Here,
"If your folding bicycle has small wheels and is in a bag no more than 86 cm long, 68 cm high and 36cm wide, you may carry it on any bus, train or ferry service. Please consider your fellow passengers by keeping your folding bike out of aisles and off seats that others need."

More info-
https://www.transperth.wa.gov.au/usi...board/bicycles