The humble traffic light has provided us with a simple method of traffic control for over 150 years. Through the use of colour-coded aspects, it has cut queues at junctions, made narrow bridges easier to cross over or under, and has provided road workers with an alternative to standing with a big lollipop!
History
It's Victorian London... well, 1868 to be exact, and London’s busiest junction is getting worse by the day. Increasing numbers of people are moving around Westminster, in horse-driven vehicles and on bicycles. Parliament, in sight of the junction – where George Street would meet Bridge Street – was getting increasingly annoyed with the congestion and delays. Something needed to be done.
Consideration was made to deploying a
police officer to marshal traffic at the junction, however it
was deemed to be too large for one officer to control on his
own. Some form of device was needed to help, and that help was
to be inspired by the booming railway system.
John P Knight's semaphore traffic signal in "stop" (left) and "proceed with
caution" positions.
In order to operate the signal, the on-duty police officer would rotate a handle at the foot of the pole, which would raise or lower the arms, and allow the gas fire to pass behind the coloured lenses.
On 2 January 1869, less than a month after their first use a faulty gas pipe resulted in one of the signals exploding. The on-duty policeman suffered severe burns, and the project was immediately cancelled.
Despite this major setback, this wasn't the end of the story.
Three decades later, in 1912, Lester Wire, a Salt Lake City police officer, came up with a new system of traffic signals. Instead of using gas lanterns, he devised a signal that used electric red and green lights.
However, Wire's design was never introduced. It would take a second person to do this - James Hoge, who made two small changes to the signal: the words "STOP" and "MOVE" on the lenses, and a buzzer to alert when the signals were to change. In 1914, the new design was finally installed at an intersection in Cleveland, Ohio.
Despite the success of the design, William Potts, from Detroit, noted that the design had one major flaw - the signals were still manually operated. In 1920, he designed the world's first automatic traffic signal; not only that, he also introduced a three-light system, and also the over-hanging four way signal.
Despite this, it would be another seven years before the UK benefited from these new signals. Princess Square in Wolverhampton was chosen as the guinea pig, and in 1927 our first set of automated traffic lights were installed.
Originally, signal heads were made out of metal, gaining the nickname "tin lantern" as a result. Various manufacturers developed their own versions, including Plessey and Forest City, but generally keeping to the same design.
However, by 1965, the Ministry for Transport decided that a new design of signal was needed to replace the now rather old-fashioned design. They appointed David Mellor, a designer who had also developed stainless steel cutlery, to create a new design.
Yet, instead of using steel or other metals, the new design would be constructed from polypropylene. Lighter, cheaper but still very strong! Halogen bulbs were used for the lights, ideal as they would be bright yet long-lasting.
The first Mellor signals were installed in 1973, and soon sprung up across the country. Like the previous "tin lanterns", these new signals would be made by a number of manufacturers, but the required design standards meant that all such signals would look exactly the same.
Despite this, in recent years, design standards have changed as each manufacturer has developed their own styles. Increasingly common are modular units, where each coloured lens is on its own individual block.
Another change is the development of LED signals, which are becoming ever more popular due to the benefits of being low maintenance and significantly longer-lasting than the traditional halogen bulbs.
Signal types
Below is a guide to the most common varieties of traffic signal lanterns found in the UK.
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