How The Traffic Light Became The Emergency Light

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modern emergency light -

We have all been there in our lives. You’re driving home from work tired from a long day from work. Then you see in the mirror behind you the ominous flashing lights of a police car. You pull over to the side but the car comes in behind you. Then you finally stop while the flashing lights illuminate your vehicle and much of the rest of the neighborhood.

While you wait for the officer to check your identity, perhaps you notice a nearby traffic light switching through its lights at the end of the street.

But how are these lights related?

Before automotive traffic became a daily hassle, there were rail hazards. The first recorded locomotives first emerged five centuries ago in Austria. These machines were at first human powered. Later they developed steam power and finally diesel propulsion.

All of these trains were dangerous at track intersections.

Rail supervisors have long used “semaphores” poles at intersections to display “stop” and “go” signals to train drivers.

When horse drawn carriages began congesting the London streets in 1860, the railway passenger John Peake Knight suggested refashioning the poles for horse traffic.

This led to the world’s first traffic light opening at the intersection of George Street and Great George Street in Westminster, London on December 9th, 1868. The first light was a green and red gas fired lamp. It was operated by a police officer and about as safe as you’d expect. A month later it exploded in the officer’s face severely injuring him and the light was removed.

Then in 1910, the American inventor Ernest Sirrine introduced the first automatic traffic signal in Chicago. This signal recycled the display of locomotives with a “stop” and “proceed” sign.

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first automatic traffic light -US Patent Office

Two years later the Police Officer Lester Farnsworth Wire invented the first electric light in Salt Lake City, Utah. This light resembled a four sided birdhouse and sat in the middle of the intersection. It required a Police Officer to operate it.

Next came James Hoge of Cleveland, Ohio. In 1914, he invented the first electric signal that could automatically switch between “stop” and “move”.

Next came the classic signal with red and green lights in 1917. William Ghiglieri of San Francisco invented this signal.

At about the same time Police cars were dealing with the same problem of recognition. The early vehicles had very limited electric power. This led to the first Police cars using an extra tail light on the front fender, front bumper, or the hood in the 1930s. The red lights would read “Stop” or “Pull Over”.

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Vintage Fire Light - ebay

Then in 1948, the Federal Signal company produced the first red “gumball” and later blue light. These lights worked by rotating a mirror around a fixed bulb, spinning the bulb, or simply flashing.

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Gumball light - Elvis Santana of freeimages

In 1935 the Germans chose to equip their vehicles with cobalt blue lights as a blackout measure in the years ahead of World War 2. The Germans choose blue light since the light is easily scattered by the atmosphere and this makes it more difficult for bombers to see the vehicles at altitude.

Blue lights additionally have the edge of being more visible to the colorblind. They could have been chosen over and above to stand out against the red taillights of heavy traffic. Another possibility is that blue lights are more visible at night.

Over the next thirty years police vehicles integrated the single “gumball” lights into their display or they used “gumball” lights in combinations on a bar.

By the end of the 1960’s the “gumball” lights had merged into the single “light bar” that is the standard of emergency vehicles today.

Modern police “light bars” use arrays of LEDs to broadcast light in all directions and cost at least a thousand dollars. Organizations can choose from red, blue, amber, green, and white lights with customizations available. The “light bars” can also be programmed to flash in as many as thirty lighting configurations.

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Modern lightbar - Federal Signal AeroDynic light

Nearly all emergency automobiles in the United States use forward facing red lights.

Amber or yellow lights are common for utility trucks.

White lights are optional and are many times only used in combination with other colors. White lights are generally only used as flood lights.

Green lights are used to illuminate security light bars for Homeland Security and private security.

Blue lights are exclusively for the use of law enforcement, fire fighters, and emergency medical transports.

Some states designate purple for the Coroner’s.

Customer Engineer with a passion for AI Development and writing featured stories

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