[Note 2] The year 1998-99 was chosen as the base year as that was the low-point in bus travel for Great Britain as a whole.
[Nodyn 2] Cafodd y flwyddyn 1998-99 ei dewis fel y flwyddyn sylfaen gan fod teithiau ar fysiau ar y lefel isaf ar gyfer Prydain Fawr gyfan yn y flwyddyn honno.