^ The three minute increase in journey time by not running express Jolimont-Clifton Hill is not why the Hurstbridge line has little patronage outside of peak.
I wouldn't have said the Hurstbridge line has little patronage outside of peak. Sure it isn't the Dandenong line, but the train is usually comfortably full by Fairfield or so. I got the impression the stopping all stations off peak was to provide a 10 minute service frequency between Clifton Hill and the city. And as you point out, the 3 minutes is no big deal and would be saved by anyone getting off at the stations previously expressed through.
it 13 mins is difference between express train and stopping all stations train
Where the heck are you running express - from Hurstbridge? According to the current timetable, you can save 3 minutes running express from Jolimont to Clifton Hill, 4 minutes between Clifton Hill and Heidelberg (not stopping at Ivanhoe), and 2 minutes between Heidelberg and Greensborough (assuming platforms can be found - I don't know why so many counter peak morning trains run express between Heidelberg and Greensborough given the same timing is allowed for stopping, presumably because the express has to wait for a platform at Greensborough). 3+4+2 = 9 minutes according to my calculator. And this would be less than optimal as it misses busy stations like Watsonia, Macleod, Ivanhoe and Fairfield.
Seriously, I would love to travel express from Greensborough to whichever station I wish to get off at for that journey, but it's a train, not a taxi. In return for paying much much less than it would cost me to drive, I put up with stopping at a few stations along the way. Sometimes they are even where I want to go.
It would be waste of resources of having 10 mins services to place like Alphington, Dennis, Darebin and Eaglemont stations, but at same time places like Heidelberg, Ivanhoe and Fairfield should have a ten mins service: I would have include any station after Heidelberg till Greensborough - but there is problem of single track between Heidelberg and Rosanna station.
Nope, more just a waste of resources. The single track section easily copes with the better than 10 minute frequency in peak hour - there is no reason based on line capacity for not running a 10 minute service to Greensborough. In fact, the PTV in their train plan propose to do so some time before 2050.
That why train line needs a two tier service :
Etham (Hurstbridge every 2nd train) stopping all stations to Heidelberg then Ivanhoe and then Fairfield and then may be Westgarth and then Clifton Hill and then express to Jolimont and then to Flinders street (every 20 mins)
5 to 10 mins after the express service from Heidelberg and then run stopping all station from Heidelberg to the City (every 20 mins)
If you're going to run an express every 20 minutes and a seperate stopping service every 20 minutes, why not just run a stopping service every 10 minutes? Frequency is freedom as Jarrett Walker is fond of saying, a 20 minute service saving at best 9 minutes is still 1 minute slower than a 10 minute service stopping all stations if I've just missed one. In fact, worse if I have to go somewhere other than Heidelberg, Clifton Hill or the city.
This should allow the South Morang line to go express between Clifton Hill and Jolimont because stations like Victoria Park, Collingwood, West Richmond and North Richmond only get a small number of people using the service and these locations have lots of other services provide them with a more frequent service going to the city such as number of frequent smart buses and tram services.
So once you've closed Victoria Park, Collingwood, West Richmond and North Richmond or given them a rubbish service, how do people from north of Clifton Hill get to those locations? For work, or to eat at one of the well regarded Victoria St restaurants. Or to go to Ikea on the 109? To walk to Richmond station from West Richmond (slightly quicker than going in to the city and back out again)? Those stations don't only exist so locals can go to the city!
With all due respect, if saving 3 minutes is that important, buy a helicopter and fly to the city. Is the heliport still there?
Otherwise, plug your headphones into your iPod, get out your smartphone, go to Failblog, or YouTube cat videos and you'll be in the city before you realise you've stopped at West Richmond...