It’s frustrating to be stuck in traffic. Listener Collins from Nairobi, Kenya, spends at least three hours a day in traffic and he counts himself lucky. Many of his friends will easily spend six hours in traffic jams to get back and forth from work. Collins wants to know whether there is hope for his hometown – has any city managed to eliminate the worst of the traffic hot spots and how did they do it? Collins is not alone in his frustration. CrowdScience finds that congestion plays a major factor in the happiness and health of urban citizens. Commuters have been measured to have stress levels equivalent to that of riot police facing angry protesters. So should our cities cater less for cars and what are the alternatives? Presenter Gareth Barlow heads to Copenhagen to meet the politicians and urban designers who have transformed the Danish capital from a city for cars to one for bikes and people. Presenter: Gareth Barlow. Produced by Louisa Field (Photo: Afternoon traffic along Likoni road in Nairobi's Kilimani susburb. Credit: Getty Images)