* This week marks the centenary of the installation in Cleveland, Ohio of the world's first electrically-powered traffic light system.
Situated on US Route 20 at the junction of Euclid Avenue, it featured four pairs of red and green lights (marked 'STOP' and 'MOVE') situated on each corner. They were wired up to a control booth in which a policeman dutifully sat, making watchful decisions about when to flick the switch. A loud buzzer indicated when the lights were about to change.
* It wasn't the first traffic light, however. London holds that honour, although it's a slightly dubious one. Installed in Westminster in December 1868, it was a part-semaphore, part-gaslight affair that exploded within the first month of use, injuring the policeman operating it. It was quietly dismantled, and London didn't see traffic lights again until electric ones were installed on Piccadilly in 1926.
* The lights used in Cleveland were designed and patented by one James Hoge, but other names are associated with their development. Lester Wire, a policeman working Salt Lake City, had patented a device in 1912 that looked like a birdhouse on a pole, while in 1920 William Potts had the bright idea of the amber light to replace that buzzer.
Garrett Morgan, inventor of the gas mask, also patented a hand-cranked mechanical system that revolved and rotated, but it was red, amber and green that would show the way forward.
* When traffic lights were first installed in the town of Canajoharie, New York, the local paper ran an article which set out in detail what each coloured light meant. Men were advised to cut out the article from the paper and glue it to the inside of their hat in case they forgot. Today, red for stop and green for go is a more instinctive thing. At least, it is for most people.