South Harrow people can now see exactly where is covered by a new dispersal zone brought in to tackle anti-social behaviour.
Police have been given additional powers to tackle nuisance youths in South Harrow after complaints about unruly behaviour.
Within the zone, which covers Northolt Road and neighbouring streets, officers can break-up groups suspected of anti-social behaviour and ask them to leave the area.
Young people under the age of 16 who are unaccompanied by a responsible adult between 9pm and 6am can be returned to their home.
Failure to comply with police could lead to a fine, up to three months' imprisonment or both.
To deter youths from gathering, thirteen six-foot high steel gates will be put up at the end of every alleyway along Northolt Road from Roxeth Grove to Parkfield Road.
The zone will be in effect for six months and has been introduced by Harrow Council and police after residents and businesses complained of crime and anti-social behaviour.
Harrow Council leader and Roxeth Ward councillor Thaya Idaikkadar said: "Those who choose to behave in an aggressive and threatening manner can make people feel anxious and nervous – and can even drive residents and visitors away from an area.
“These powers will allow the police to nip this sort of behaviour in the bud before it escalates and causes more trouble.”
The scheme has been brought under the Anti-Social Behaviour Act 2003 and will run until June 11, 2013.