The M4 Motorway (Junction 40 (Tai Bach) to Junction 42 (Earlswood), Neath Port Talbot) (50 mph Speed Limit) Regulations 2019 / Rheoliadau Traffordd yr M4 (Cyffordd 40 (Tai-bach) i Gyffordd 42 (Earlswood), Castell-nedd Port Talbot) (Terfyn Cyflymder 50 mya