Using the Sydney Airport Link and also Brisbane Airtrain on several occasions the one thing recently which really made me think about airport rail services is there absolute need to be reliable 24x7. Sydney Airport has what seems to be a maximum 10 min interval between services meaning you never think about the possibility of being late for a flight even though I leave plenty of time from the CBD office to the airport.
The distance at Sydney is around 12 kms but this is a lot longer for Melbourne and given the track record of operators in Melbourne reliability is going to be a significant test of user acceptance.
Therefore reliability must be paramount in the planning of the link and this in itself concerns me as this is not what appears to happen in the network management in Victoria. How or what is the best way to bring service reliability to the forefront of planning and design for this link?
24/7 is unnecessary, impossible and a waste of money. You wiill find most Airport services are around 18-20h a day, typically midnight to 5am there are no services due to a combination of lack of demand and maintenance access time.
Brisbane airport had no flight curfew, but used to at least have a rail curfew for noise reasons where the Viaduct runs near the houses. having flown in last year at 11pm, I was picked up by car and had there been a train there would have been lucky to be a maxi taxi or 3 full for the two services that followed the flight, after that (I waited 1h for my ride) it would have been empty as Australia has very few domestic services flying after around 10pm at night.
When Brisbane first started it was mostly a 30min service and I was commuting from Brisbane to Gladstone weekly Friday PM for 18mths, sometime I took the RTT and other the plane, about 50:50 as company paid once a month only. (The QR phone booking staff knew me by name, hence "RTT Rules") Anyway I used to make sure I caught the airport train before my absolute cut off airport service just in case, especially as flights to Gladstone are few and far between.
As for Melbourne, if the service is 20min frequency for most of the day (most practical if there are no or few new other stations), then with a 95% reliability it should be fine and the Mel population which are already PT friendly will take it up quickly as the distance is significant and hence usually makes PT more attractive over taxi/rideshare and private car. A train with a good average speed exceeding 70km/h will help as well.
Last I looked Brisbane train was around 15% of airport flyers and Sydney pushing 20%, I would expect Melbourne to exceed 25% within 5 years of opening, which is 10mpa. It would help if the stations in the city were attractive to people being dropped off / pickup up. By this I mean Airport trains can be attractive for those with baggage, especially if the trains and stations cater for people with baggage, but not always the local services.