Traffic lights. Ah, the humble traffic light, something something awards-show pablum about traffic lights or some kind of crap. Let's just get to it.
The traffic light was first introduced in London on December 10, 1868. The reason for its invention came down to, well, traffic. There was getting to be a lot of it in London, and they weren't waiting for the car to be invented to clog up the streets. Carriage drivers were having trouble yielding to each other, and to help them out, a man named John Peake Knight invented a device to regulate things.
It was not electric-powered, though. That wouldn't come until a light in Cleveland in 1914. This one was manually operated by a police officer on site, who would manipulate a movable arm in the manner of semaphore signals to denote what a carriage should do. If the arm was down, that meant go. If it was at a 45-degree angle, it meant caution. If it was horizontal, it meant stop. At night, gaslit lamps would be lit to serve as a further aid. Red still meant stop, but originally, green meant caution.
The light was put at Bridge Street and Great George Street, near the Houses of Parliament. That'd be right about here. All it was really supposed to do was help the members of Parliament cross the street. In that task, for the first couple weeks, it worked out well enough.
And then on the following January 2, the traffic light exploded. A gas leak caused one of the lanterns to blow up, with the traffic cop obligingly underneath. The cop at the least got his face burned half off, and at the worst died (the records aren't completely clear on that). The traffic light came down real quick after that, and its replacement wouldn't be built until 1929.
By then, they were fairly sure lightbulbs wouldn't randomly explode.