It blew up. Believe it or not, the first traffic light was put up long before there were cars.
The first traffic signal was installed in 1868 in London, England, on a corner outside the British Houses of Parliament. It had a set of arms that were used during the day. These arms were small versions of the ones used today at railroad crossings.
At night, when people couldn’t see the arms, the signal used red and green gas lanterns to control traffic. The purpose of the signal was to get people safely across the street, which was crowded with horse-drawn carriages and wagons. After a short period, the traffic light blew up and killed a nearby policeman.
The type of traffic signals we know today did not come about until 1914, when the first one was put to use in Cleveland, Ohio.