Mae Porterbrook hefyd wedi cytuno i roi trenau ychwanegol i Trafnidiaeth Cymru tan i'r trenau a archebwyd yn flaenorol, y Class 769 fod ar gael i'w defnyddio. Mae Trafnidiaeth Cymru eisoes wedi cadarnhau bod fflyd fodern yn cyrraedd yn gynt (o'r enw Class 170), fydd yn darparu rhwng 118 a 181 o seddau yr un. Bydd y rhain nid yn unig yn rhoi capasiti ychwanegol, ond gwell hygyrchedd, pwyntiau gwefru ac aerdymheru. Ar y dechrau, bydd y trenau hyn yn gwasanaethu teithwyr rhwng Cheltenham, Caerdydd a Maesteg, a rhwng Caerdydd a Glyn Ebwy.
Porterbrook have also agreed to provide TfW with additional trains until the previously ordered Class 769s are available for use. TfW has already confirmed the earlier delivery of a modern fleet (known as Class 170), which will each provide between 118 and 181 seats. These will provide not only additional capacity, but, also, improved accessibility, charging points and air conditioning. Initially, these trains will serve passengers between Cheltenham, Cardiff and Maesteg, and between Cardiff and Ebbw Vale.