These car parks have privacy screens - "a bit like stalls", says Ms Timmermans - between which prostitutes can conduct their business in their clients' cars.

Security cameras monitor the car parks and social services provide advice, medical information and condoms.

"You can talk to a social worker, you can get a shower, a cup of coffee, things like that," says the ICRSW's coordinator.

"I have never heard of anyone ever being hurt, or at least seriously hurt, in a zone."

According to the foreign ministry, "the introduction of these zones has significantly increased the safety of street walkers".

Government figures from 2004 showed that people driven into high-risk prostitution by drug addiction - a phenomenon common among EU prostitutes - made up only about 10% of all prostitutes in the Netherlands.

This is thanks to good drug outreach programmes, Ms Timmermans suggests.

And she adds that the attitude of the country's police - "they are great in general" - is also an important factor.