Carbon footprint of urban public transport systems in Indian cities

Investment in public transport is unarguably one of the most critical measures to be adopted by the Indian city authorities to tackle the issue of rising private vehicles, congestion and pollution. A large number of Indian cities are in the process of planning/implementing public transport projects, mainly – city bus system, bus rapid transit system (BRTS) and metro rail transit system (MRTS). Decisions related to the development of a particular type of public transport system are primarily based on technical and financial criteria. However, environmental factors are not given adequate importance while undertaking public transport projects.

The aim of the paper is to determine life cycle environment impacts of public transport projects occurring during all the three phases i.e. construction, operations and maintenance phases of these projects. The paper aims to validate that these impacts are important and need to be compared to make an informed decision about providing most environment friendly public transport system to the people.

Of the various methods of calculating carbon footprint of infrastructure projects, the authors adopted the life cycle analysis (LCA) approach. The ISO 14042 framework for LCA (cradle to grave approach) has been used for estimating energy consumption and carbon emissions of public transport projects (BRTS and MRTS) in India – case studies of Delhi Metro and Ahmedabad BRTS have been used.

The findings of the paper indicate that metro rail could be considered more efficient public transport system based on tail-pipe emissions. However, an evaluation based on life cycle of public transport systems indicates that a metro system generates more carbon dioxide (CO2) emissions/passenger kilometres (PKM) as compared to a BRT system. The same metro system is, however, more energy efficient [kilojoules (kJ)/PKM] for its full life period as compared to BRT system.

The results and methodologies adopted in the paper could be used to introducing life cycle impact considerations to bring about more robust understanding of the overall impact of a system/proposed infrastructure project. This paper helps to enhance the scope and not limit to just tailpipe or a particular city and help make informed choices regarding public transport systems based on the economic, social and environmental goals set by national, state or city governments.