Environmental impact of improved bus service in Dhaka city

Abstract

The pollution from transportation sector is one of the biggest hazards that people of Dhaka City are facing today. The inhabitants of Dhaka City are also more likely to suffer the detrimental health effects that can result from breathing polluted air, because they generally spend more time outdoors and are more likely to travel open motor vehicles. Recently improved bus service has been introduced in Dhaka City for the improvement of transportation and environment. This study describes the instantaneous concentrations of SO" NO" and CO in major roads of Dhaka City; amount of exhaust emission from different vehicles operating in Dhaka City and the impacts on air pollution due to introduction of improved bus service. Instantaneous concentrations of SO" NO" and CO were measured by 'EXOTOX-60' atmosphere monitor at 47 locations of Dhaka City's main roads. The maximum instantaneous concentration of SO, and NO, are recorded 0.7 ppm and 0.3 ppm respectively. Average instantaneous concentration of SO, and NO, are high at Gulistan and Mohakhali; where buses and other diesel fuelled vehicle operation is high. The maximum instantaneous concentration of CO is recorded 93 ppm at Science Laboratory. Concentration of CO is high where density of traffic flow especially car, baby taxi, tempo, and microbus is high. A large sample of the inuse vehicles of Dhaka City was tested by 'EXOTOX- 60' in order to determine SO" NO" and CO emissions of these vehicles. It is observed that SO, emissions of Trucks, Tempos and Double decker buses are relatively higher than other vehicles and the exhaust emissions are 5.98 gm/I, 4.78gm/l, and 4.25 gm/l of fuel consumption respectively. The emission of NO, of Tucks and Double-decker buses is also high and the exhaust emissions are 31.65gm/l and 30.8 gm/l of fuel consumption respectively. The emissions of CO from gasoline fuelled vehicles like Microbus, Tempo, Baby taxi is high and cxhaust cmlSSlOns IS 276.2gm/l, 268.3gm/l and 226.5 gm/l of fuel consumption rcspcctivcly. Total daily cmissions from motorised vehicles in Dhaka City arc SO,: 5.43 ton/day, NO,: 21.57 ton/day and CO: 215.34 ton/day. Bus and minibus contribute high cst percentagc (23%) of total daily SO, emissions from motorised vehicles in Dhaka City. Bus and minibus also contribute highest percentage (32%) of total daily NO, emissions from motorised vehiclcs in Dhaka City. However car contributes highest percentagc (40%) of total daily CO emission from motorised vehicles in Dhaka City. Impacts of improved bus service are determined by Multinomial logit model. For this purpose an extensive individual survey has been conducted for the users of different transport services. On the basis of this data, the multinomial logit model is calibrated. The calibrated model is then used to estimates the probabilitics of using different urban transportation alternatives before and after the introduction of improved bus service like Premium bus service and City Service of BRTe. The result of this model is then combined with the emission of different vehicles to estimate the change of pollutant emissions due to the introduction of these services. Model results indicate that due to introduction of improved bus service SO, emission is reduced by 12.26 % and CO emission is rcduced by 19.08 % where NO, emission is increased by 1.86%.