Precipitous mountain roads, specially-modified bikes, and deadly consequences. Simon Maybin spends time with the young men who race down the steep roads of Colombia’s second city Medellin. Marlon is 16 and he’s a gravitoso - a gravity biker. He hooks onto the back of lorries or buses climbing the precipitous roads to reach high points around the city. Then, he lets gravity do its thing and - without any safety gear - hurtles back down the roads, trying to dodge the traffic. This year, two of his friends have died gravity biking and Marlon has had a near-fatal accident. But he’s not quitting. So what drives young men like him to take their lives into their own hands? And what’s being done to stop more deaths?

Presenter/producer: Simon Maybin

(Image: Marlon with his bike ready to ride back down into Medellín. Credit: Simon Maybin/BBC)