Imagine you are 10 years old.You live in a big city and want to visit your best friend, a five­minute walk away, and then you can go to the park, another 10 minutes ' walk.The problem is that there ' s a big dangerous road between you and your friend, and another between your friend ' s home and the park.When you ask your parents if you can walk there, they say no.But they are too busy to take you there themselves. Instead, you have a video conversation with your friend, or perhaps you play a video game on the sofa.You ' ve lost out on exercise and time outside, interacting with your neighborhood and, of course, play time with your friend.This is the reality for many kids today — but it doesn ' t have to be this way. Tim Gill, the author of Urban Children: Gro w ing Up in a Risky Society, says a child­friendly city is one that allows “everyday freedom” , so a child can spread their wings as they grow. “ It ' s not enough to just talk about playgrounds and nice, pretty public spaces.That just creates play places they have to be taken to by adults , ” says Gill. “ Society ' s mistake is that our planning systems just focus on cars, house­building and the economy ( 经济 ) — rather than the environment, health and quality of life , ” argues Gill. “ You won ' t find any urban planners who can disagree with that .It ' s because our decision­makers fail to look beyond the next two or three years. ” Tim Gill lists five challenges for urban children in his book: traffic and pollution; high­rise living; crime and social fears; inadequate and unequal access to the city. Designing cities with young people in mind — particularly outdoor spaces that encourage safe movement and social interaction — stands to be an issue of growing concern globally.By 2050 around 70 percent of people will live in cities, and the majority of them will be under 18.Today, over a billion children are growing up in cities.