But several initiatives are possible in established urban areas. Amelioration of the urban-heat-island effect in summer can be aided by the provision of trees for de, sprinkling the streets to i evaporative cooling, and increasing the albedo by employing light-coloured paint on roofs and the replacement of open parking lots by garages. The utility of vegetation to improve urban climates is also widely acknowledged. As well as increasing cooling in summer by evapo-transpiration, trees and other plants reduce run-off and, if judiciously planted, will reduce particulate concentrations and noise pollution. Some of the undesirable wind eddies created by the tall buildings of the urban canyons can be avoided by sympathetic planning of street widths and orientations, and by employing appropriate building design. In cities where snow and ice are common winter problems, the channel- ling of heat under footpaths and streets, at waste least at critical points in the urban traffic system (such as bridges, slopes and pedestrian crossings.