# How Garrett Morgan Invented the Three-Position Traffic Signal

> Garrett Morgan's 1923 patent for a T-shaped traffic signal introduced a 'caution' position to manage vehicle flow more safely at busy intersections.

- **Patent:** US 1475024
- **Original title:** Traffic signal
- **Owner:** Individual
- **Granted:** 1923
- **Status:** Public domain (expired)
- **Times cited:** 2
- **Field:** automotive, mechanical

## What it does

The patent describes a T-shaped pole featuring three distinct positions to control traffic flow. Unlike earlier two-position signals that only signaled 'stop' or 'go', this design introduced a third state to halt traffic from all directions simultaneously. This allowed for a safer transition period, preventing collisions between vehicles clearing the intersection and those just starting to move.

## What it does NOT cover

- Does not cover electric or automated traffic light systems.
- Does not cover signals that use colored lights (red, yellow, green) as the primary indicator.
- Does not cover systems that detect vehicle presence via sensors or loops.

## The clever bit

The innovation was the introduction of a 'neutral' or 'caution' state that stopped all traffic flow, rather than just switching between two opposing directions.

## Real-world examples

1. Early 20th-century manual traffic control towers
2. Mechanical semaphore-style intersection signals

## Why it matters

Before this invention, intersections were dangerous places with primitive, two-state signals that often led to accidents. Morgan's inclusion of a 'stop-all' position provided the necessary buffer time for city streets, forming the conceptual foundation for the modern yellow light interval used worldwide today.

## Frequently asked questions

### What does How Garrett Morgan Invented the Three-Position Traffic Signal cover?

Garrett Morgan's 1923 patent for a T-shaped traffic signal introduced a 'caution' position to manage vehicle flow more safely at busy intersections.

### Who owns patent US 1475024?

Individual owns this patent, granted in 1923.

### When does this patent expire?

This patent has expired and is now in the public domain — anyone can use the invention freely.

### What is patent US 1475024 cited by?

This patent has been cited by 2 later patents that build on its ideas.

### What problem does this patent solve?

Before this invention, intersections were dangerous places with primitive, two-state signals that often led to accidents. Morgan's inclusion of a 'stop-all' position provided the necessary buffer time for city streets, forming the conceptual foundation for the modern yellow light interval used worldwide today.

### What does this patent NOT cover?

Does not cover electric or automated traffic light systems.

**Full plain-English explainer:** https://patentbrief.org/patent/us/1475024/traffic-signal-morgan

**Original patent:** https://patents.google.com/patent/US1475024

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_Source: PatentBrief — https://patentbrief.org. Patent facts are from public records; the plain-English explanation is PatentBrief's._


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