The Stops And Starts Of Designing Traffic Lights

You might not realise it when you've been trapped behind the same red light for five minutes, but traffic lights, when they're timed and tuned correctly, are actually pretty good at making traffic move. Really.

Traffic lights, believe it or not, organise fast-moving cars into groups based on the time of day and road usage, smoothly sending them through intersections that might otherwise net (a lot more) headaches and insurance claims.

But it took a flood of cars — the half million in 1910 that skyrocketed to nine million 10 years later — to make us realise that traffic, especially where roads meet, can be a dangerous problem. It wasn't just cars competing for the right of way — horses and bicycles were also vying for a place on the road. At the time, crossroads were mediated by hand waving, an attending officer or a game of chicken.

City-dwellers were the first to seek a solution. An early traffic signal model made in Chicago in 1910 had the words, "Stop" and "Proceed" visible to drivers. The instructions didn't do much for evening travellers, though, as the sign had no lights.

Another model popped up in Salt Lake City two years later, designed by someone who knew the importance of an effective signal: a police officer. Lester Wire invented the first traffic light that actually lit up. His device, made in 1912, was basically a box with two circles carved in the front. A red light and a green light placed in the openings told vehicles whether to stop or go.

But a stoplight invention wasn't patented until the early 1920s, when Garrett Morgan, an inventor in Cleveland, Ohio, witnessed a terrible collision between a car and a horse-drawn carriage that left a girl seriously injured.

Morgan realised that one of the problems with current signals was that the transition from go to stop and back again was too abrupt. The signs, he thought, should instead have an in-between indicator that warned people to slow down before the traffic flow changed directions.

His design, which was operated manually and shaped like a cross, incorporated "a visible indicator which is useful in stopping traffic in all directions before the signal to proceed in any one direction is given," according to his 1923 patent. An attendant operated a crank to fold the arms of the cross upwards. When the top and side pieces were all lined up vertically, the device displayed the illuminated word "Stop". An alarm bell option attached on top like a hat to further punctuate the four-way stop. When the intersection was cleared, the attendant swivelled the signal, and the word "Go" faced the oncoming traffic.

Now for the sad part of the story. Morgan sold the patent to General Electric for $US40,000. (OK, maybe it doesn't sound that sad, since that's more than half a million dollars in today's money.) But the reason he sold the patent, rather than developing the stoplight himself and becoming richer than Jesus Christ's rich uncle is because he was an African American. And this was not his first life-saving invention! Some years earlier, he and a group of volunteers used a gas mask he designed to save workers trapped in a tunnel being dug under Lake Erie that had collapsed. When news got out of his heroic actions and the gadget that made the rescue possible, orders flooded in. But when buyers discovered that Morgan was African American, nearly all the orders were cancelled. Fearing he would experience similar problems with his traffic light, he sold his idea. Horrible.

Automatic lights soon replaced the manual set up, but Morgan's three-action system was clearly the precursor to the traffic signals we rely on today. He invented other indispensable stuff throughout his life, too, creating the first chemical hair straightener and a self-extinguishing cigarette filter. Just before his death in 1963, the US government honoured Morgan with an award for his groundbreaking work in road safety.

Image: Flickr/vizzzual.com


Comments

    imagine being able to claim royalties for every traffic light erected?!? ...wow!

    " a self-extinguishing cigarette filter"

    Definitely a big life saving technology there as any firefighter would tell you.

    The problem with traffic lights is that they are typically reactionary which is inefficient. In some places there are a series of linked lights to improve peak traffic flow but they do not take into consideration current conditions so when travelling in heavy traffic in wet conditions you are unlikely to make the other lights in the series. Sensors are generally right before the lights instead of further back down the street to anticipate traffic flows. Also there are still an alarming number of crashes as intersections with traffic lights.

    The other thing I have also observed is that traffic can quite often flow more freely during power blackouts that when the lights are in operation so whether this is just a temporary effect of drivers being more cautious or points towards lights in some cases not being warranted is up for discussion.

    I think the next step will be some sort of "transponder" based system. Ever parked at an intersection waiting for nothing or had to slow down for a light that turns green by the time you've stopped.
    Rather than relying on road sensors, traffic light systems should work by taking into account traffic flow at different times of the day, collecting data from approaching and waiting vehicles, to offer a similar level of traffic "fluidity" as a roundabout.

    Traffic Lights have been synchronised in many parts of the world for over 20 years (I first came across it as a teenager, in 1992, and I'm sure it was in use for a while then)..... So if you are in a part of the world with merely reactionary lights I am sorry... BUt of course the Lights still aren't nearly as intelligent as they could be...

    In this day of wireless information ,why not file a driving plan (like a flight plan) for commuting to work, then the lights will be able to use the transponder in your car to identify you and everyone else who travels the same way every day, and make the lights work better to get you there without stopping all the time.... If we could drive at 30km/hr and not stop, it would be faster and use less fuel than the current rush and stop peak hour traffic... 0-60, then stop, 0-60 then stop... Ok in the middle of the day and night, it is easy to travel quickly, as the lights are green more often on main roads....

    Thanks to the guy who invented traffic lights.... At least it means that we usually only have tail end accidents nowdays, not so many head-ons. (Except for the D**kheads who always run the solid red, their day always comes, but sadly they sometimes take out some innocent)

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