Impact of vehicular exhaust emissions on pedestrian health under different traffic structures and wind speeds

To explore the effects of different traffic structures and wind speeds on concentration distribution of multi-component pollutants, CO, C4H8, and NO2 with proportions of 81%, 12%, and 7%, respectively, were selected for computational fluid dynamics simulations. Their concentrations were estimated in a reference scenario and five contrast scenarios. When the number of cars is reduced by 15%, their concentrations at point 1 (-28, 1.5) and point 2 (28, 1.5) will decrease by more than 10%. When the number of cars is reduced by 25%, their concentrations will decrease by 20%. The largest concentration in 1.5 m above the ground level under six scenarios is measured on the leeward side when x=-3.3 m. Even if the wind speed increases to 3.0 m/s, the position where the largest concentration occurs remains the same. When wind speed increased to 3.0 m/s, the pollutants concentration on the leeward side decreased by an average of 4%, whereas that on the windward side decreased by an average of 11%. An additional 3.2%, 3.4%, 3.4%, 2.8%, 3.3%, and 3.1% reduction in CO concentration on the leeward side occurred. These results can help to strengthen the policy-making to create a good travel environment for pedestrians.