Winds in Cities: Effects on Pedestrians and the Dispersion of Ground Level Pollutants

Abstract

Individual buildings or groups of buildings obstruct the flow field and tend to create locally sheltered, as well as windier areas. Windy conditions near ground in built-up city areas have in some situations raised concerns for both the comfort and the safety of pedestrians. As a result the assurance of an acceptable pedestrian level wind environment has become an important consideration in the design of new buildings. This has lead to the development of special wind tunnel modelling techniques which can provide reliable measures of winds at pedestrian level; special procedures which can combine the wind tunnel model data with the local wind climate to provide predictions of the likely occurrence of certain wind conditions; and criteria for judging their acceptability. The latter have been difficult as acceptability criteria not only involve considerations of physical safety but also address human comfort. The latter is highly subjective and includes other elements of the weather such as the air temperature, the presence of sunshine, relative humidity and precipitation. A significant body of information on pedestrian level winds is now available in the literature (Refs. 1 to 9).