O heddiw ymlaen, mae Llywodraeth Cymru wedi rhybuddio y gallai modurwyr sy'n gyrru’n gyflymach na'r terfynau cyflymder o 50mya rhwng cyffyrdd 24 a 28 ar yr M4 gael dirwy.
From today, motorists exceeding the 50mph speed limits between junctions 24 to 28 on the M4 could be fined, the Welsh Government has warned.