Red Yellow Green
In Traffic I make a passing mention of the evolution of traffic light sequences:
Others wanted the yellow light shown before the signal was changing to red and before it was changing from red back to green (which one sees today in Denmark, among other places, but nowhere in North America).
Reader Claire writes in to note that she remembers this sequence being used in the U.S.:
I distinctly remember passing through signals of this type on arterial streets in Chicago between 1977 – 1983. They were mostly located west of the L tracks on arterial streets like Belmont, Armitage, Fullerton, Devon, and Ashland.
Now, I didn’t say they were never used in the U.S., just that they aren’t anymore — although I may be wrong here and I’d be curious to see an example. She helpfully points us to Willis Lamm’s Traffic Signal page, which contains video examples of these “really funky signal phases.”
I’ve seen international studies on the potential problems with the red-amber-green phase, but haven’t really heard or read an account of why these phases vanished in the U.S. (though I’m sure the information is out there, in some back issue of the ITE Journal). I can imagine there are pedestrian issues, not to mention intersection clearance issues. And given that hardly anyone drives a manual shift in the U.S., one of the perceived virtues of that system is now largely lost here, like an old piece of slang no one uses anymore.
This entry was posted on Tuesday, July 14th, 2009 at 12:01 pm and is filed under Traffic Engineering, Traffic Gadgets, Traffic Signals, Traffic Wonkery. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.