Public transportation, an enduring hallmark of urban landscapes worldwide, assumes a pivotal role in the mission to abate carbon emissions and foster sustainable urban mobility. The scale at which public transit operates renders it a formidable instrument in the pursuit of environmental sustainability. Opting for mass transit systems—comprising buses, subways, trams, and commuter rail—over personal vehicles underscores a profound contribution to the reduction of greenhouse gas emissions.

Intrinsically, public transit holds the promise of reducing urban carbon emissions significantly. Our analysis underscores that it accounts for 29 to 34 percent of total urban passenger journeys, thus having the potential to mitigate emissions equivalent to 9.42 – 15.42 gigatons of carbon dioxide. This commendable reduction in emissions also translates into considerable economic benefits for consumers, estimated at approximately US$3.7–5.9 trillion in terms of mobility expenses.

Public transit not only delivers environmental advantages but also alleviates congestion on city roads, reducing accident rates and fatalities. It plays a pivotal role in curbing air pollution, offering equitable mobility solutions to individuals who lack access to private automobiles. With the urban population poised for significant growth from 2023 to 2050, public transit stands ready to meet the surge in travel demand while conferring a host of additional societal benefits.

The Public transit solution, as envisioned by Project Drawdown, champions the extensive utilization of urban mass transit systems for passenger transportation. This encompassing concept includes metro systems, trams, light-rail transit, buses, bus rapid transit, and minivans. The focus is to inspire passengers to prefer mass transit more frequently, without the consideration of infrastructure expansion or the public investments that may be necessary to accommodate this increased demand. Ultimately, this solution supersedes the reliance on traditional internal combustion engine (ICE) vehicles.

Our calculations are rooted in the total addressable market for public transit, which encompasses the entirety of urban mobility, measured in passenger-kilometers, as foreseen by reputable institutions such as the International Energy Agency (IEA 2023), the International Council on Clean Transportation's decarbonization analysis (ICCT), and collaborative research efforts by the Institute for Transportation and Development Policy and the University of California–Davis (ITDP/UCD).

It is crucial to acknowledge that traditional ICE vehicles still dominate the market share in affluent regions, including Europe and North America, while public transit adoption in low-income countries confronts challenges posed by economic growth trends that often shift demand towards private vehicle ownership.

Our analysis of the potential impacts of enhanced public transit adoption from 2020 to 2050 assumes informed decisions by stakeholders and policymakers to promote global public transit utilization, with a target of reaching 29 percent of urban passenger kilometers by 2050.

Our financial analysis adopts a user-centric approach, focusing on the perspective of individual travelers. By comparing the costs associated with using public transit against internal combustion engine (ICE) vehicles, we deliberately exclude initial implementation costs to prevent misinterpretation. This approach is rooted in net operating costs, encompassing factors such as weighted average ticket prices for public transit options and fixed operating expenses, including insurance, depreciation, fuel costs, and other ownership-related expenses for private vehicles.

In this scenario, we foresee a reduction of 9.42 gigatons of carbon dioxide equivalent greenhouse gases and the generation of a lifetime net operational savings totaling US$3.6 trillion.

Without targeted public transit investments and policies, urban mobility growth is poised to be dominated by ICE cars, even with innovations such as electric, autonomous, and shared vehicle fleets. Therefore, the urgency of making public transit an appealing mode of urban transportation in our increasingly urbanized world cannot be overstated. While our analysis did not factor in government investment costs for public transit, it also did not consider the ancillary benefits of reduced private vehicle congestion and the potential reclamation of city space from unnecessary parking lots. Nevertheless, it is improbable that including these aspects would alter the fundamental conclusion that public transit is indispensable in reducing urban transport emissions.

References.
World Atlas. https://www.worldatlas.com/articles/cost-of-public-transportation-around-the-world.html.
The International Council on Clean Transportation. https://theicct.org/pv-fuel-economy/.