These data are derived from annual returns made to the Department for Transport (DfT) by a sample of 700 holders of Public Service Vehicle operators’ licences (‘the PSV survey’).
Mae’r data hyn yn deillio o ddatganiadau blynyddol a wnaed i’r Adran Drafnidiaeth gan sampl o 700 o ddeiliaid trwyddedau gweithredwyr Cerbydau Gwasanaeth Cyhoeddus (‘yr arolwg PSV’).