What city introduced the traffic light in august 1914?

Cleveland

London England.

A LARGE CITY CAN HAVE AS MANY AS 10,000 INTERSECTIONS. MULTIPLY THIS TIMES ROUGHLY EIGHT AND IT IS CONCIEVABLE THAT A CITY SUCH AS LOS ANGELES OR HOUSTON COULD HAVE 80 THOUSAND TRAFFIC SIGNALS...

18th century.

Both are commonly used. However, if you want to emphasize the ownership of the lights, use " city's ".