Garrett Morgan patented his three-position T-shaped traffic signal in 1923.
Morgan’s design was a manually operated signal with moving arms, rather than the fully automatic electric traffic lights commonly seen today. It presented Stop and Go indications and could be placed in an intermediate position to warn traffic to proceed cautiously. The T-shaped arrangement helped control traffic approaching an intersection.
Morgan developed the idea after seeing the danger created by collisions between motor vehicles and horse-drawn vehicles. His patent, U.S. Patent No. 1,475,024, was granted on November 20, 1923. He later sold the rights to General Electric, reportedly for $40,000.
A frequent misconception is that Morgan invented the first traffic light or the modern three-colour automatic signal. Other inventors had already developed important electrical and amber-light systems. Morgan’s achievement was a patented, practical three-position design that added an all-stop or caution stage to intersection control.