Is Nairobi's double decker road sustainable?

The elevated uhuru Highway 

THE GOVERNMENT OF KENYA plans to construct a 12Km over-pass over Uhuru Highway at a cost of US$200m. The World Bank funded project, will also include building by-passes in Kisumu city and Meru town. 

The two by passes will cost an estimated US$60 million.Therefore the entire project will cost US$260 million of which the Kenya government must raise 20 per cent or US$52 million. Other components of the project include construction of an additional Lane from Nairobi West lands suburb to Rironi in Kiambu County. It will also include service roads.

The project is variously justified as a solution to congestion on the Northern corridor and as a panacea to slow movement of traffic between JKIA and its customers to the West of Nairobi.  And critics have raised the red flag wondering if the road is necessary now or in the next 15 to 20 years.  The critics have a point as there are other on-going transport infrastructure developments in the city that aim to ease congestion in the CBD.

The on-going projects especially the Southern by-pass and the construction of a rail link from the Airport to the city are also designed to ease traffic congestion in the city.
 The US$235 million Southern by-pass now under construction ill divert all traffic towards western Kenya from Mombasa side from Uhuru highway. 

 The 49 KM road links Mombasa road at St. James Hospital and terminates at Rironi where it joins the Nakuru road.  Further, the by-pass has a direct link road to Waiyaki way at Westlands from Kileleshwa estate.

In effect, on completion of the Southern by pass, Uhuru highway in whatever form will not be part of the Northern Corridor.

In addition, the  Kenya Railways Corporation  has advertised for a contractor to build a 7Km railway line linking Jomo Kenya Airport with the city as part of the greater Nairobi commuter rail service. 

 The building of the line will enable a high frequency, high speed train service that will cut travel time from the airport to the city center to 20 minutes from the current 90 minutes .

The project will include construction of inter-modal exchange for passenger traffic from Athi River and outlying areas. This means that the stations will also include a bus park and a a parking bay for private cars. Even car-owners can leave their cars parked at the Railway station, board a train to the CBD. Already the Syokimau station through which the line from the airport will pass is in place.

The total sum effect of these developments is to reduce traffic congestion in the city and also de-congest Mombasa road/Uhuru highway. This leads to the question: can the double decker road be sustained? In other words, will there be enough traffic to use the elevated road to justify the large investment?

JKIA Railway Line: To cut travel time to less than 20 minutes
Supporters of the project say yes. Critics differ. A road is sustained by demand, that is, by the number of vehicles that use it. The optimum demand for a single lane road is 1350 cars per hour both ways, working to about 18000 cars per 13-hour day.

  That Uhuru high way / Mombasa roads which are six lane affairs are congested means that the current usage is more than 3300 vehicles per hour both ways. Estimates put the traffic load per day on these roads are about 150,000 especially at peak hours. They are stretched thin hence the need for expansion of the road.  

A traffic count in 2004 established that 73.7 per cent of the traffic on Uhuru high way at Museum Hill was private cars. The same study established that cars comprised 77.7 per cent of vehicle population on the same highway at the Mombasa road. It is expected that the composition of vehicle population has not changed.

The southern-by pass was initially slated to be a toll road. Studies indicate that for a trunk road to be profitable it must have 13-hour traffic not below 20,000 vehicles. So we can safely assume that an estimated 18,000 vehicles will divert to the by-pass. The figure could be high given that the road cuts through the leafy areas of the city. It cuts through Ngong road, Hurlingham road and Westlands and adjoining estates. This means that the by-pass would ease traffic also on other intersections of the city.

Syokimau Railway Station: an inter-modal  station
  Critics also point out that the creation of Bus rapid Transport, which like the railway line is also a mass transit system, would reduce further the number of vehicles plying the city streets and hence the demand for roads. Consequently, they argue the elevated road project should wait for effect of the on- going infrastructure developments on traffic to be felt so that the need for another road is evaluated.  They say that the money would have been well spent in the construction of Outer-ring road that links Thika Superhighway to Industrial area and the Airport.

The critics caution against saddling Kenyan with debts for unsustainable projects. With the changing geo-political set up, Kenya is now well placed to attract funding for development project.  The east-West Rivalry on Africa has ensured that development finance is easily available. Kenya must leverage this advantage to develop useful projects.

One way of doing this, critics say is to evaluate the project on commercial lines to see if it is viable. If the price is not sustainable, then the project is not sustainable either.


  1. Excellent projects I feel! I think if this whole project is meant to quicken movement of people and goods and the country can manage the World Bank money then it is worth having it. In fact all cities built around the world had seen some kind of sucrifice on the part of citizens.

  2. Double decker roads are not build bang in the middle of the city. They destroy the value of the property along its route thus becoming an eyesore.
    Further the city is already ringed by by-passes diverting traffic from the same route. One wonders what traffic will be using the raod


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