Youngsters will have to use smartcards to travel free on London buses and trams in a crackdown on bad behaviour.
Youngsters will have to show their photocard on request
From June, 11 to 18-year-olds eligible for free travel must carry and validate an Oyster photocard on a reader.
The move comes after reports of youth crime on buses rose by 55% to 5,701 in the first year free bus travel for under 16s was introduced in 2005.
Transport for London said it would make it easier to catch those individuals who seek to abuse the scheme.
Anyone applying for free travel as of this week will be issued with a Zip Card.
Users will have to 'touch in' on buses and trams and are required to show their photocard when requested to.
Mayor of London Ken Livingstone said: "Free travel is a vital investment in London's future, making London accessible for thousands of families by improving young people's access to education, sport and leisure.
"Young people... should also be aware that any youngster that abuses this privilege, for example by anti-social behaviour, will have their card taken away."