Nine of the so-called sex boxes, able to accommodate one car at a time, are located in the city's Sihlqai district, where residents have complained at length about on-street prostitution, The Independent of Britain reported.
Each garage-sized box has alarm buttons and a security guard presence. Customers drive in, choose one of the prostitutes at work there, negotiate a price, then park in a box.
"Prostitution is a business. We cannot prohibit it, so we want to control it in favor of the sex workers and the population," said Michael Herzig, a Zurich social services director. "If we do not control it, organized crime and the pimps will take over."
Slightly more than 52 percent of Zurich's voters approved of plans to introduce sex-boxes in a referendum in March 2012. The boxes cost about $2.1 million to install and $749,000 to run annually.
Switzerland's right-wing Swiss People's Party opposed the move, The Independent said.
"It will not work, either because the clients will not come or because the site will not be used by prostitutes," said party politician Sven Dogwiler. "It puts them in a cleaner environment but one which is subsidized by taxpayers."
In Germany, sex boxes have been operating in designated big-city areas since 2001 and reportedly led to a "considerable drop" in violence against prostitutes, The Independent said.