Still ED related to roadside vegetation must be considered.
Trees or dense shrub layers can reduce wind speed and nearsurface
air exchange in narrow streets and thereby increase local
air pollution (Buccolieri et al., 2009; Salim et al., 2011; Vos et al.,
2013). Hence, greening initiatives that only aim to increase street
tree coverage can be misleading (Pugh et al., 2012). The challenge
thus is to use both trees and herbaceous vegetation, optimized to
local conditions.