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The State of Dhaka’s Traffic-related Pollution

by Md Masud Karim
**As we are plagued with severe air pollution problem in Dhaka, what we need, among other steps, is to find and alternative equivalent of auto-richshaw, that is environmentally friendly and is able to provide door-to-door service.
Motor vehicles contribute significantly to emission inventories in certain regions, especially in urban areas. The pollutant species most often of concern with respect to transportation facilities are carbon monoxide (CO), hydrocarbons • photochemical oxidants e.g-. ozone (03). nitrogen oxides (NOx). particulate matter (PM), and lead (Pb). In spite of great improvements in most developed countries due to reduced use of leaded fuels, highway emissions of lead remain a persistent air quality problem. Recent studies indicate that motor vehicles are also a major or primary source of other toxic air pollutants including 1.3-bu-tadiene. benzene and a number of carcinogens, associated with particulate matter.
As the vehicle fleet continues to grow, motor vehicle emissions and the products of their transformation in the atmosphere, random acceleration-deceleration due to non-motorised vehicles in developing countries, are becoming increasingly important contributors to nearly every major air pollution problem facing the world today In urban areas, where more than 70 per cent of the population live, levels of motor vehicle-related pollutants frequently exceed internationally agreed air quality guidelines.
In developed countries, governments have fought for clean air by regulating all major and many minor sources of air pollution. Industrial emissions have been significantly reduced. As a result of new motor vehicle emission standards introduced In 1988, new vehicles in developed nations are 90 per cent cleaner than those manufactured in the 1970s. However, despite those substantial efforts. we continue to be plagued with air pollution problems. Major issues are the two-stroke engines plying Dhaka's street, heterogeneous flows of traffic and our continued and growing reliance on the private car. It is not out of context to mention here that the two-stroke en-gnes (baby-taxis) moving in haka city are simple modified form of an Italian model of 1960s. It is estimated that a baby-taxi emit 30 times more pollution than a normal car In providing a very simple logic, we can replace a baby-taxi by 30 cars in Dhaka, considering the environmental point of view. Though baby-taxi size is a suitable mode for Dhaka s street geometry.
In Bangladesh, severity of pollution occur due to the nigh content of lead in gasoline, large number of high polluting vehicles, impure fuel, inefficient land-use, and overall poor traffic management The pollutants of concern for Bangladesh are leaded fuel, particulate matter. dust, oxides of nitrogen and sulfur dioxide.
Dhaka had the highest lead pollution in the world for a part of the year 1996, scientists at the Bangladesh Atomic Energy Commission (BAEC) observed (http://www.bangla.net/) A 17-month survey study by BAEC scientists detected 463 nanogram of lead in 1 cubic meter of air over Dhaka during the dry months (November 5-Jan-uary 6) In Bangladesh all vehicles use leaded fuel because the country’s only refinery is n't
able to produce lead-free fuel. The higher share of SOx emissions from automobiles in Bangladesh is due to the poor fuel quality and the extensive use of diesel-powered. In some cases impure diesel, vehicles.
Air Pollution in
Bangladesh
Emission inventories of NOx and SOx have usually been made on national basis mainly for general administrative purposes and public Information, Sstematic data published for e use of the scientific data is rather scarce. Nationwide SOx and NOx were calculated based on sulfur content and statistics of fuel consumption estimates of emission factors specific to individual source categories over time. Developing countries like Bangladesh is characterised by a rapid Increase of energy consumption accompanied by a rapid growth of population and economic activities. Thus the increasing contribution of atmospheric loads of SO2 and NOx to global climate change is anticipated and it is really necessary to quantify these emissions in a hurried manner. A national steering committee should be established with local and expatriate Bangladeshi experts to deal with the problem.
Air Pollution in Dhaka
Dhaka, the capital city of Bangladesh, has grown into a busy city of about 6.5 million people with an area of 815 km2 Dhaka city has heterogeneous traffic flows — as of 1996 an estimated total of 168,718 automobiles are on the roads A substantial part of total traffic is non-motorised vehicles that enhances severe congestion and pollution problem, especially at road intersections Around 80 per cent of total trips in Dhaka city is comprised of non-motorised transport (NMT) and only 5.9 per cent trips are made by motorised transport (MT). Average trip length of MT is 27 minutes Trips made by public transport, especially buses are very low — only 0.9 per cent The maximum trips of vehicle modes are made by using rick shaw is 43 per cent. Though It is very difficult to quantify pollution contribution from such heterogeneous traffic combinations. the influence of non-motorised transport on pollution are averaged upon the pollution considering the average speed of traffic flows.
