Nairobi is the world's fourth-most congested city, according to IBM's Commuter Pain survy in 2011. This congestion is costing the city both in terms of road accidents and productivity. It's estimated that the city loses about $578,000 per day because of its congestion, according to a report by Bloomberg.com.

Kenya's projected 4.3 percent annual rate of urbanization from 2010 to 2015, when 12 million of its people will live in urban areas, is more than double the global average of 2 percent and above the African average of 3.6 percent, according to the United Nations.The city has road capacity for a population one-third its current size of 3.1 million -- a figure forecast to balloon to 40 million by 2050, the equivalent of the entire country's current population, Nairobi Governor Evans Kidero said in a Feb. 12 speech, according to the Bloomberg repot.

A more than doubling of the number of vehicles on Nairobi's roads since 2012 to 700,000, hasn't been matched by "infrastructure and traffic management" and the city must prepare for as many as 9 million car users by 2050, according to Bloomberg.

Efforts are under way to relieve some of the congestion. A freeway designed to divert traffic from the congested city center is nearing completion. However, some of the development funds are being siphoned away by graft, according to Bloomberg.

To aid in easing the congestion, the city has installed programmed traffic lights, speed monitors, and closed-circuit cameras, according to Bloomberg. Part of the problem, however, is the fleet of 20,000 privately owned minibuses--known locally as matatus--that regularly disregard traffic laws.