Areas where vehicles, including cars, motorcycles and vans, need to meet ultra-low emissions standards or they have to pay a charge to drive within the zone.
Ardaloedd lle mae angen i gerbydau, gan gynnwys ceir, beiciau modur a faniau, fodloni safonau allyriadau isel iawn neu mae'n rhaid iddynt dalu i yrru o fewn y parth.