The conclusions are also consistent with research into the wider economic effects of improving the A40 in West Wales carried out by Berkeley Hanover Consulting for the Transport Directorate.
Mae'r casgliadau hefyd yn cyd-fynd â'r ymchwil a wnaed gan Berkeley Hanover Consulting ar gyfer y Gyfarwyddiaeth Drafnidiaeth i effeithiau economaidd ehangach gwella'r A40 yng Ngorllewin Cymru.