Asessment of Smoke Emissions Generated from Freight Vehicles at Idling Conditions in the City of Addis Ababa
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Date
2016-06
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Addis Ababa University
Abstract
Vehicles are the major sources of air pollution. In the developing world old aged
vehicles are one of the main reasons why vehicles emit pollutant gases to the
environment. The poor transport planning and traffic management systems leading to
traffic congestion and hence idling, on the other hand, is the other major reason
aggravating emission from vehicles. Vehicle related emissions are known to cause
stroke, cancers including childhood leukaemia, lower IQ levels in children and adverse
reproductive outcomes, low birth weight and premature birth and respiratory diseases
(Suglia et al., 2007).
The objective of this research was to quantify the smoke emissions from tailpipes of
diesel powered freight vehicles when they idle because of congestion & red light traffic
stopping in the city of Addis Ababa; and the relation of these emissions with vehicles
age. Considering the patterns of freight movements in the city of Addis Ababa, freight
vehicles that entered through the Djibouti Mojo corridor during the year 2015 were used
for the analysis as 95% of import commodities is through this route.
The major freight destinations in the city were identified to asses and analyze the idling
situation on the routes from the entry point to the different freight destinations in the city.
An empirical model was developed that combined data of Average Annual Daily Traffic
of Freight Vehicles, freight destinations of the vehicles, idling times spent by vehicles on
the selected freight routes of Addis Ababa and smoke densities of smoke emissions
from freight vehicles.
For the completion of analysis, two types of field measurements were performed. One
was to quantify the idle times on the different routes towards the major freight
destinations and another was to simulate actual road traffic idling at a measurement site
and measure the smoke produced from sample freight vehicles per idle situations;
referred as „stop and go‟ scenarios, by the use of a smoke measuring instrument called
opacity meter .
It was found that the age of the freight vehicles in the city of Addis Ababa is a major
factor for the emission of smoke from tailpipes. Vehicles‟ age was correlated with smoke
emission with a high correlation constant of -0.8. Average opacity values of 80%, 73%
21 % and 8% were obtained for the model year groups of 1959-1991, 1991-2000, 2000-
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2010 and 2010-2014 respectively from which the opacity values for the vehicles of pre
1991 vehicles resulted in much higher values than the standards of the US
Environmental Protection Agency i.e. 50 %. The computed average smoke density from
the freight vehicles resulted in a value of 7.6 meter -1 which is very much higher than the
threshold set by the standard of the European Union (EU VI). The result from the smoke
emission due to idling on each of the routes to the freight destination computed by the
empirical model was found to have increased with 93% from the calculated value on the
empirical model using the threshold set by the standard of the European Union (EU VI).
It was concluded that the level of smoke emissions from freight vehicles in the city of
Addis Ababa is very high to cause deleterious impacts on the health of the city dwellers
and also on the environment. To tackle the problem, old aged vehicles should be
banned from import, optimized traffic management systems should be effected,
integrated traffic and environmental laws should be formulated and implemented and
stringent laws on smoke emissions should also be formulated and executed.
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Road and Transport Engineering