EXPERIMENTAL STUDY OF TRANSPORT FLOWS IN BIG CITIES.

In the present work a methodology has been developed to study some parameters of traffic in characteristic sections of urban infrastructure. For this purpose, the average driving speeds, average fuel consumption and their impact on environmental performance are determined. The traffic in the road infrastructure of the capital of Bulgaria - Sofia has been studied. In the study, the road infrastructure is divided according to the degree of traffic load into three main groups. These are transport sections in the center of the city with high traffic during heavy traffic hours, sections with medium load and sections of highway type. An experimental study was performed for the three types of sections. For these sections the speeds of movement in typical time zones, fuel consumption, the speed of the car's exhaust gases and ecological indicators were measured. The work introduced a coefficient of stay, reflecting the ratio of the time in which the car was moving at a speed below 1 km⋅h-1 or was at the traffic lights to the total travel time in the section. This coefficient is introduced to determine the traffic load in the respective sections. The study of the speed of cars in these sections is also important in the case when conventional cars are replaced by those that use electricity (electric cars). The test performed to measure the exhaust gas flow rate depends on the engine operating modes. The speed of the exhaust gas discharge has a direct impact on the environment. The speed of the gases is different in the different speed regimes of the car. The percentage of the various components in the exhaust gases and the knowledge of the outflow rate make it possible to determine the volumes or quantities of harmful emissions emitted into the atmosphere. The developed methodology and the performed research can be used for assessment of the transport network in busy urban areas, correction of the results obtained by WLTP or NEDS and prognosis. The dimensionless coefficient is introduced in the work for the first time. It is the ratio of the time in which the car is at rest (speed below 1 km⋅h-1) to the total time for passing the relevant section. The coefficient reaches the road sections loaded in certain time zones to values 0.40-0.45. Another indicator that is being introduced for the first time is the volume of exhaust gases. [ABSTRACT FROM AUTHOR]