Cyflwynwyd y terfynau cyflymder ym mhob un o'r lleoliadau ar ôl i ymchwil ddangos y potensial i wneud gwelliannau i ansawdd aer ar unwaith, mewn ffordd sy'n lleihau cysylltiad â nitrogen deuocsid cyn gynted ag y bo modd, ac sy’n golygu bod sicrhau cydymffurfedd nid yn unig yn bosibl ond yn debygol.
The speed limits were introduced at each of the locations as research demonstrated the potential to bring immediate improvements to air quality, and bring forward compliance which would do in a way that reduces human exposure to NO2 as quickly as possible and will mean that achieving compliance is not just possible but likely.