MM2 aside for a moment as this thread has gone a little sideways. If MM2 goes ahead rationalisation of Clifton Hill will be wrapped up with it. As has been mentioned ad lib, the cost and benefits of this project are fuzzy at best. With COVID19 pushing this project well into the 2030's once demand again dictates it. Lets assume its not happening anytime soon.
As for Clifton Hill, a lot of suggestions have been centred around solving the problem at Clifton Hill itself. As we all know, its a tight space, with some very obvious and challenging engineering considerations. I agree there is a need for four platforms at Clifton Hill, this adds greater flexibility for passengers and operations. So I've taken a leaf out of the LXRA book to deliver my armchair solution.
Build two additional platforms under Hoddle Street, in a similar fashion to they way LXRA builds a station under a former crossing.
Trench both lines, Hurstbridge declining from Merri Creek and South Morang from High Street/Queen Parade. Gradents may require the current rail over to become rail under.
Using the same techniques of sinking piles and peers into the ground to build retaining walls can be used to reduce the amount of time this small section of Hoddle Street would need to be closed. Once bridge decks have been installed works can continue underneath with traffic following over the top. As is done now by LXRA. To achieve the decent, Clifton Hill is moved towards Ramsden Street, with the new South Morang Platforms, new stations facilities sitting under Hoddle Street and new sunken platforms for Hurstbridge built on the current railway reserve. A new station entrance can be constructed in Mayors park, improving the connection to Trams on Queens Parade. Heritage listed station buildings are refurbished and given over to the community, similar to what has been done on the Frankston Line. We now have a brand new station with an underpass and platforms under Hoddle Street. Issue one Solved. Hopefully keeping the NIMBYS happy.
Aquire the commercial building at 420 and 424 Hoddle Street to accomodate the new four tracks and the climb out of the trench.
Modifications to the Roseneath Street overpass may be needed with the gradient. Between Roseneath Street and the Eastern Freeway the reserve is slightly wider and could possibly accommodate four tracks without acquisitions.
New rail bridge over the Eastern, with the rail fly over to be part of this. Track slews and the point work can be accommodated in the VicTrack owned land off Lulie Street, returning to two tracks at Victoria Park sans any conflicts.
This really only solves the conflict at Clifton Hill and like other suggestions, its going to be pricey no matter what you do here. To really justify the expense Moving Block signalling would need to be installed from Clifton Hill to Flinders Street, including the Loop to boost train paths to 32TPH. With this you could effectively run a 3 minute headway to South Morang and Greensbrough. Any such frequency would require the removal off all level crossing, adding more money. To which there will be 13 remaining to Epping and 6 to Greensbrough.
To release the benefits of Clifton Hill, its going to be north of $2 Billion. So it may be sometime before we see any major action at Clifton Hill, with the Government more likely to continue to remove LX on the lines before embarking on a major project that would see trains passing a level crossing every 90 seconds during peak.
Which takes me back to my opening statement. If it is going to be 10+ years before all Level Crossings are removed will successive governments leave Clifton Hill as is until MM2 becomes needed in the 2030's.