Torfaen, Isle of Anglesey, Blaenau Gwent and Merthyr Tydfil had the lowest volumes of motor vehicle traffic and their combined volume represented just 7% of total traffic in Wales.
Gwelwyd y lefelau isaf o draffig cerbydau modur yng Ngheredigion, ar Ynys Môn, ym Mlaenau Gwent a Merthyr Tudful.