How Green Was My Signal
Like Ken Todd and the thieves in The Italian Job remake, I have my troubles with traffic signals. But I’m always interested in the evolution of a standard technology and the various roads not taken along the way. That’s why I was delighted by this entry, via boingboing gadgets, from Charles Marshall, an Australian engineer from the 1930s.
Rather than binary lights, the signal ticks away the phases like a colorful clock or analog scale (you can see quite clearly how one direction gets more “green time” than the other). Visually, it conjures in me feelings of everything from Kandinsky to RAF Spitfires to The Hudsucker Proxy. As historian Gordon Sessions notes in his no-nonsense titled survey Traffic Devices: Historical Aspects Thereof (ITE, 1971), this sort of thing was once rather common, one of the many rival entrants for traffic control schemes jockeying for supremacy in the world’s streets. Early on, for example, there was often no “amber phase,” just green and red; in early 20th century Cleveland, Sessions notes, “at the time of the change from red to green or vice versa, a bell was sounded to warn traffic of the impending change.” Los Angeles, meanwhile, had its own version of the Marshall device, at the corner of Wilshire and Western. As described by Sessions, there was “a clock-like circular face with an indicator hand which revolved, showing the motorist the amount of ‘stop’ and ‘go’ interval that remained.”
“Countdown signals” are becoming quite common for pedestrians (and many drivers use these to “time” the lights to their advantage), but the idea of showing drivers remaining signal time is today rare — though I did come across this in Delhi, where drivers use the time indicator to decide whether to shut off their engines at the lights and save fuel. This is an obvious benefit, but as with most things in traffic, there are trade-offs: Drivers may pay more attention to trying to judge how much time is left than the actual traffic ahead, or people still in the intersection; or they may use their knowledge of the remaining phase to accelerate to unsafe speeds. Still, the Marshall device is a tantalizing alternative to the aesthetic monotony of standardized traffic signals.
This entry was posted on Wednesday, June 4th, 2008 at 7:18 am and is filed under Traffic Engineering, Traffic History, Traffic Signs, 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.