Environmental co-benefits of mass rapid transit system improvement initiative in Selangor, Malaysia

The world have gradually experienced the impacts of climate change due to increase in human population and activities. Transportation sector is one of the major contributors to greenhouse gas (GHG) emissions and other local air pollutants which are NO2, CO and PM2.5. In line with this issue, more cities in developing countries have taken innovative initiatives to create sustainable urban mobility revitalizing the role of their public transport systems. Co-benefits approach has been identified as a solution that aims to align climate change issue with local development goals. Implementation of co-benefits approach aims to strengthen policy making process, which is identified as being especially important in the context of developing cities. The aim of this study is calculating environmental co-benefits of modal shift by MRT. Emission inventories for CO2 and local air pollutants such as NO2, CO and PM2.5 were developed for road transport sector for year 2011 and were used as a basis to explore intervention that is likely to reduce air pollution and GHG emission in this sector. The current study also presents a methodology to measure the environmental co-benefits of transport initiatives, defined here as GHG emissions in conjunction with local air pollution in Selangor. The methodology adopted the co-benefit approach to estimate the environmental co-benefits of both air quality improvement and CO2 emission reduction generated by modal shift to MRT. According to MRT daily ridership, two main scenarios were defined to show modal shift to MRT. Scenario (a) when the car riders shift to MRT and scenario (b), is motorcycle user’s modal shift. Also this study used the maximum and minimum occupancy of cars and motorcycles to show the range of emission reduction in each modal shift scenario. One of the main ways that MRT can generate environmental co-benefits is to reduce car and motorcycle ridership. According to MRT daily ridership, certain percentage of cars and motorcycle are expected to be off roads in study area. This amount of reduction in vehicles on Selangor roads will lead to reduction of vehicle kilometere travelled and also the amount of reduction in emission of CO2 and local pollutants. Specifically, this reduction comes from avoided emission that should have been emitted by MRT passengers if they are to use their motorized modes (cars and motorcycles). Modal shift analysis identifies that scenarrio 1a recorded the highest reduction for all the pollutants. Values recorded include 4.56% for CO2, 3.55% for NO2, 4.01% for CO and 0.51% for PM2.5. For CO2 and NO2, reduction is directly related with changes in scenarios as one moves from scenario 1a to scenario 2b. While CO and PM2.5 reduction do not follow any direct sequence (from scenario 1a to scenario 2b). In all the scenarios, CO2 emission recorded the highest reduction followed by CO, NO2 and PM2.5. Lowest reduction was recorded in scenario 2b for CO2, CO and NO2 while scenario 1b recorded the lowest reduction for PM2.5. In this study also integrated modelling approach (MM5-SMOKE-CMAQ) was established and simulations on meteorological conditions, emissions, and air pollution dispersions were performed to show CO2 emission reduction through different modal shift scenarios across the study area. The study showed that the existence of MRT has potentially contributed to the reduction of global and local environmental pollution through mainly the avoided motorized trips by shifting to MRT particularly from cars and motorcycles.

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