## 3 Description of the Research Methodology
### Characteristics of the Experimental Sections of the Streets and the Equipment Used  
When measuring the cars' speed by the method of a stationary measuring site, the first stage is the selection of a section of the road that meets the specified requirements. Since free traffic is subject to a number of mandatory conditions that exclude the influence of other road users on the driver's speed decision, the range of suitable sections of the city road network for measuring FFS is quite limited. When measuring FFS, outliers of values in the low-speed range can occur when the driver has just entered the road or has resumed driving in front of the measuring station or is about to make a turn or stop a short distance from it. Therefore, the location of the measuring post should be remote from road intersections and pedestrian crossings, parking lots, and places with traffic lights. Then, the driver will maintain the selected speed throughout the entire section of the street with stable road conditions. Streets in the downtown area may not meet conditions due to high traffic volumes where free-flowing conditions may occur during limited periods of the day, primarily at night or early morning. Random factors such as weather conditions, obstacles, or road surface defects will also be able to contribute to the measurement results. In order to check the effectiveness of the chosen methodology and obtain experimental distributions of FFS on the street and road network of the city of Kharkiv, four sections were selected, where measuring sites were located. The street sections were divided into two groups according to their functional class. This division is contained in the state standard of Ukraine (B.J.H.B.2.3-5) [30]. \"Main streets\" provide traffic in major directions and transportation connections between different parts of the city. \"Local streets\" provide transportation connections between adjacent areas of the city and between arterial streets. Street sections were also divided according to the traffic management feature (one-way or two-way traffic). Two sites were located on sections of city-wide main streets (Ave. Heroiv Kharkova and Ave. Traktorobudivnykiv), and two sites were located on sections of local streets (St. 12-ho Kvitnia and St. Myru). Sections on Ave. Heroiv Kharkova and St. 12-ho Kvitnia had one-way traffic, sections along Ave. Traktorobodivnykiv and St. Myru had two-way traffic. The selected sections did not have longitudinal slopes and curves, and the measuring sites were at least 300 m away from the nearest intersection. The sections had an asphalt concrete surface without defects that would affect the speed of vehicles. On all streets, the roadway had a raised curb. Brief characteristics of road conditions at the sites are given in Table 1. Figure 1 shows the location of the measuring sites on the city map. Bushnell II Speed Radar Gun 101911 (Overland Park, KS, USA) was used for measurement. The radar allows you to easily measure the speed of the car with a measurement accuracy of \(\pm 1\) km/h. The radar of this brand uses DSP (Digital Signal Processing) digital technology to ensure accurate measurement in real time.