Authorities in Zurich have unveiled drive-in sex chalets in a bid to make prostitution safer for both sex workers and customers.

The nine garage-style structures, which are located in a former industrial zone in the west of the city, will be unveiled later this month at a cost of £1.5 million. They will be in use daily, from early evening until 5am.

Prostitution is legal in Switzerland and Zurich revealed its intention to open the 'sex boxes' in November after residents approved the plan in a referendum vote.

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After passing a checkpoint drivers will follow a marked route past a line of 40 prostitutes before selecting one and negotiating a fee.

The customers will then drive into one of the wooden sheds, which have safe sex posters hung on the wall.

Sex workers will have to buy a 'work ticket' each evening costing around £3.50 for each night that they work. They will also have to register with a health insurer.

Pedestrians or motorcyclists are not allowed and the wooden sheds are equipped with panic alarms which can be activated if the customers or prostitutes feel in any danger.

Once the sex chalets open Zurich men will no longer be allowed to solicit sex workers outside the group of boxes or two other approved zones.

The new plan is part of an initiative to place order on Switzerland's growing sex trade, protecting workers while also keeping them away from the centre of the city and residential neighbourhoods.

Welfare department official Michael Herzig told The Telegraph "We want to regulate prostitution because until now it was the law of the jungle."

"It was the pimps who decided the prices, for instance. We are trying to reach a situation which is better for the prostitutes themselves, for their health and security and also for people who live in Zurich," he added.