Five years after it first said it wanted to introduce cashless tolling on the M2, the road's owner, Transurban, has agreed with the government to scrap toll booths during the current road-widening project.

The Roads Minister, Duncan Gay, said the government would look to bring in cashless tolling on the M5 and the Eastern Distributor, but would have to negotiate with the road's owners.

''Once we do this one they're the next ones on our agenda,'' Mr Gay said.

The minister also said he would be open to changing the toll structure on the Harbour Bridge, where motorists are charged a premium during peak hours.

''I believe that if you have no alternative, it is like congestion charging, it is an unfair toll,'' he said. ''If someone's got an idea to make that fairer, but still return the same sort of money, I would be happy to look at it.''

Announcing the shift to cashless tolling on the M2, the acting NSW Premier, Andrew Stoner, said: ''The days of fumbling for coins in your car ashtray are over.''

''For motorists from the north-west it will be a quick trip straight through, no merging of lanes, 100km/h all the way through,'' Mr Stoner said.

Mr Gay admitted that shifting to cashless tolling was a relatively minor reform, though he questioned why the previous Labor government did not introduce it.

But the minister did hold out the promise of some significant changes to road pricing.

Asked if he would consider ways of lowering tolls on the M2 during the upgrade program, which has made congestion worse on the artery, Mr Gay said he had asked the Roads and Traffic Authority for a report into the options available to him.

''The issue of a reduced toll during construction certainly is one that we have asked about and it is … certainly one that I would be willing to look at,'' Mr Gay said.

The roads minister even promised to look at a more ambitious proposal, suggested most recently by Infrastructure Australia, to bring all Sydney's toll roads under common ownership, and equalise the charges so they are consistent across the city.

In theory, this would benefit residents who regularly use the heavily-tolled corridor of the M2, Lane Cove Tunnel and the Harbour Bridge.

''There are a lot of people suggesting that that's something that should be looked at in the future, to have an equalisation to make it fairer,'' Mr Gay said.

''It is certainly something I believe needs to be looked at and when I meet with Infrastructure NSW I'm going to suggest as one of the things that they should be doing.''

The infrastructure lobby group, Infrastructure Partnerships Australia, called on the government to act on the proposal to integrate tolls across Sydney to remove the burden on motorists from the north west.