air quality: Higher speeds have the potential to discourage walking and cycling leading to increased reliance on private motor vehicles (in turn leading to pollution and poor air quality).
ansawdd aer: Gall cyflymderau uwch atal pobl rhag cerdded a beicio gan arwain at fwy o ddibyniaeth ar gerbydau modur preifat (sydd, yn ei dro, yn arwain at lygredd ac ansawdd aer gwael)