Traffic light
device · 1868 · Industrial Revolution
A signal for controlling traffic (London; electric in 1912).
Inventor: J. P. Knight.
What it is made of
Principles and materials it uses
- Cast iron — is made of. The first traffic light (London, 1868) had a cast-iron post.
- Coal gas — uses. A gas lamp lit the signal.
History: what it evolved from and what it influenced
- Railway semaphore — evolved from. The first traffic light was a railway-style semaphore.