Page "Caerleon" Paragraph 30

Conversely, traffic joining the M4 from Caerleon can join the M4 eastbound at Junction 25 but to join the M4 westbound traffic must follow the Junction 25A offslip, Heidenheim Drive, Malpas Road route to M4 Junction 26.

Alternatively, traffic can join the M4 both eastbound and westbound at Junction 24.