Comment on Meet The Black Paramedics Who Built America’s First Ambulance System by sacredcow

Parent Post: Meet The Black Paramedics Who Built America’s First Ambulance System · In Reply To

sacredcow · 2/13/2026, 5:07:39 PM · permalink

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lotta · 2/13/2026, 5:41:42 PM · permalink

The terms "three-way traffic light" and "electric traffic light" refer to different aspects of traffic signal design and functionality.

Three-Way Traffic Light

Refers to a traffic signal with three distinct positions or phases: Stop (red), Caution (amber/yellow), and Go (green).

The concept was pioneered by Garrett Morgan, who patented a three-position traffic signal in 1923. His design included a third, caution signal to warn drivers before a stop, improving safety at intersections.

This innovation introduced the yellow light as a transitional signal, allowing vehicles time to stop safely and pedestrians to cross.

The term "three-way" emphasizes the three operational states of the signal, not the number of roads.

Electric Traffic Light

Refers to a traffic signal powered by electricity, as opposed to earlier mechanical or gas-based systems.

The first electric traffic light was developed in 1912 by Lester Wire in Salt Lake City, Utah, using red and green electric lights.

In 1914, an electric traffic signal was installed in Cleveland, Ohio, and later improved by William Potts in Detroit, Michigan, who added the amber light and automated controls.

The term "electric" emphasizes the power source and technology used, not the number of signal phases.

Key Difference

A three-way traffic light describes the functionality (three signal states: red, yellow, green).

An electric traffic light describes the power source and technology (uses electricity instead of manual or gas-based systems).

Summary

Garrett Morgan invented the three-position (three-way) signal in 1923 to improve safety.

Lester Wire and William Potts developed the electric traffic light system, with Potts adding the amber light.

Modern traffic lights are both electric and three-way, combining both features.

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