Evaluation of sustainable urban mobility using comparative environmental life cycle assessment: A case study of Qatar

The transportation sector is responsible for impacting both human health and greenhouse gas emissions. The primary mode of transport in Qatar is private automobiles, which can have a significant environmental impact. One strategy for transitioning to a low-carbon urban environment is the Doha Metro Project, which aims to reduce emissions from private automobiles. The focus of this study is the development of comparative life cycle assessment models to quantify the energy output and emissions of two major transportation alternatives in Qatar—automobiles and metro—within gate-to-gate system boundaries that limit their operations. GaBi 6.0 software was used to model and quantify the environmental impacts per functional unit of passenger kilometers traveled. The analysis demonstrates that public transportation is more sustainable in all impact categories compared with private automobiles. Most importantly, public transportation is key for addressing the critical environmental impacts of the transportation sector: climate change, particulate matter formation, human toxicity, terrestrial acidification, and water depletion. Annually, a public transportation metro line can reduce approximately 19.42 kt of CO2 emissions, 3.15 tonnes of PM 10 formation, 377.17 tonnes of 1,4-dichlorobenzene, 3.02 tonnes of nitrogen, 11.45 tonnes of sulfur dioxide, and 1.5 cubic meters of water. Electricity and water are the primary factors for the environmental impacts of the metro system; consequently, their impact can be further mitigated using cleaner renewable energy sources and through creation of strategic solutions to increase the use of the metro transit system.