The seating capacities of the 3-car Long-haul VLocity are:
DM(D) - 48 (includes 2 x 4-club seat arrangement)
TM - 30 (includes 4 x 4-club seat arrangement with shared tables)
DM - 66 (includes 4 x 4-club seat arrangement)
Total - 144
(Classic VLocity – 222)
DM(D) - Driver Motor with Disabled Toilet
TM - Trailer Motor, includes MCF.
DM - Driver Motor
In addition, the TM has 4 x side-facing fold-up seats in the buffet area (hereinafter referred to using its Dept of Transport brochure nomenclature of ‘MCF - modern catering facility’) and 4 x standard seats for wheel chair companions. There are 12 x side-facing fold-up seats in the 6 x wheel chair bays in the DM(D) and TM cars.
Assuming the diagrams are to scale, in a 2 x 3-car LH VLocity the two unused driving modules (12 each) and the extra MCF (30) take up space for about 54 seats. The extra MCF will presumably require an extra staff member.
Adding an additional car (TP?), similar in layout to the DM above, but without the driving module, to a 3-car LH VLocity would add 78 seats. Adding 2 x TP would roughly double the capacity, although, depending on the number of cars added, additional toilets and wheel chair bays would be a consideration. The additional cars could be designed to be added or subtracted subject to seasonal demands and allow splitting the train into 3-car units or less (with hostler controls if necessary) for maintenance. Obviously, the walk-through design obviates the need for the extra MCF.
The LH VLocitys probably only need to be capable of 130 km/h. Even on the BG RFR sections, such an express would be able to keep up with a Classic VLocity making extra stops. In a 5-car configuration, one of the additional TPs could be unpowered. In the event of an engine failure, there would still be 3 engines available.
The 2 x 3-car configuration seems a rather expensive way to minimise bustitution. One of the most recent major bustitution causes was the Wallan XPT derailment. A bigger fleet would provide extra redundancy. It should just be a matter of changing the wheelsets to switch from BG to SG or vice versa.
Still, one shouldn’t look a gift horse in the mouth. The LH VLocitys could be re-configured at a later date, much the same as the first VLocitys were converted from 2-car to 3-car.https://transport.vic.gov.au/-/media/ne-line-factsheet.pdf?la=en&hash=B93203FB732D925EFFCD5E1BC1A19A77