Separate, smaller surveys managed by DfT collect information about fare changes, service reliability and quarterly patronage from the larger bus operators.
Mae arolygon llai, ar wahân sy’n cael eu rheoli gan yr Adran Drafnidiaeth yn casglu gwybodaeth am newidiadau mewn prisiau, dibynadwyedd y gwasanaeth a nawddogaeth chwarterol gan y cwmnïau bysiau mwy.