At present, all T4 Illawarra Line (Suburban) and South Coast (Intercity) services terminate at Bondi Junction. There are 14tph T4 services from Hurstville, Cronulla and Waterfall and 4tph South Coast (Intercity).It's impractical to use the 10 car D sets on the North Shore Line or the Eastern Suburbs Railway and I'll demonstrate why.
Following the ATP/ATO upgrade, the overall frequency will be increased from 18 to 24tph. 3 of the current 4 SCO Intercity services, plus an additional service, will be diverted to Sydney Terminal. The other SCO service from Thirroul to Bondi Junction will be retained. That frees up an additional 9 paths for T4 services from Hurstville, Cronulla and Waterfall, the apportionment of which is still to be revealed.
As I said before, I doubt if 10 car D sets will operate via the North Shore Line or to Bondi Junction. They are likely to be operated by the shorter 6 or 8 car sets. There are no plans to extend platforms on the Suburban network that I'm aware of other than Waterfall.
My understanding is that there will be no eight car D sets.
At present, only 4, 6 and 10 car trains are authorised to operate.
The present contract delivers 55 ten car sets and one four car set.
Marshalling four car sets into eight car rakes means that there will be twice as many sets limited to six cars which will have relatively few seats for peak hour traffic compared to a six car V set or eight car H set.
As I've said, there is no good reason not to use ten car sets on the underground or at short suburban platforms. The train will detect from a balise on the track which doors on which side should be opened. It might be necessary to improve passenger information as to which cars will be in the platform in advance of the stop but this is no different to H sets on the North now.
The last two cars could display which stations they will be able to unload passengers. However, those cars provide seats for other passengers as long as they are aware that they have to move forward at many intermediate stations.
If the last 2 cars are unable to allow access to the CBD stations, then no one is going to board them even when they are able to at the outer stations with longer platforms. Conversely, no one will be able to board them in the CBD, regardless of their destination. They will largely be empty, so what's the point in having them? In the absence of any 8 car sets, they will have to be 6 cars in the peak if they continue on the North Shore Line or the limited SCO service on the ESR to Bondi Junction.
It's still not clear whether the Gosford/Wyong Intercity services will continue on the North Shore Line. They may all continue to Sydney Terminal via Strathfield which would require interchange at Hornsby for those wanting access to North Shore Line destinations.