Electronic “beeper” or etags are currently used on all major Australian toll roads, including Melbourne’s City Link and Queensland’s Logan and Gateway motorways.
In Sydney the road network includes the Sydney Harbour Bridge and Tunnel, Cross City Tunnel, Lane Cove tunnel, M1 Eastern Distributor, M2 Hills Motorway, M4 Western Motorway, and M5 South Western Motorway and the M7 ringroad
The tag is a small device attached to the front windscreen of the vehicle. As the vehicle passes one of the tolling points of the tunnel, the tag will transmit a signal to the tolling equipment. This will acknowledge and deduct the appropriate toll amount from your toll account.
There are several different beep tags you can sign up for around the country and Motorists can use any of them on all Australian toll roads.
The NSW RTA E-tag is probably the best e-tag to get as it has no fees at all (other than the cost of a toll) and no stupid fees for tag inactivity plus you get statements posted every quarter for free.
Another good option from Queensland Motorways is an E-toll tag that seems to be the good value for people living out of town and only doing occasional trips to cities. There is no joining fee, no inactivity fee, minimum initial payment $25 and then top ups when you get down to $15 to be made in multiples of $25.
Two alternatives im aware of are the “Beep Tag” system setup by Sydney’s Cross City Tunnel, and the E-way™ tag powered by the consortium that runs Sydney’s M5 & M4 motorways as well as the Eastern Distributor