The objective of street canyon ventilation control in major streets is a tool of air pollution prevention in them, protection of housing areas from excessive wind or preservation and intensification of existing wind speed in case of insufficient ventilation. The maximum permissible concentration of car exhaust pollutants with wind speed within comfortable and permissible values by physiological and hygienic criteria, are ensured as from 40 to 70 % of thoroughfares in major cities. The dependence of air pollution level on wind speed is comparable to its dependence on traffic intensity and ratio of buildings height (H) to street width. But one has to take into account that, if the wind blows across the street, vortices form within the street canyon, which results in higher concentration of car exhaust pollutants near the downwind buildings. The objective of this work is to find the functional dependences of wind speed in a major street on its width and density of buildings, and also to find out which street configurations are favorable for formation of closed air circulation within it, resulting in insufficient aeration. The experimental research was done on a site for large-scale modeling of built-up urban territory, using cup anemometers. The coefficients of dependence of wind speed within a street on the types of buildings and on the street width were obtained. Characteristics of street layouts for control of aeration were determined. Building density rates for maximizing or optimizing the wind speed were determined. Street layouts are considered where stable vortices form between the buildings. For example, vortices within the street canyon’s cross-section appear when buildings squarish in ground plan situated far apart are replaced by oblong ones with the minimum allowed intervals of 15 meters between them (for 5-storeyed buildings; or intervals equal to the buildings’ height), or where the buildings are long and close together. With separate buildings of reasonable length and sufficient intervals between them, and with street width over 9 H… 10 H , the buildings’ influence on wind speed lessens, and the vortices do not form between buildings. Thus the danger of excess air pollution within street canyon is eliminated. On the other hand, the air flow over the trafficway slows down more at the intervals between the buildings than at their mid-lengths, and this effect is more prominent when the buildings are narrow in the direction along the street (like 10…25 meters). This could be explained by forming, and gradual increasing in number, of small chaotic vortices with conflicting directions, even counter-directional, at the corners of buildings as the intervals between buildings increase in number. In real life, in order to protect the streets from strong winds, it is advisable to use certain planning methods, like alternate side-shifting or rotating the buildings in the row, additional space between them and the trafficway, alternating buildings of different height, and other non-linear plan and height configurations. At the same time, they should ensure lesser concentrations of toxic air pollutants within the streets, and the intervals between the buildings should be at least corresponding to the sunlight norms and fire regulations.