The History and Origin of Traffic Lights: A Complete Guide

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Nanjing Gaoqiao Traffic Technology Co., Ltd

NJGQ has 17 years history in traffic light design and making since 2006, we also have partnered with Siemens (China) since 2016.Our focus and advantages are: traffic light & traffic light controller, whether it is normal power or solar power, portable or mobile, normal or solar warning traffic light, all kinds of traffic signal board, as well as light poles

The History and Origin of Traffic Lights: A Complete Guide

date:2026-03-09 09:33:01

The History and Origin of Traffic Lights: A Complete Guide

The History and Origin of Traffic Lights
Traffic lights are one of the most common inventions controlling vehicle and pedestrian flow worldwide. The fascinating history of traffic signals spans over a century.

When Were Traffic Lights Invented?
The first traffic signal was invented in 1868 in London, England. It was manually operated by a police officer to control horse-drawn carriage traffic on Bridge Street near the Houses of Parliament.
John Peake Knight, a railway signal engineer, created this device using semaphore arms raised or lowered to indicate “stop” or “caution,” with red and green gas lamps at night. Unfortunately, it exploded just 23 days after installation, injuring its operator.

The Evolution of Traffic Lights
1914: First Electric Traffic Light
The first electric traffic light was installed in Cleveland, Ohio, USA. It featured red and green lights changed every 30 seconds by a police officer.
1920: The Three-Light System
Detroit police officer William Potts invented the first three-light signal by adding the amber (yellow) light between red and green. This became the global standard.
Modern Era: Smart Traffic Lights
Today’s traffic lights use:
• LED technology for energy efficiency
• Smart sensors that detect traffic volume
• AI-powered systems that optimize traffic flow

Who Invented the Traffic Light?
• John Peake Knight (1868) – First traffic signal
• William Potts (1920) – Added the amber light
• John Harris (1924) – First four-way three-color signal

Why Red, Yellow, and Green?
• Red: Inherited from railways, means “stop”
• Yellow: Warning color before signal changes to red
• Green: Means “go,” easily distinguishable from red

Impact on Road Safety
Traffic lights have reduced serious accidents by up to 70% at intersections, organizing traffic flow and minimizing collision risks.
 
Keywords: traffic lights history, origin of traffic lights, who invented traffic lights, traffic signal evolution

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