We will soon have 2 ring roads. Absolutely no need for a third unless they are planning for Melbourne to sprawl all the way out to Geelong, Ballarat and Shepparton. That is not implausible but ridiculous all the same. Freeways don't really discriminate in creating sprawl, they do it just as badly in the country as the city.
The unused infrastructure is already there to provide passenger rail links instead. Ring rail should be provided first and foremost as transit oriented development is much more sustainable and also creates better cities.
Geelong-Ballarat Railway is currently only used for freight but could easily support passenger services.
Reopening the disused Geelong-Ballarat railway to passengers is a no-brainer.
The line to Maryborough from Ballarat will be opened next year.
The Mildura line and Echuca to Shepparton are the missing links which all have existing rail infrastructure which can also be upgraded and used.
Rail use in Victoria is growing rapidly - private vehicle use on the other hand is not. Regional fast rail is significantly faster travel than the car, especially express services.
This sort of proposal is simply an excuse for the road lobby to remain relevant in an era when it is no longer sustainable with peak oil production already confirmed.
There is no way people are going to be able to drive from Geelong to Shep or Shep to Melbourne on a daily basis - now or ever. But providing people with alternative transport options - even just one or two services a day is a viable alternative.