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Weekly UpdatesDISCUSSION AND CONCLUSIONS
For the first time in Africa, emission factor measurements were carried out on high loaded LDVs with diesel and gasoline engines. Similar to many developing countries, one of five vehicles in Algeria is a LDV, largely used for transportation of goods and people with an average annual mileage of 32,000 km (higher than the mileage in European countries) and an average lifespan of 10 yr. In addition, the number of LDVs is increasing. Although the results are representative of a local situation, they could also be valuable in other developing countries where similar conditions are occurring. The results should lead to more investigations in Africa on vehicle emissions in the future.
Because on-board emission measurement is a suitable technique for developing countries to conduct measurements at a low cost with affordable instrumentation, we used mini-CVS equipment. The conclusions are based on a small test fleet of eight vehicles conducted in the city of Blida, Algeria, but remain comparable with samples tested within different European studies. In addition, each vehicle was tested five times to reduce the uncertainty per vehicle. Results are representative of real in-use LDVs with high mileage in Algeria.
Nevertheless, some interpretations remain limited, in particular the comparison with the European ARTEMIS database: the average vehicle mileage of our sample was up to 696,000 and 163,000 km, respectively for gasoline and diesel engines, i.e., much higher than in Europe. In addition, our load rate is higher than in ARTEMIS; and the ARTEMIS model is not validated for load rate over 25% for Euro I diesel LDV category N1-I. The comparison should be more accurate if more data were available. Research on the influence of high load (>50%) on the cold and hot emissions should be fruitful because there are very few related articles published, and the high loads are very common in developing countries for all LDV categories.
Measurements also enable evaluation of cold-start excess of emission and of fuel consumption. In the case of gasoline engines, cold start emissions were 50% higher than hot emissions for C[O.sub.2], 80% for CO and THC, and 44% lower for N[O.sub.x]. They were 43% higher for C[O.sub.2], 78% higher for both CO and THC, and 40% higher for N[O.sub.x] for diesel engines. Fuel consumption excess at cold start was 67 and 49% higher for gasoline and diesel engines, respectively. Cold-start emissions were higher for our high-loaded vehicles than for the partially loaded vehicles from the ARTEMIS model.
Most emission inventories for pollutants or GHGs and air quality models for the African road transportation sector are based on the emission unit factors of European vehicles as input. In the case of many countries such as Algeria, the absence of emission standards for vehicles causes the age of the vehicles to be the main parameter used to find the corresponding European standards. The comparison of our data with European data enables evaluation of the European standard to which emissions of each tested vehicle correspond; vehicles of the same age show a deviation of zero standards for vehicles before 2001 and to one standard for those after 2000. Therefore, the major finding out of this work is that vehicles used in Algeria should be characterized by their true corresponding standard instead of referring simply to the year of the vehicle, which does not give any information on the engine technology and leads to high uncertainty. This issue could be addressed if Euro standards are adopted in the future in all the countries of the Maghreb region so that the governments can adopt a strategy of control and reduction of road vehicle emissions. In addition to this misallocation of standards, the emission factors do not consider local parameters of vehicle use and environment.
New vehicles are usually automatically associated with low emission levels without referring to any technology or standard. They are totally managed by electronic processes on the basis of high technology rarely available in developing countries. In such a case, the vehicle maintenance for emission reduction is hardly applicable. Facing this situation, it is crucial for these countries to adapt their regulations and to develop capacity building projects to strengthen their ability to maintain such vehicles.
Future research tasks should use a larger vehicle sample more representative of the national and even regional state of the fleet and local traffic conditions including all LDV categories (N1-II and N1-III) to obtain more reliable results. A quantitative evaluation of the traffic and of the driving behavior could improve selection of the representative trip. Emissions from the transportation sector are growing fast in developing countries. Appropriate emission unit factors are crucial for an accurate emission estimation, which constitutes the basis for policy makers to address issues regarding air pollution from traffic and to adopt efficient environmental regulations.
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