Image caption Most women have experienced leering or suggestive remarks

From whistling to catcalling, and even groping, street harassment is an everyday reality for many women around the world. But now a new wave of feminist groups are organising to stop it.

One dark evening in south London, a group of men slow their car behind a young woman walking alone.

They call out to her, propositioning her to get into their vehicle.

She keeps walking, heart rate quickening, ignoring their lewd comments. The men continue to follow her and their words get more aggressive.

Just before she reaches the nearest underground station, she's had enough. She strikes the men's car and flees down the station steps.

In a rage, the men leap out of their car, chase her, grab her by the neck and pin her to the wall.

This was an experience that drove Vicky Simister to take action and found Anti-Street Harassment UK.

It's one of a new wave of groups tackling an age-old problem. At the forefront of the movement is the international Hollaback! campaign group. Having started in the US, it will open another dozen chapters next week, everywhere from India to Croatia.

Hollaback! and Anti-Street Harassment UK offer forums in which women can share their experiences, share photos of their harassers and view maps of where previous incidents have occurred.

Most people would recognise that what happened to Simister was totally unacceptable. But what if the incident had not escalated into violence? What if Simister had not been followed? What if it was just suggestive remarks shouted across a street?

Day in and day out millions of women are whistled at or shouted at on public streets. It can be unpleasant, and for Hollaback! activists it's all part of the nasty business of street harassment.

They're in a long tradition - going back to the 1970s Reclaim the Night movement - of trying to make the streets safer and more pleasant for women. Much has been done, in the West at least, to deal with harassment in the workplace, but the streets remain a different proposition.

There's no suggestion that most men carry out harassment in the street, but occurrences are widespread.

In an online study by stopstreetharassment.com, 95% of respondents said they had been the victims of leering, honking or whistling and a large proportion have been groped or grabbed in public.

Around the world Public sexual harassment known as "eve teasing" in India

In the US, Reclaim the Night campaign started in the 1970s with marches against sexual violence and pornography

In Japan, groping on the subway has been a problem for many years

Mass sexual assault on reporter Lara Logan and other incidents highlighted issue in Egypt

Emily May, the founder of Hollaback!, is on a mission to stop the harassment.

"It stems from a broader culture of gender based violence," says May. "To shift that culture it takes people standing up and saying street harassment is not OK because most people in our society don't want it to exist."

When a man shouts "hi gorgeous" or "come over here love", the recipient of the comments might be annoyed, but the remarks are often disregarded by bystanders, so the problem goes largely unaddressed.

"Women are advised to ignore it, and we don't speak up about it. Therefore, these men keep on doing it and push boundaries further and further," says Simister.

And it's dangerous because it's difficult to distinguish which men simply shout and which ones may use catcalls as a gateway to violence or sexual aggression.

Men have been indoctrinated into it, and it's been a privilege for them to walk down the street fantasising about women Maggie Hadleigh-West, Activist and film-maker

"If a guy is checking out a woman it's annoying, but that's how sexual predators who are honing their craft test how far they can go," says activist and filmmaker Maggie Hadleigh-West.

And street harassment varies from country to country. In the UK and US, most women will experience only shouting, but in many parts of the world street harassment can escalate to groping and more frequent public sexual assaults.

In India it is euphemistically referred to as "eve teasing", in Japan groping on the subway has long been a problem, and the attack on Lara Logan in Egypt gained international attention.

But why do some men harass women in public?

Street harassment occurs because our society has always allowed it and dismissed the behaviour as "men being men", says Hadleigh-West.

"Culturally, men have been indoctrinated into it, and it's been a privilege for them to walk down the street fantasising about women. The culture hasn't checked the behaviour."

Image caption Some cities have implemented women-only subway cars to stop harassment

Because society has perpetuated this as a cultural norm, men tend to engage in street harassment as a way to prove their masculinity, says Northeastern University associate professor of sociology Kathrin Zippel.

"Often times it's not really about the women, it's just about the men performing masculine acts for each other and establishing a pecking order amongst themselves. What is really going on is the dynamic among men."

So can the leering, the catcalls and the grabs ever really be stopped?

"Some activists have targeted city planners and the public transport officers to make the case that women should not face harassment in the streets," says Zippel.

In response some countries such as India and Japan have created women-only subway cars.

But critics say this sort of measure is only a temporary fix.

"I find recreating segregation in public to be highly problematic. In the short term it might be a good solution, but they also notice that if women step onto mixed cars there are less women on them and the ones who are experience more harassment," explains Zippel.

To take the burden off women, the founder of stopstreetharassment.com Holly Kearl suggests that councils gather survey data on assaults and sexual harassment and then work out what kind of responses work.

On college campuses in the US officials addressed safety concerns by adding more lighting, installing safety phones and redesigning bus stops

Not all men impose unwanted attention upon women, and Kearl agrees that it's important for these men to join in the movement to stop street harassment.

Image caption The attack on Lara Logan focused attention on Egypt

"We have to engage men. In our society it is easy to sexually objectify women, so it is important to make men realise that every woman you harass is someone's mother, sister or daughter, and she is a person who deserves respect."

When men take accountability for the actions of themselves and their peers, it helps to create a cultural shift in attitude. If a man feels that catcalling won't be accepted by his peers, he is less likely to engage in the behaviour.

"When men are made aware of it, hopefully by women they love, they can listen, hear and see what is going on. It becomes an individual responsibility and men really do care when they get it," says Hadleigh-West. "I have seen enormous change happen in the consciousness of men."