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Sunday, March 9, 2014

Why Nairobi is stuck with matatu and traffic policemen

Many people in the so-called upper class think traffic police and matatus should be pushed off the cliff. In their view, traffic police and matatus make worse Nairobi’s traffic gridlock. But last week we had a chance to experience how commuting would be without traffic police or matatu. Simply put, for the “orderly and efficient” functioning of the city of Nairobi, traffic police and matatus matter.

Two decisions; asking the police to stop controlling traffic at intersections and increasing monthly levies charged to matatus inflicted anguish and frustration, to say the least, to residents and businesses who live and operate in Nairobi.

Nairobi County is trawling for revenue. And governor Kidero believes that policemen caused more confusion and gridlock at intersections, exacerbating traffic congestion. But this is a very simplistic reading of a complex problem.

In the typical Kenyan way, without analysis or evidence or consultation, we plunged into action. We got traffic policemen off the roundabout believing that traffic lights would work miracles. The result, one of the worst traffic gridlock ever. It was total collapse of mobility. All the major roads leading into and out of the city were chocked.
Consider that a vehicle coming into a roundabout with five roads radiating from it junction could turn one of four ways, with the widest being a 270 degree turn across two sets of light signals. You can bet that even the most sophisticated traffic signal cannot handle this efficiently. All it takes is poor judgment and lack of courtesy on the part of handful motorists at a roundabout to shut down the entire city. And they did.

Another reason why the network collapsed without policemen is because the system of traffic signals at most intersections are the fixed or static time control type. They are based on timers that have invariant intersection timing and phasing plans. What policemen bring to a static system is dynamic control. Policemen, in their limited way, adaptively alter phasing and timing in response to prevailing traffic conditions as best as they understand it. One of the great features of the dynamic police control system is that it can respond robustly to random incidents causing unusual demand at a roundabout.

Using a roundabout to manage road intersections becomes doubly complex with high vehicle density. Even in the best of times, without incompetent or discourteous drivers, a roundabout is difficult to maneuver. Invariably, a roundabout disrupts free flow, amplifies impedance thus exacerbating snarl-ups in rush-hour traffic. In my view the roundabout is an inconvenient monument, which presents a problematic structural constraint to efficient management of traffic flow in Nairobi. 

Last Wednesday matutu operators flexed their muscle by withdrawing their services to protest new parking levies. Whenever they strike, matatu operators also harass other motorists hence disrupting overall traffic flow. But the magnitude of traffic gridlock that ensues is associated with the matatus strike always astounds me. Why is there such a strong correlation between massive traffic jams and matatu operators’ strike? It seems counter intuitive because the expectation is that there would be less traffic, especially because matatus are off the streets, something we always long for.

In my view, this is what happens. Without the convenience of public transport, nearly all commuters who have cars will bring them out to the streets. My estimate is that one out of seven people who take public transport have a personal car but elect to take public transport to work. Hence, whenever matatus withdraw their services, there will be 2 private cars for every 14-seater matatu. All you have to figure out is how many people commute by matatu and how many matatus operate in the city of Nairobi. And it will scare the hell out of you how many private cars could potentially pour out into our constrained road network whenever there is a matatu strike. And rain, especially morning showers, also has the effect of getting lots of cars on the streets, just like end of the month when most private car owners love to flash their pay.

Without a publicly funded transit system, with modern high occupancy vehicles, we are stuck with the cargo minivans. But I must add that the proposed parking levies are provocative regressive taxes, which could make things worse for all commuters. Matatu operators offer a vital public service and must be treated with respect.

How about a combination of 4-way intersections, underpasses and overpasses, instead of the roundabout? Then we can keep the moronic static light signals and tell the police to stop messing around with traffic at intersections. 

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