The invention of the turn signal involved multiple contributors over time:
- In 1907, Percy Douglas-Hamilton patented a device using illuminated hands on each side of the car to signal turns. His idea simplified communication of turning with lights that resembled hand signals already in use.
- In 1914, silent-film actress Florence Lawrence designed a mechanical arm that moved a flag on the rear bumper of the car to indicate turning direction and stopping. Although she never patented her invention, it is considered an early and important step towards modern turn signals.
- A patent for a modern-style flashing turn signal was granted to Edgar A. Walz Jr. in 1925, which was the first of its kind to resemble the turn signals used today, but it did not gain commercial success immediately.
- Oscar J. Simler patented a turn signal device in 1929 that also integrated brake and stop signals.
- Buick was the first U.S. car manufacturer to offer electric flashing turn signals as an optional feature in 1939, expanding to front and rear lights by 1940.
In summary, Percy Douglas-Hamilton originated an early electric turn signal patent in 1907, Florence Lawrence pioneered a mechanical signaling arm in 1914 without patent, and Edgar A. Walz Jr. developed the first modern flashing turn signal patent in 1925. The commercial introduction and popular adoption of turn signals began with Buick's 1939 models.