Traffic control

This weblog post was the oldest draft still waiting to be published. It was originally written on 2018-04-04, being initially saved at 17:21. It was finally scheduled to be published eight years and 39 minutes later, 2026-04-04 at 18:00. If you are reading this, there was no last minute reprieve. It was finally published!

Traffic lights/signals/robots, often = stoplights, are signalling devices positioned at road intersections, pedestrian crossings, and other locations in order to control the flow of traffic. Traffic refers to the movement of people, vehicles, ships, aircraft and more, in an area, along a street, through an air corridor, over a water route.

For those wanting to be impressed with my ability to use Google translate, here are some translations of traffic light into assorted languages: 紅綠燈 (Chinese), trafiklys (Danish), liikennevalo (Finnish), feux de circulation (French & Quebecois), Ampel (German), umferðarljós (Icelandic), trafikklys (Norwegian), trafikljus (Swedish), Світлофор (Ukrainian).

Traffic lights usually consist of three signals, transmitting meaningful information to road users through colours and graphic representatios, arrows especially, but also stick figures, sometimes lettering. The usual traffic light colours are: red to stop traffic, amber for traffic change, and green to allow traffic to proceed. These are arranged vertically or horizontally in that order, by international standard. Despite this, there are variations in traffic light sequences and laws.

There is a need in traffic situations for all participants to have a common understanding of what is happening. With various levels of autonomous as well as driver driven vehicles operating on streets, it is important that everyone (and everything, in an age of autonomous vehicles) be aware of what is to happening, especially at intersections. Situation awareness, and sometimes just clarity are the terms I prefer to use to describe a situation where people have this common understanding.

The world’s very first traffic signal was invented by John Peake Knight (1828-1886), a railway engineer from Nottingham. With 1102 fatalities and 1334 injuries documented on London roads in 1866, the signal was installed in London in 1868. It was based on railway signals mounted on a pillar, with three semaphore arms, and red and green gas lamps for nighttime use, and was operated by a police constable. It was an instant success until it was destroyed just over three weeks later by a gas explosion. The signal was declared a public safety hazard and removed.

I am not impressed with traffic in London. I remember a London taxi driver complaining to me, perhaps forty years ago, after I completed crossing a street, that he had no obligation to stop or slow down for me, if I was not in a zebra crossing (which did not exist at this intersection). Only his compassion had resulted in my continuing to live. I think this was the moment I decided that Britain, with its class society, lacked the social norms I appreciate.

Traffic lights, as we know them today, were invented in 1912 by Lester Wire (1887-1958), in Salt Lake City. He was inspired by a Biblical text from Matthew 5:15, Neither do men light a candle, and put it under a bushel, but on a candlestick; and it giveth light unto all.

James Hoge (1866 – 1926) received a patent in 1913 for a manually controlled red and green (no amber) traffic light, installed in 1914 in Cleveland, Ohio. Its operational rhythm could be adjusted in an emergency.

In 1917, Italian born, San Francisco resident William Ghiglieri (1866 – 1946) received a patent for an automatic traffic signal using red and green lights, with a provision for manual operation.

In 1920, William Potts (1883-1947) of Detroit invented electrically powered, hanging, automatic traffic lights to control four-way intersections. These were the first to include amber “caution” lights. They were first installed in Detroit.

In 1923, Garrett Augustus Morgan Sr. (1877-1963) received a patent for a reliable and inexpensive manually operated signal. Shortly after he sold his rights to General Electric for $40 000. GE used the patent in a failed attempt to gain a traffic light monopoly.

Yet again in Detroit, the first traffic tower in the US was installed at the intersection of Woodward and Michigan Avenues, in 1917. As they began being used in other cities, the towers assumed a wide variety of shapes and sizes, but were generally big, tall, right in the middle of all the traffic action, and visible. These traffic controlling structures were often manned, but not necessarily so, and were available with or without traffic lights.

Laying claim to the world’s oldest operating traffic light is the city of Ashville, Ohio. The light in question controlled traffic from its installation at the corner of Main and Long Streets for about 50 years, starting in 1932. Designed by Ashville resident Teddy Boor (1878 – 1954), the signal featured a slowly rotating hand that swept across the face of each light to let drivers know how much time remained before a light change. The signal was removed in 1982 by the Ohio Department of Transportation, which ordered it to be replaced with a standard traffic light.

While it is no longer controlling car traffic, the light is still operating, and directing foot traffic inside the Ashville Museum, where it is the most popular exhibit. According to officials, “there is plenty of foot traffic.” The light has also been featured on Oprah and An American Moment With James Earl Jones

The first automated pedestrian signs featuring a lighted “don’t walk” signal were installed in New York City on 1952-02-05. The problem with these is that they assume an understanding of the written English language. Depictions of people walking or standing do not require an understanding of a specific language.

Red has been used to mean stop. The shade of red used in most traffic signals contains yellow hues to improve its visibility for people with color blindness. Opposite red on a color wheel is green, used for go. This colour was also used on on railways because white light could be misinterpreted, especially during daylight hours. Traffic light green  includes some blue for colorblind people. Yellow, or amber, is the most visible color in the spectrum, and can be seen from a greater distance.

Traffic lights are designed to be seen in bright daylight. When they are equipped with Fresnel lenses they can focus light on a specific viewing area and obscure it from others.

Russian designer Evgeny Arinin (? – ) believes traffic signals could communicate instructions more clearly. He has designed a LED alternative, using shapes, including arrows and icons. The design concept shows some of the challenges of current traffic signage systems. A traffic signal rarely operates independently. It is part of a larger, sometimes scattered, ecosystem of signs that alert drivers to things like roadwork, school crossings, unprotected lefts, and when they can and can’t turn right on red. Drivers have to synthesize all this information as they approach an intersection. Soon enough, so will autonomous vehicles.

Most adults have a representation of a traffic light in their mind. That does not mean that people have a uniform conception of its operation. So there is a need to ensure that there is a consensus in people’s minds regarding their interaction with these object. Just take a common situation where one meets with an amber signal. Some people will want to accelerate through the intersection, while others will want to stop immediately. This can lead to actions that result in crashes, especially if the accelerating vehicle is behind the stopping vehicle.

One of my favourite traffic lights is the East German Ampelmännchen, designed by Traffic psychologist Karl Peglau (1927–2009) as part of a 1961 proposal for a new pedestrian traffic lights layout. In German, die Ampel (Plural, Ampeln) refers to a traffic light. So these are traffic light men.

In addition, he made vehicular traffic signals, shown below, where Peglau’s proposal for a traffic lights layout (on the left) is compared to modern traffic lights (on the right). Peglau criticised the fact that the standard traffic lights colours = red, yellow, green, did not provide for road users who were unable to differentiate between colours (ten percent of the total population).

This traffic was designed by Municipal Signal, Ville St-Laurent, Montreal, Quebec, Canada. They also designed and constructed the first Solid State Traffic Controller, presented at the 1965 Miami, Florida meeting of the International Municipal Association. In those ancient times, solid state referred to electronic devices, such as transistors or crystals, that could control current = amperage, without the use of moving parts, heated filaments, or vacuum gaps.

My own work with traffic control occurred taking a microprocessor course. One major exercise was to design an intersection with four signals, each with three lights. We then had to modify it to fit changing parameters. Initial modifications included duration changes. Later, more advanced changes were needed, such as allowing approaching emergency vehicles to have right-of-way.