France, June 21 -- James Mwangi leaves his house in Kayole, a low-income neighbourhood in the east of Nairobi, at 5:47am every day, for the 20-minute walk to the bus stop.

Those 20 minutes require his full concentration - no matter how early the rise.

The walk takes him along a stretch of Kangundo Road where the pavement disappears entirely for around 400 metres, with a ditch on one side and moving traffic on the other, the ubiquitous boda boda motorbike taxis weaving in and out in both directions.

"The boda bodas come very close," said James. "You learn to pay attention all the time. You don't look at your phone."

Over the four years he has been making this commute, he has developed a mental map of where on his journey he is most lik...