The work will also look at options for doubling the bus service frequency between Caernarfon and Porthmadog, to improve connectivity to rail links to South and Mid-Wales.
Bydd y gwaith hefyd yn edrych ar opsiynau ar gyfer dyblu amlder y gwasanaeth bws rhwng Caernarfon a Phorthmadog, er mwyn gwella cysylltedd â chysylltiadau rheilffordd â De a Chanolbarth Cymru.