The free tram area, supported by the government and opposition, will be introduced from January 2015 and cover most of the traditional CBD and Docklands, stretching from Flinders Street to Victoria Street and Spring Street to Docklands.

But key tourist attractions such at the MCG, the National Tennis Centre, St Kilda Road and Melbourne Museum are outside the free ticket area.

When extolling the benefits of the free trams for tourists, Premier Denis Napthine on Sunday named several sites outside the free zone.

"It will also be magnificent for our interstate visitors, whether they are coming here for the spring racing carnival, the footy finals, the tennis open or whether you are coming here for a whole range of major events like the formula one grand prix," Dr Napthine said.

The government's media announcement hinted the free zone might not go far enough for some.

"Walking is a great way to explore any city and major attractions such as Melbourne Museum, Southbank and the National Gallery are a short walking distance from the free tram zone," Dr Napthine said in the release.

Public Transport Users Association president Tony Morton said: "We really don't see what the whole point of this free CBD tram service is."

He said many visitors would still need a myki card.

"I think visitors to Melbourne are going to want to venture outside the Hoddle grid; there is only so much you can do there, especially on weekends," he said.

"Even a short-term visitor would want to venture beyond the confines of this free travel zone," he said.

More than 70 tram stops in the city will have new signage indicating they are in a free tram zone and the government said there would be a "public information campaign" in coming months to "enable the smooth introduction of the change".

There is also concern the free CBD tram service may lead to more fare evasion outside the CBD.

"There is a lot of fare avoidance happening on trams as it is, because we are still running trams on an honesty system and we have done that ever since we got rid of the tram conductors," Dr Morton said.

"Some people may try and game the system and travel one or two stops outside the free area without touching on," he said.

The head of Yarra Trams Clement Michel conceded if people got on a tram before the CBD and did not pay and made it into the CBD without being detected it would be impossible to detect them inside the CBD.

Mr Michel would not say where inspectors would be, but that they would be redeployed under the free trams policy.

Almost one in 10 people do not buy a ticket on Melbourne's trams.

Public Transport Victoria said 9000 on-the-spot $75 penalty fares had been issued since August.

A little under a third of commuters caught without a ticket are opting for the $75 penalty fare instead of waiting for the $217 ticket infringement notice.

The latest Public Transport Victoria performance bulletin to June 2014 found the fare evasion rate across Melbourne's public transport network had fallen from 8.9 per cent in October 2013 to 8.7 per cent in May 2014.

The May 2014 fare evasion survey (taken before the new on-the-spot penalty fares were introduced) shows a drop in the rate of fare evasion on Metro trains, down from 8.4 per cent in October 2013, to 6.3 per cent in May 2014.

Fare evasion on trams was at 8.8 per cent in May 2014, up from 8 per cent in October 2013, but is well below 2011 tram fare evasion levels.