probably means the start up aesthetics where the road looks very
If one looks at the
finish on most of the roads done by Chinese contractors one is
left wondering what we used to accept in the past and who had
set those standards.
One thing I am sure
about is that the Colonial government was not to blame.
Most of the roads
built in the pre-independence period continued to provide good
service without all the obvious wear and tear we see more and
more of today.
The first eyesore
that one gets on the more recent roads is the furrowing or
channelling of the road.
This is where the
ruts develop on tarmac in the areas that the tyres of vehicles
run most of the time.
These have developed
on many of the recently done roads both in Mombasa and Nairobi
and indeed across many roads in the country.
They ruts tend to be
on the main highways in to and out of county headquarters where
the roads are tarmacked.
The ruts are also
conspicuous where there is an incline on the roads.
Here in Mombasa the
most obvious example of this is when one comes off the Makupa
causeway on to the island.
As one begins to
climb up to the island one begins to feel the ruts especially in
small saloon cars as the steering becomes problematic.
Soon one can
actually see the deformed road surface, especially as one
approaches the roundabout.
But why the rutting?
There are two main
causes of rutting in roads.
The first and most
fundamental one is the condition of the substrate.
This is an inherent
quality of the design and construction of the road.
If the substrate is
not properly designed taking into consideration the type of
soil, the drainage requirements and the loading, the substrate
will not be able to bear the load and will start sinking.
Substrate failure is
almost terminal for the road and the corrective action would be
to rebuild the road from the foundation.
This is the most
expensive type of failure and can be seen in many parts of
There are several
sections of road between Miritini and Mazeras that perennially
fail due to this fact.
They have bad design
considering that the locations are prone to flooding, have
underground seasonal rivers or are natural wetlands.
Sometimes it is not
the design that was faulty.
What has tended to
happen is that the road is designed assuming certain conditions
and these could change significantly if, for example, the zoning
laws are not adhered to yet the design assumed that the zoning
laws would be followed.
By changing the
environment around the road, it could be that the drainage of
water is directed to an area that cannot cope with the
additional loading so undermines the substrate.
The roads instead of
being roads could become the drainage channel as there is
nothing else that allows water to flow freely.
An example is the
perennial flooding that happens on the road section between
Kengeleni and Ratna Square in Kongowea area.
This section of road
has been flooding for the last thirty years every time it rains
purely because of the building up of the area and the
channelling of all the drainage water onto the road.
The road itself has
not been redesigned to accommodate the changes in the
environment around the road and we continue to see degradation
of that road every year.
We re-carpet and
re-carpet but the same problem occurs year in year out.
We are not
addressing the basis problem that is the accumulation of water
which has seriously undermined the substrate of the road.
This leads to
rutting of the road over time especially with higher traffic
density and heavier trucks.
The second major
cause of rutting is the quality of material used to apply the
The temperature of
the road surface can get quite high especially when it is
temperature highs in Kenya can reach the mid thirties (in
When the atmospheric
temperature is at this level, the road surface can be almost
double that temperature so the bitumen that we use must be able
to withstand that higher temperature at the load for which it
The most common
bitumen standard used in Kenya – which is the drummed bitumen
commonly called penetration 80/100 bitumen or also now known as
VG-10 works best at atmospheric temperatures between minus ten
and thirty degrees.
The next grade is
penetration 60/70 or VG-20 and this works between zero and forty
The grade after
which is penetration 50/60 or VG 30 works between ten and fifty
degrees centigrade. Kenya needs to make a change to the design
standards of roads and move to at least VG 20 or preferable VG
30 as the standard.
This will ensure
that the softening of the road surface will be minimised due to
the action of loads and shear caused by tyres.
There are many roads
in the country where rutting is as a result of this
inappropriate standard of bitumen.
There is also the
reality that on inclines the weight distribution shifts so that
the axle load is actually higher than what the design takes into
So, in order to
avoid rutting it is important that the design is done properly
and the materials specified are correct for the conditions that
obtain in Kenya.
As Kachumbari says,
we need good roads and we must give the preferred outcomes a