Every language and every country has it's own slang. There are even huge differences between each US State. South Africa is no different—it has dozens of words used to describe people, places and things that other English-speaking nations do not have.
Some of these include poppie (a ditzy woman), snackwich (a grilled cheese sandwich), and tekkies/tackies (sneakers). Somewhat confusingly, they call traffic lights "robots." They of course call actual robots "robots" too.
The practice of calling traffic lights robots came about when they were first installed in South Africa. Then, they were called "robot policemen" and the name was shortened over time.