All roads are well sign posted, were not that backwards
built up areas vary from 50-60kmh
Equivalent dual-carriage ways are 70-90kmh
Freeways/State Highways 100-110kmh
As for fines as long as you go no more than 10kmh over your only looking at a $75 fine.
Dont drive like an arse and the cops general leave you alone, cameras are random and mobile, not fixed like back in the UK, only red light cameras are fixed here.
A list of all mobile locations where speed cameras are placed are published a week in advance on the state police website (
http://www.police.wa.gov.au/ABOUTUS/...0/Default.aspx)