Downtown Nairobi, Nairobi Area, Kenya, Africa. (Getty Images) By Haneen Khreis, Texas A&M University, and Mark Nieuwenhuijsen, Australian Catholic University, for The Conversation Kenya’s capital, Nairobi, is the second most congested city in the world. To reduce congestion, Nairobi County has proposed car-free Wednesdays and Saturdays in two…