## 7 Conclusions
When interpreting the results and conclusions of the research conducted within this paper, it is necessary to consider the following methodological and spatio-temporal limitations and research constraints:  
* The empirical samples used in this research to identify representative deterministic \"speed-density\" and \"flow-density\" models were gathered over relatively short periods and exclusively on the two representative road segments of ZC5210 regional road. All of the models considered were fitted to an empirical sample, which did not include the empirical traffic flow parameter values measured in a congested traffic flow condition, i.e., at traffic flow densities higher than 93.00 veh/km. * Twelve traffic flow models selected were fitted directly to disaggregated empirical data collected on the two observed road sections of regional road ZC5210 in the Republic of Croatia. The impacts of higher levels of time aggregation of the observed traffic flow parameter empirical values on the shape of regression functions used to describe the relations between average traffic flow parameter values were not considered in this research. * The impact of traffic flow structure, road environment characteristics, relevant road design and road infrastructure elements on the shapes of the obtained \"speed-density\" and \"flow-density\" regression functions was not considered in the scope of this research. Based on the obtained results, derived conclusions and defined limitations of the research performed, the following suggestions and guidelines for future research are proposed:  
* Future research should prioritize the collection of extensive statistical sample with a sufficient number of empirical values of traffic flow parameters measured in a congested traffic flow condition. Based on such sample, it would be possible to further examine the possibility of developing other specific non-linear regression models, which would enable more accurate descriptions of the mathematical relationship between average speed and density values under high-density (unstable) traffic flow conditions. * In future research, it is also important to investigate the impact of higher levels of time aggregation of the observed traffic flow parameters, as well as the impact of traffic flow structure, road environment characteristics, relevant road design and infrastructure elements and other relevant factors, which possibly contribute to the scattering effect of empirical data visible in the \"speed-density\" and \"flow-density\" fundamental diagrams. The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app14020533/s1](https://www.mdpi.com/article/10.3390/app14020533/s1)]([https://www.mdpi.com/article/10.3390/app14020533/s1](https://www.mdpi.com/article/10.3390/app14020533/s1)), Table S1: ZC5210_Road_Section_A; Table S2: ZC5210_Road_Section_B; and Table S3: ZC5210_Comparative_Models. Tables S1 and S2 contain the input data used to perform the correlation and regression analysis and to develop the \"speed-density\" and \"flow-density\" models representative of continuous and interrupted traffic stream conditions,which were obtained based on the processing and analysis of aerial video files recorded using an unmanned aerial vehicle on two selected road segments of \(\mathbb{Z}\)C5210 regional road in the Republic of Croatia. The tables include data on vehicle ID numbers, vehicle types, lengths of observed road segments and data on the empirical values of traffic density, time headways, vehicle speeds and vehicle flows, determined on the open road segment (Road Section A) and the road segment with signalized intersection (Road Section B) of the selected regional road. Table S3 contains the cumulative empirical sample of traffic flow parameter values collected on both observed road segments, together with the data on traffic flow parameter values, determined based on the developed \"speed-density\" and \"flow-density\" models. Conceptualization, B.J., M.S. and G.L. ; methodology, B.J. ; validation, B.J., M.S.