You can freely build on How Garrett Morgan Invented the Three-Position Traffic Signal
This patent expired in 1942. Every claim — 0 independent, 0 dependent — is now unenforceable. Anyone can use, reproduce, manufacture, sell, or offer for sale this technology without a license.
Original assignee
Individual
Patent granted
1923
Expired
1942
Forward citations
2
What this patent covers
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 is now free to use
All 0 claims of US 1475024 are in the public domain. Specifically:
The 0 dependent claims add narrowing limitations and are also free.
What is NOT covered
Patent expiry frees this specific invention. Separately-patented improvements made after expiry may still be protected.
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.
Who is building on this today
Modern traffic management companies like Econolite and Siemens build on the logic of intersection safety intervals, though they now use advanced AI and sensor-based systems instead of mechanical poles.
Products built on expired version of this technology
Early 20th-century manual traffic control towers
Mechanical semaphore-style intersection signals
How to cite this patent in your documentation
Individual. US Patent 1475024. Traffic signal. Granted 1923, expired 1942. Now in the public domain.
Note: This is a convenience citation. Consult a patent attorney for formal freedom-to-operate analysis.
PatentBrief is an educational resource and does not provide legal advice. Patent expiration information is derived from USPTO records and may not reflect continuation patents, divisional filings, or separately-patented improvements. For commercial use or production decisions, obtain a formal freedom-to-operate (FTO) opinion from a registered patent attorney.