The experiment in Switzerland's largest city began last August when the authorities opened Europe's first municipal drive-in brothel in an old industrial area to the west of Zurich, complete with helpful signposts and understated wooden drive-in "sex boxes".
Sex workers who agreed to move from their traditional haunts in the centre of the city were allowed to ply their trade there safely and with a minimum of fuss.
They did, however, have to get a permit and pay tax to avail of the drive-in's creature comforts, which include a laundry, shower and cafe facilities.
"The new regulation of street prostitution has attained its objectives of protecting the population and the sex workers," the city said in a statement.
Social services said that as well as protecting prostitutes, few neighbours were bothered by the comings and goings at the drive-in in the Altstetten district.
No increase in street walkers had been noticed in the two other districts of the city where prostitution is tolerated, they said.
Residents had risen up in protest at the number of prostitutes descending after dark on the Sihlquai, a main street near the city centre, and the authorities were also worried about human trafficking if the trade was left unregulated.
"The first year of the service has been positive," Zurich social services said in their statement.
The number of prostitutes working in the drive-in averaged 15 a night, half the number who worked the old red-light area before the city stepped in to regulate the business.
However, not everyone is happy, the authorities admitted.
Some prostitutes complain that their earnings have fallen and that they are too far from city centre bars and nightclubs.
Running the drive-in, which cost around two million euros ($2.6 million) to set up, has also proved more costly than originally thought.