The improvements will be carried out primarily at night until February 2018, with the M4 scheduled to be closed between junctions 25A and 26 from 8pm to 6am on up to five nights per week.
Bydd y rhan o’r M4 rhwng cyffyrdd 25A a 26 ar gael rhwng 8 y nos a 6 y bore am hyd at 5 noson yr wythnos.