world's first traffic signal

The world’s first traffic signal popped up in London in 1868, outside the Houses of Parliament, because even Victorians got tired of horse‑drawn chaos.

Designed by railway engineer J. P. Knight, it used semaphore arms by day and a gas‑lit red/green lamp by night—ingenious until the gas system exploded in early 1869 and injured the poor constable operating it.

It was promptly scrapped, and the idea napped for a few decades.

The first successful electric traffic lights arrived in Cleveland, Ohio, in 1914, and the modern red‑amber‑green setup spread not long after.