders (and worse) by giving drivers a clear\r\n\u201cheads up\u201d before red. So who invented it? The short answer: a Detroit police officer named William Potts<\/strong>, who introduced the amber caution phase and helped standardize the\r\nthree-color traffic signal<\/strong> we still use today.<\/p>\r\n\r\n<\/header>\r\n\r\n

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Before Yellow: Early Signals Were Basically \u201cStop\u201d or \u201cGo\u201d<\/h2>\r\n

Early traffic control relied heavily on officers directing movement by hand\u2014or on simple two-color signals that flipped between red and green.\r\nThe problem was scale: as vehicle speeds increased and intersections grew busier, an abrupt change from \u201cgo\u201d to \u201cstop\u201d didn\u2019t give drivers enough\r\ntime to react safely. That gap is exactly where the yellow light comes in.<\/p>\r\n\r\n

William Potts and the Birth of the Yellow \u201cCaution\u201d Phase<\/h2>\r\n

Histories of U.S. traffic signals commonly credit William Potts<\/strong>\u2014a Detroit police officer and traffic-signal superintendent\u2014with inserting a\r\nyellow (amber) caution light<\/strong> between green and red to warn drivers of an impending stop.\r\nAccording to the\r\nLibrary of Congress<\/a>,\r\nPotts introduced the yellow light concept around 1917<\/strong> and later developed a major advancement:\r\na four-direction, three-color electric traffic signal<\/strong> by 1920<\/strong>.<\/p>\r\n

Transportation museums and historical collections support the reasoning behind the design.\r\nEarly illuminated signals used only red and green; adding an amber \u201ccaution\u201d phase gave drivers time to slow safely\r\nand helped the three-color system become the U.S. standard by the mid-1930s.<\/p>\r\n

One widely cited early tri-color, four-direction signal is associated with Detroit.\r\nAn artifact record from the\r\nHenry Ford Museum<\/a>\r\ndocuments a Potts-era signal design linked to early installations at major Detroit intersections,\r\nincluding Woodward Avenue & Fort Street<\/strong>.<\/p>\r\n\r\n

What About Garrett Morgan? (An Important Part of the Story)<\/h2>\r\n

You may also see Garrett A. Morgan<\/strong> credited in traffic-signal history\u2014and for good reason.\r\nIn 1923<\/strong>, Morgan patented a three-position traffic-control device<\/strong> designed to improve intersection safety\r\nby introducing a controlled transition phase, including an all-direction stop.\r\nAccording to the\r\nFederal Highway Administration<\/a>,\r\nMorgan\u2019s invention influenced later traffic-control systems, even though it differed mechanically from the electric red\u2013yellow\u2013green signals that became standard.<\/p>\r\n

In short: Potts<\/strong> is widely credited with introducing the yellow light into the modern electric three-color sequence<\/strong>,\r\nwhile Morgan<\/strong> is recognized for advancing safer intersection control through a patented three-position signal concept.<\/p>\r\n\r\n

Why the Yellow Light Matters for Safety<\/h2>\r\n

The yellow phase functions as a built-in reaction buffer. It helps reduce:<\/p>\r\n\r\n