Trends in National
Emissions
The primary objective of this section is to provide cur-
rent estimates of nationwide emission for two major trans-SjrtaUon pollutants: SOx and
Ox Estimates are presented for 1981 to 1991 to give trends for national air pollutant emissions. An average of about 15 per cent energy consumed in the transport sector at national level A maximum of 18 per cent transport energy consumption occurred in 1990. An average of 34 per cent NOx emission exhausted from transportation system to total emissions. On the other hand, the contribution from transportation. SOx emission averaged 47 per cent. Such high share of SOx emissions from automobiles is due to the high content of sulfur tn petroleum products and extensive use of diesei fuel
Emissions in Dhaka
Metropolitan
The average daily traffic
emissions of NOx. HC, CO. PM and SOx are presented for Dhaka city. They are estimated based on the emission factors and total dally fuel consumption from 1981 to 1996. Data for fuel consumption is available till 1992, on the other hand total daily trips are available till 1996, an average growth rate equals to that of daily trips are taken to estimate current trends in fuel consumption. The average daily trips of all modes of transport, average trip duration. mean running speed, and emission factors of kilometerage travel are also accounted for in estimating dally emission.
Emission factors for kilometerage travel are always con sidered for 5 to 6-year- old model vehicles Because most of the vehicles imported in Bangladesh are reconditioned automobiles. Bangladesh only allows to Import maximum 5-
year-old vehicles. For example, in estimating emission in 1988, we used emission factors for 1981 vehicles. There was a fall tn trends of fuel consumption in 1989. as a result sharp fall in emissions was observed. In 1987 and 1988 there were severe floods affecting about two-thirds of the total area inflicting severe damages. Capital stock losses were well over 8100 billion which seriously affected the national economic growth.
Emissions of nitrogen oxides are produced largely by transportation sources. Emissions of NOx have steadily increased over the period from 1989 to 1996 as the result of increased fuel combustion. From 1981 to 1988. the size of the change in emissions fluctuated. Transportation sources are the largest emitters of carbon monoxide. Major Increase in emissions occurred in pre-1989
period. in 1986. about 91 thousand tons of CO emitted from transportation systems as the result of increased motor vehicle travel.
NO2 Concentration -^-.i»Dhaka
Interest in ambient NOx concentration has increased due to health effects of this pollutant and its important role In the formation of photochemical oxidants. NO2 is also a precursor to species such as nitric acid and nitrate aerosols which contribute to acidification of the environment. In November of 1996. a field study conducted by the author to measure ambient NOx (NO. NO2) concentration in 28 street locations in Dhaka city. Two zones were divided to identify the severance of the problem of NOx. The high concentration locations (black spots). Zone I and less polluted areas. Zone II. Zone I is identified as the locations where NO2 concentration exceeded 40 ppb, and consequently Zone II is those locations less than this level. Among 28 street locations. 16 of them identified as the black spots, where NO2 concentration observed more than 40 ppb. Maximum concentration observed 64 ppb at Mailbag area, followed by Bijoynagar 63 ppb, and then Shapla Chattar 57 ppb. The hourly average traffic flow from Mogbazar to Mailbag link was 2613 veh/h with an average speed 22 km/h. Paltan to Bijoynagar link 2920 with an average speed 22.85 km/h. and Bijoynagar to Kakrail link 2711 veh/h and mean vehicle speed 24.62 km/h.
Conclusions
Bangladesh has yet to be implemented a National Air Quality Standard, there are no detail air quality regulations based on which Environmental Impact Assessment could be done. Very few works have been done on air quality measuremenu and national air pollutants estimates In Bangladesh. Few recommendations are:
• A national steering committee constituting experts is urgently needed to be established to cope with the problem.
• Formulate guidelines for policy makers, city planners, traffic engineering practitioners towards mitigating traffic pollution problems and make recommendations for setting National Air Quality Standard
• Auto-rickshaw (AR) should be restricted in Dhaka city. Consequently, an equivalent and efficient alternative mode of transport should be initiated in Dhaka, so that, those who are importing AR. driving AR can do the same for the new mode of transport. Current initiative of taxi-cab is appreciating. However, the pre-conditions. NEW and 2000CC car seem to be policy makers ignorance In understanding modal ' choice in Dhaka. A pre-condition is really necessary that is — not the diesel car". As we are Wied with severe air pollu
problem in Dhaka, what we need is to find an alternative equivalent of AR. that is environmentally friendly and is able to provide door-to-door service.
The writer is a Consulting Engineer. Dainicht Consultant Inc.. Japan.