Recent figures suggest there are as many as 200 prostitutes working on the streets of Bristol.
New laws mean curb crawlers can now be prosecuted
Almost all are funding a crack or heroin habit which is costing them on average £800 a week.
This leads to as many as 500,000 sex encounters in Bristol each year.
The BBC investigated the sex trade in one area of the city - Easton.
On one day - by 1200 BST - it found six women waiting for passing trade in broad daylight.
Drug dependence is now the major reason behind prostitution in Bristol
They were standing in full view of a primary school.
Lisa Stanley, 24, agreed to talk.
She has been working in prostitution for eight years.
"It varies as to how many men I have sex with in a day. Anywhere between one and 15," she said.
"My habit is heroine and coke and I need at least £200 a day and I make it. It's too easy.
We... have twice as many women wanting to come into treatment as we have money to treat them
Bristol Drugs Project
Police are targeting kerb crawlers in an effort to tackle prostitution, but robberies and burglaries often take higher priority.
This often means drivers are in a hurry - giving women less time to check out who they are about to drive off with.
BBC Points West reporter Scott Ellis said: "What is different in the city now is that women are turning to prostitution because they are addicted to drugs.
"The big problem is the increased use of crack cocaine in Bristol over the last three years.
"It is very addictive and very difficult to treat."
Maggie Telfer, from the Bristol Drugs Project, agreed.
"We are tackling the major underlying cause of street prostitution - drug dependence," she added.
"We have a new treatment programme, but we also have twice as many women wanting to come into treatment as we have money to treat them."
She says assaults on adult woman are common, and that more young adults and children are beginning to find themselves drawn in.