## 1 Introduction
To understand the true impacts of emissions, it is crucial to comprehend how goods and services are consumed by society and measure the resulting effects. Inventories are conducted to assess the environmental impact of activities known to be polluting and environmentally harmful, emitting high levels of CO\({}_{2}\) and greenhouse gases (GHGs), and generating solid waste. These inventories employ tools such as life cycle assessment to provide a more precise understanding [11; 24; 25]. The methodology of life cycle assessment (LCA) has been employed in several transport studies, applied to different transport modes such as road [25; 26], rail [24; 27], maritime [28], inland waterways [29], and air transport [30]. Globally, researchers have conducted varied studies from a life cycle perspective in the field of rail transport, with the aim of measuring the main sources of environmental impacts, emissions, and costs. One study developed a comprehensive component-based life cycle assessment model in France [6], with clear and reusable life cycle inventories (LCIs) for high-speed rail (HSR) infrastructure components. Life cycle analysis (LCA) is used for the identification and quantification of material, energy, and emissions across all stages of the system and enables the identification of appropriate mitigation measures [10]. An LCA of a light rail trip would include the direct effects (moving the train), ancillary effects (e.g., evaluating the total greenhouse gas emissions from constructing the infrastructure and dividing it by the total number of trips), and supply chain effects (e.g., evaluating the greenhouse gas emissions from mining materials for train manufacturing and dividing it by the total number of trips served in the train's lifetime) [31; 32]. Policymakers should take into consideration how policies might affect overall vehicle miles traveled, the number of vehicles on the road (i.e., traffic congestion), the availability and utilization of alternative modes of transport, and possible solutions to enhance the environmental benefits and mitigate the potential economic implications of a policy. In light of all the facts mentioned, mapping the GHG emissions of the railway system in Pernambuco, Brazil, will aid the region in managing the environmental impacts of public transportation while improving environmental sustainability and aligning with state development goals. Through economically characterizing activities associated with increased mobility and reduced environmental impact, it becomes possible to understand the process of sustainable development within the public transport system, considering local peculiarities and potentialities. This understanding will guide the design of measures and public policies to address national environmental concerns [33; 34; 35]. Furthermore, this study will contribute to the theoretical and methodological framework concerning the environmental impacts of public transport activities and the development of public policies for railway infrastructure. The field of environmental impact and sustainability in the railway system remains largely unexplored, despite mechanical engineering, engines, fuels, maintenance, and urban train transportation planning being the main research areas within global railway research [27]. It highlights the need for further research in this area. Considering interdisciplinarity as a guiding principle, this research project aims to explore the atmospheric impacts of the railway system. Its ultimate purpose is to conduct a greenhouse gas emissions inventory of the railway system in Pernambuco, Brazil, comparing it with other national railway systems, and proposing mitigation models to reduce this environmental impact. In this way, the study aims to provide strategic data for policymakers, urban planners, and other stakeholders, with the goal of promoting improvements in the railway system, mitigating air pollution, and enhancing the quality of life for future generations.