The new posters - a series of three - are the latest phase of the "Shattered Lives" campaign by TfL, which began in November with the launch of a cinema ad, and will extend to radio and TV advertising in March.

The "Shattered Lives" campaign, part of TfL's award-winning "Don't die before you've lived" series of adverts, aims to alert teens to the consequences of not paying attention when near to or using roads.

Young teenagers (11 to 14-year-olds), are more likely to be involved in a road collision than any other age group, thought to be due to the increase in independent travel that tends to accompany the move to secondary school.

The three different ads feature a future football player, high jumper and lead ballerina flying through the air after stepping out into the path of a moving car.

All the ads feature the line "Don't die before you've lived" and the message "Every day a teenager is killed or seriously injured on London's roads".

Ken Livingstone, Mayor of London, said: "Road safety is improving in London, because we are spending more money on doing the things which we know save lives.

"The number of children killed or seriously injured on our roads has fallen by 58 per cent compared with the late 1990s.

Redoubling our efforts

"Nevertheless, one death is one too many and we are redoubling our efforts to meet even tougher targets."

Jenny Jones, the Mayor's Road Safety Ambassador, said: "Shattered lives is a warning about broken dreams and loss.

"Every time a young person is run over, our world loses a bit of its future.

"London has one of the best records for reducing road casualties in the country, but that means nothing to the parents and friends of a young person killed on our roads.

Reducing casualties

"That is why London has higher targets for preventing road casualties than the rest of the country and why we will do everything necessary to end the tragedy of shattered lives."

David Brown, Managing Director, Surface Transport, TfL, said: "We have made great progress in reducing casualties on the roads, particularly among young people, but there is a long way to go.

"It is particularly tragic when a young person is killed or injured on the roads, and this campaign warns them not to shatter their dreams by being careless near busy roads."