# Evaluation of Turkey's Road-Based Greenhouse Gas Inventory and Future Projections
###### Abstract
Air transportation accounts for 2.7% of emissions, maritime contributes 1.6%, railway contributes 0.4%, and other transport modes contribute 0.4% [12]. Transport emissions encompass not only carbon dioxide (CO\({}_{2}\)) and methane (CH\({}_{4}\)), which are the primary contributors to climate change, but also additional pollutants, such as particulate matter (PM), sulfur dioxide (SO\({}_{2}\)), and nitrogen oxides (NO\({}_{\rm X}\)) [13; 14]. Transportation plays a crucial role in sustainable development, as it relies heavily on fossil fuels and significantly contributes to carbon emissions, one of the leading GHGs. Furthermore, the transportation industry contributes to other adverse consequences, such as soil erosion, traffic congestion, air pollution, and ecosystem destruction. Hence, it is of the utmost importance to develop and execute sustainable transportation strategies. The first step is to identify the existing conditions. Once the situation is assessed, the subsequent stage involves making future projections and establishing the necessary goals and strategies. Since road traffic in Turkey is a significant source of emissions due to the increasing number of vehicles on the road, the goal of this study was to conduct an inventory and calculate the emissions of direct GHGs, namely CO\({}_{2}\) and nitrous oxide (N\({}_{2}\)O). It also aimed to assess pollutants that indirectly contribute to climate change, such as ammonia (NH\({}_{3}\)), NO\({}_{\rm X}\), SO\({}_{2}\), CO, NMVOC, and PM, from vehicles traveling on the state roads of Turkey between 2010 and 2020. At the same time, the purpose was to conduct a precise analysis of present emission levels and estimate future emissions (up to 2050). When the accessible literature was surveyed, studies were found that analyzed traffic-related emissions for some cities and made recommendations for reducing emissions [15; 16; 17; 18; 19; 20; 21; 22; 23; 24]. For instance, [PERSON] and [PERSON] (2020) modeled GHG emissions from Istanbul's transport system using scenario analysis, projecting to the year 2050, while [PERSON] and [PERSON] (2018) examined carbon footprint variations resulting from transportation activity in selected regions [18; 20]. Similarly, [PERSON] et al. (2009) conducted a long-term emission reduction analysis in California, emphasizing policy scenarios rather than inventory-based modeling [24]. However, when the impact of GHGs is particularly significant, it has been observed that the assessment of GHG emissions from vehicles on all state roads, excluding major cities, has not been adequately conducted. The present research develops a comprehensive, province-level GHG emission inventory for all state roads in Turkey for the period 2010-2020, employing official traffic data and EMEP/EEA Tier 1 emission factors. Furthermore, it applies polynomial regression techniques using 55 years of vehicle registration data to forecast future emission trends up to the year 2050. Emissions are also spatially visualized through GIS (Quantum GIS- QGIS Development Team-Version 3.10) mapping, offering detailed insights into the distribution of pollutants across provinces. As a result, the study's goals are unique; it will highlight rising emission levels and make significant contributions to other studies focusing on similar topics. Publishing these and similar findings and disseminating them to different audiences--including policymakers--will also serve as a crucial roadmap for decision-making regarding emission reduction.