Asessment of Smoke Emissions Generated from Freight Vehicles at Idling Conditions in the City of Addis Ababa

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Addis Ababa University


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- iii 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.



Road and Transport Engineering