Vu D. Improvement of traffic management efficiency in transport zones of a city

The dissertation is devoted to the solution of the applied scientific problem of the estimation of the influence of complicated traffic conditions on vehicle speed and determination of the distribution of the vehicle speed on urban street networks. The analysis allowed defining that most of the existing approaches to predict vehicle speed implies determining its average value at some point or a short road section in any traffic conditions. It points to the need for the study of vehicle speed in a city as the random variable and, correspondingly, the de-termination of its distribution law. To adequately represent the speed of traffic flows between the transport attractors located along the streets in the city centres, a new approach to traffic assignment based on vehicle delays at intersections was developed. At the same time, the comparison of alternative traffic assignment methods with the use of the real transport models provided the possibility to compare calculated traffic volumes with actual ones and brought the scientific problem under the study close to the problems arising in model-ling practice. Further study made it possible to define that under the most difficult driving conditions, normal vehicle speed distribution changes to an exponential one. The gamma distribution was used as a connecting link in the transformation of the normal distribution into an exponential one under traffic conditions complication since the exponential distribution is the special case of gamma distribution with the shape parameter equal to 1, and the normal distribution is the limiting case of gamma distribution with the shape parameter tending to infinity. Experimental confirmation of the possibility to use the gamma distribution to describe the speed variable was received when studying the car speed influenced by the narrow carriageway and by the zone of influence of signalized intersection. The data about vehicle speed in urban areas in different countries collected during the research made it possible to obtain the regression model reflecting the relationship between the average speed and the shape parameter of the gamma distribution suitable for describing the regularities in speed values. The obtained model has sufficient predictive capability since the multiple correlation coefficient equals 96.3%. Based on the research results, practical recommendations to apply defined regularities in the variable of private transport speed in cities were developed. The developed recommendations and methods were applied during traffic flows modelling for the Long Biên district in Hanoi city and assessing the road network performance under different traffic conditions. Two options of traffic management in the district were considered – the current network state and the state with the rational traffic signal cycles at all signalized intersections in the district. These changes relate to the most loaded part of the road network as well as make it possible to evaluate the practicability of the developed methods and the effectiveness of the proposed recommendations. If the proposed traffic signal cycles are used, then total vehicle delays at signalized intersections in the Long Bien district should decrease by 12.47%, the average vehicle speed between transport attractors should increase by 0.55%, exhaust emissions should decrease by 0.56%, acceleration noise should decrease by 5.88%. It confirms the feasibility of the use of new methods for a comprehensive assessment of urban transport networks performance.