Sex workers in the German city of Bonn are free to walk the streets, as long as they've purchased a ticket.

In an effort to regulate the sex industry (prostitution is legal in Germany) and to increase revenue for the city, officials in Bonn have begun requiring prostitutes to purchase tickets from newly installed sex tax meters. For €6  (or about $8.72), they can purchase a ticket that entitles them to a full night on the prowl. Those caught without a ticket face a reprimand and then a fine of up to $145.

Inspectors will monitor compliance -- not every evening but frequently, a spokeswoman told Reuters.

The meters are not the first attempt to regulate the 200 or so prostitutes who work in Bonn. The city has also constructed wooden garages known as consummation areas in which customers can have sex in their cars and relegated prostitution to certain areas of the city. Sex workers are also technically required to pay income taxes, but that can be difficult to enforce.

Ensures That All Pay the Tax

More than anything, City Spokeswoman Monika Frömbgen told The New York Times, the meters are intended to ensure that every citizen pays her fair share.

The women in the bordellos and the sauna clubs also pay the tax, and so should those working on the streets,  Frömbgen said.

In a time when German cities are groaning under the weight of billions in debt, the meters provide a relatively simple source of income that Franz-Reinhard Habbel, a spokesman for the German Association of Cities and Municipalities, told the Times he expects other cities to emulate.

A middle-age woman who gave her name only as Vero endorsed the idea, telling the Times that the meters were proper.

It's like rent, food or all the other things everybody has to pay for, Vero said.