Mae allyriadau nitrogen deuocsid wedi gostwng ym mhob lleoliad ar y rhwydwaith traffyrdd a chefnffyrdd lle y cafodd terfynau cyflymder o 50mya eu cyflwyno, yn ôl adroddiad newydd.
Emissions of nitrogen dioxide (NO2) have reduced at all 5 locations on the motorway and trunk road network where 50mph speed limits were introduced, a new report has shown.