Choose the best answer:
The first traffic signal was invented by a railway signaling engineer. It was installed (33) ___ the Houses of Parliament in 1868. It (34)_____ like any railway signal of the time, and was operated by gas. (35) ____, it exploded and killed a policeman, and the accident discouraged further development until cars became common. (36) ____ traffic lights are an American invention. Red – green systems were installed in Cleveland in 1914. Three - color signals, operated (37) _____ hanz d from a tower in the (38) _____ of the street, were installed in New York in 1918. The first lights of this type to (39) ____ in Britain were in London, on the junction between St. James‘s Street and Piccadilly, in 1925. Automatic signals were installed (40) ____ year later. In the past, traffic lights were special. In New York, some lights had a statue on top. In Los Angeles the lights did not just change silently, but would ring bells to (41) _____ the sleeping motorists of the 1930s. These are gone and have been (42) ____ by standard models which are universally adopted.

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