The Origin and Evolution of Traffic Lights


The Origin and Evolution of Traffic Lights

Especially when running late, we often see these tri-coloured poles on intersections as the bane of our existence. However, the frustration borne from a few minutes of inconvenient delay is quickly forgotten when faced with the anarchy of a dysfunctioning traffic light.

Playing the role of road coordinators, traffic lights are imperative to control the flow of traffic on the road; creating a sense of order and crucial in preventing collisions.

Let’s have a closer look at how traffic lights came about and how they’ve evolved through time.

1868, London: The first traffic signal

The first ever traffic signals were installed outside the Houses of Parliament in London, in December of 1868 — 40 years before the first car was commercially available. Adapted from railroad signal systems, J. P. Knight, a British railway engineer proposed the model to control the traffic of horse carriages, allowing pedestrians to cross the roads safely.

Image via Wikipedia

Image via Wikipedia

These gas-fueled lights were manually controlled by a police officer using semaphore arms. During the day, the semaphore arms were raised or lowered to signal vehicles to proceed or stop. At night, instead of arms, gas-lit lights were employed. Red signalled carriages to stop, as the colour was commonly represented as danger or caution. Green signalled stop, as it was culturally an emotionally reassuring colour and corresponded with safety.

This system worked well, but the life of the first traffic signals was ultimately short-lived. Barely a month in, a gas leak caused one of the lights to explode, severely injuring a police officer, and the gas-lit traffic lights were deemed unsafe for use, and was stopped immediately.

London would not see another traffic light until 1929.

Early 20th century, the U.S. : Police officers and traffic towers

In the United States, traffic signalling was done by policemen. Towers had been built in the early 1900s to allow officers a better vantage point of traffic. The police officers would either use red and green lights, or wave their arms to indicate stop or go.

The need for a better traffic system was increasingly apparent as cities became more crowded with the growth of industrialization and rapidly increasing traffic.

1912, Salt Lake City: Bulbs in a birdhouse

By now, traffic police here had already had several near misses while manually directing traffic in the middle of Salt Lake City intersections, so officers were moved to the side of the road in the early 1900s.

Lester F. Wire, the head of the traffic division at the Salt Lake City Police Department, built a wooden box resembling a birdhouse and installed two bulbs on each side — one bulb dipped in green paint, and the other dipped in red paint. The box sat on a ten-foot pole in the middle of the intersection and, once connected to overhead trolley wires, enabled officers from the side to manually flip a switch to direct traffic.

Images by Utah Department of Transportation

Images by Utah Department of Transportation

However, Lester Wire’s birdhouse-style traffic light was not patented, leaving the claim to his invention being the first traffic light often disputed.

1914, Cleveland: The first electric system

Meanwhile, more than 4000 people had died from car crashes in the United States in 1913, the same year Ford Model T’s started gaining widespread use. The roads weren’t ready for vehicles that could speed at 65kmh, and crowded intersections often met with collisions, with police officers at the center of these dangerous crossroads.

A Cleveland engineer, James Hoge, borrowed the red and green signals used by railroads and tapped into the electricity that ran through its trolley lines. His system consisted of 4 pairs of red and green lights on a 4-way intersection with the words ‘STOP’ and ‘MOVE’ mounted on intersection corner poles, wired to a central control booth which was operated by a policeman.

Image by the US Patent Office via Vox

Image by the US Patent Office via Vox

Image by The American City and County

Image by The American City and County

Hoge’s lights made its debut in 1914 on Euclid Avenue, 105th Street, 4 years before its patent was issued. Drivers approaching the intersection now saw two lights suspended above it. A policeman sitting in a booth on the sidewalk controlled the signals with a flip of a switch.

1920, Detroit: First tri-coloured, 4-way lights

The next and most enduring evolution of traffic lights was introduced in Detroit, also known as Motor City, and the city Ford Motor Company was founded in. Ford made cars accessible to the masses, and very soon, STOP and MOVE were insufficient to control the volume of street traffic.

William Potts, a policeman in Detroit invented the first tri-coloured lights, introducing a third colour — amber (or yellow) to indicate motorists to slow down. The introduction of the cautionary amber light helped minimise accidents caused by running red lights.

Image via reddit by CrotchWolf

Image via reddit by CrotchWolf

Detroit became the first city to implement the four-way, three-coloured lights, designed to be suspended over the centre of a junction. Soon after, other cities such as New York and Philadelphia began introducing lights with linked circuits, allowing several intersections to change at the same time.

1922, Houston: Automatic timers introduced

Traffic towers started being controlled by automatic timers in 1922, paving the way for automation instead of manually operated lights. Its main advantage was that it saved money by replacing traffic officers. The city of New York was able to reassign 5,500 of its 6000 traffic officers, saving the city $12.5 million.

1923, Cleveland: The three-position traffic light is patented

Image via Wikipedia

Image via Wikipedia

Meanwhile, back in Cleveland, an inventor named Garrett Morgan, after witnessing an accident, patented an affordable traffic signal using a similar tri-coloured system. The design was inexpensive and allowed the installation of a lot more lights. This attracted the attention of General Electric; Morgan sold the patent for $40,000, and GE went on to monopolise the manufacturing of traffic signals in the United States.

1950s: Computerised traffic lights

With the invention of computers in the 1950s, computerised detection enabled quicker changing of lights. A pressure plate was placed at intersections, so once a car was on the plate, computers would detect that a car was waiting at the red light. As computers evolved, its detection became more sophisticated, making it possible to change the length of a green light based on the volume of waiting cars.

1990s: Countdown timers

A relatively modern evolution, timers are especially useful for pedestrians as a gauge for how much time they would have to cross an intersection, and for drivers to know how the amount of time before the light switches.

Almost two decades into the 21st century, we are looking towards a future with driverless cars, with smart cars practicing the art of nonverbal communication in autonomous intersections, just like drivers once did a century ago. Perhaps the new sign of modernity would be a city with no need for a traffic light.