What specific environmental problem does designing cities around public transit aim to reduce by lowering car use?

Designing cities around public transit primarily aims to reduce atmospheric pollution, which encompasses both the degradation of local and regional air quality and global climate change. This specific environmental problem stems from the combustion of fossil fuels—such as gasoline and diesel—in the internal combustion engines of private vehicles. When these fuels burn, they release a variety of substances into the atmosphere. One major group consists of greenhouse gases (GHGs), predominantly carbon dioxide (CO2), but also methane (CH4) and nitrous oxide (N2O). T....