# Evaluation of Turkey's Road-Based Greenhouse Gas Inventory and Future Projections
## 4 Conclusions  
The present study revealed a significant and rapid increase in vehicle numbers on Turkey's roads between 2010 and 2020. Although growing alternative transportation networks have yielded benefits, the increased number of vehicles in the transportation sector has led to a rise in fossil fuel use and, consequently, greenhouse gas emissions. Unless the proportion of fossil fuels in the global energy mix declines, these emissions will continue to rise.  
Automobiles are responsible for about half of all vehicle-related pollutants. However, diesel fuel used in HDVs is accountable for a considerable part of CO\({}_{2}\) emissions, a significant greenhouse gas. This situation demonstrates the need for improvements in the use of diesel fuel.  
When the calculated emission quantities by province were studied, Ankara, Antalya, and Bursa were determined to be the three cities with the highest emissions, despite several variances. The Kocaeli and Yalova provinces were rated as having the highest GHG emissions per square kilometer, whereas the Bilecik province was determined to have the most significant GHG emissions per person. The increase in emissions was a result of urbanization and the increasing number of vehicles. Therefore, governments are advised to develop strategies to reduce emissions from transportation, particularly targeting large cities.  
According to the future forecast study, a 105% rise in the number of registered automobiles is projected by 2050. This logically implies that if the advances, initiatives, and policies enacted between 2010 and 2020 continue in the same manner, and no measures are taken, emissions will rise by more than 100%.  
It is essential to highlight that energy consumption contributes to the rise in specific GHG emissions, specifically CO\({}_{2}\). To keep GHG emissions as low as possible, reduce pollutant emissions, and meet the 2053 net zero target, it is critical to develop transportation transformation targets that are aligned with global emission reduction strategies, ensure a shift to more sustainable railway/maritime transportation, increase efficiency and clean energy use in transportation strategies, and keep up with new technological developments. Furthermore, higher environmental standards and regulations must be implemented to lessen the link between transportation frequency and greenhouse gas emissions.  
For future research, it is recommended to develop scenarios that explore how different numbers of vehicles and fuel types on roadways might reduce greenhouse gas emissions in the transportation sector. Incorporating spatial regression techniques, such as Geographically Weighted Regression (GWR), can effectively address spatial autocorrelation in emission models, thereby enhancing the interpretability and accuracy of GIS-based analyses.  
Limitations of the study: This study is limited to state roads, which constitute only 45.4% of the total roads. Provincial roads comprise 50.1% of the total. Nevertheless, they were excluded since there are no vehicle statistics for these roads. Similarly, motorways, which account for 5% of the total, were excluded because of their low proportion. However, the motorways are very heavily used, so when considering the emissions generated by traffic on these motorways, it would be reasonable to say that the amount of emissions from all types of road transportation in Turkey is higher than those calculated in this study. There are three approaches (tiers) for emission estimations. The Tier 2 and Tier 3 approaches provide more accurate results because they require more detailed information than Tier 1. However, it is difficult to obtain detailed data for the entire country. Therefore, calculations were performed using the Tier 1 approach in this study. This situation is seen as a study limitation, even though it is acceptable for macro-level analysis.