Are speedbumps on Thika Superhighway worth it?
By MUNGAI KIHANYA
The Sunday Nation
Nairobi,
26 August 2018
Two weeks ago, I was
caught up in a traffic jam on the busy Superhighway on my way to
Murang’a. Actually, there were two snarl ups: the first one stretched
for 3km before reaching Juja and the second one about 3km after passing
the town. Both were caused by speed bumps!
I was delayed by
about one-hour delay in each of the two jams thus the journey that would
usually take me about 50 min took over three hours. I must admit that,
even though I use this road quite often, I have never encountered these
snarl ups before: I have only been reading about them in the press.
Now in August and
September 2009, I estimated in this column how much it costs Nairobi
citizens to sit in traffic jams going no where. By looking at the amount
of fuel wasted by the idling vehicles (Sh45bn) and the extra cost of
human resources arising from fatigued workers (Sh25bn), I arrived at a
figure of about Sh70 billion per year.
Even though I have
seen this number used in many reports, we must bear in mind that it was
calculated almost a decade ago and a lot of water has gone under the
bridge since then. Traffic is worse today that it was then and the unit
cost of everything has gone up.
Nevertheless, I think
it should serve as a wake-up call for the Kenya National Highways
Authority (KenHa) and Kenya Urban Roads Authority (KURA). These two
institutions must serious rethink the use of speed bumps.
In December 2016 I
discussed the science of designing speed bumps and warned that you don’t
just drop a lump of tarmac at the designated spot. The Kenya Bureau of
Standards requires that a bump should run over at least 10m along the
road direction!
Research in other
countries shows that such a bump slows vehicles to about 50km/h. At the
bare minimum, this is the type of bump that should be on highway.
Unfortunately, what we have on the Thika Highway are steep obstacles
that slow the traffic to under 10km/h!
The net result during
peak flow hours is that many vehicles come to a complete stop. I
discussed how this occurs in my articles of December 2016 and July 2018.
On the fateful day
two weeks ago, the queue of traffic stretched a total of 6km (3km before
Juja and 3km after). Allowing about 5m of a lane space per vehicle, this
works out to about 1,200 vehicle per lane.
The highway has five
lanes on this stretch: three on the express carriageway and two on the
side. But Kenyans being Kenyans, created two extra ones making a total
of seven. Therefore, there were about 8,400 vehicles in the queue!
This state of affairs
lasted about four hours – from about 11am to 3pm. If anyone from KenHa
or the ministry of transport is reading this, please ask yourself: are
the speed bumps on Thika Highway really worth it?
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