A traffic light is designed to provide three pieces of information: Red, yellow and green. But a subset of impatient drivers want more information. Thus we do the trick of memorizing the amount of milliseconds that will transpire between perpendicular traffic's new red light and our forthcoming green light. Or at intersections with side-shrouded lights, twitchy drivers can watch for the flashing Don't Walks to subside, then time their gas-stomp accordingly.

Interestingly, in the early days of traffic lights there was a design alternative to the one we all know that would have obviated the scenario described above. In 1936 Australian engineer Charles Marshal developed this clock-like design, whereby a sweeping hand indicated stop-and-go status and allowed the end user to see the progression:

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In this video showing a restored Marshalite and the Melbourne Museum Victoria, you can see the pace of the hand:

Around the same time, and apparently independently, German inventor Josef Heuer designed something similar. His Heuerampel ("Heuer traffic light") was also rotary-based, though it featured no yellow section and a rather strange quadrant design, which I find harder to read than if the circle were merely bisected.

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Both the Marshalite and the Heuerampel were locally implemented. The Marshalite served some Australian roads beginning in the 1940s, while Heuer's design saw service starting in the 1930s in Germany, Austria and the Netherlands.

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By the 1960s Australia decommissioned the Marshalites, and Europe pulled the last Heuerampel down in 1972.

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They were axed not because their UX was deemed inferior, but because of their technological underpinnings: The signals could not be quickly reprogrammed, as modern-day signals could, to deal with changing traffic conditions.