A subsequent Submissions Report announced a switch to single deck trains by stating:
The rapid transport network would not result in any substantial changes to Stage 1 of the NWRL project as described within EIS 1.
EIS 2 describes the tunnel diameter as now being 6.0 metres, which is suitable for single deck trains but no longer able to accommodate the current profile double deck trains envisaged in EIS 1. The arguments presented in support for Tier 1 rapid transit single deck trains appear intended to achieve approval of the smaller tunnel diameter by default on a fit for purpose basis.
This submission addresses some dubious aspects of these supporting arguments, and concludes that there is insufficient justification for changing the currently approved 6.6 metre diameter tunnels and thus preventing the use of double deck trains in the longer term. Comments on other aspects of the single deck train design described in EIS 2 are also included in this submission.
Each single deck train offers similar total capacity to a double deck train, but with fewer seats. However more trains per hour can be run due to lower dwell time from more doors and the lack of internal stairways. Indicative capacities based on adequately wide platforms, modern signalling and unrestrictive track alignments near stations for 160 metre trains are:
Rapid Transit single deck trains offer other advantages. Lower dwell times and better acceleration mean higher average speeds. Higher frequencies and simpler networks also allow freedom from a public timetable, and thus even faster average speeds under light loading conditions. Single deck trains would individually weigh less, consume less energy and have better energy recovery, cost less to buy and would be more suitable for one man operation.
The offering of more frequent single deck services (than would have been provided with double deck operation on the NWRL) to provide approximately the same number of seats per hour, confirms the above seating expectation. The additional services negate many of the benefits of single deck trains which depend upon more passengers being willing to stand. As well as the consequent lighter loading per train reducing maximum line capacity (and thus leaving less spare capacity for a Parramatta - Chatswood shuttle), costs and energy consumption would be higher due to the provision of additional trains, and frequency is not a very significant user issue above six trains per hour. This leaves some residual time benefits due to better dwell times, acceleration and the absence of timetable recovery time allowances. The willingness to incur additional operating costs seems irrational against seeking to use budget revenue more efficiently, and suggests that there could be another (black box) agenda.
In the longer term, these single deck trains and any others purchased should then be redeployed to where the costs and energy benefits that depend on a willingness to stand can be more fully realised. South side candidates would be the four inner area lines (Hurstville, Revesby via Airport, Bankstown and Strathfield) as well as the ESR and the proposed Sydney CBD/cross Harbour link. On the north side, a tier 1 service on the existing route from Waverton (linking to the cross Harbour link) to Gordon and a new link to the Peninsula, to better utilise the additional cross Harbour capacity, would be suitable. This would leave the NWRL and the ECRL to then revert to double deck operation, with these services joining those from the upper North Shore/Central Coast over the Bridge on a new route from North Sydney to St Leonards extending through Chatswood to Gordon.
There would also be relatively more user time benefits per kilometre (a larger impact on average speed) from better dwell time and acceleration on these inner lines if converted to tier 1 operation, due to the closer station spacing. For example, the 1.1 km average spacing for the Central - Strathfield line is significantly less than the 3 km average for the NWRL; yielding around three times the impact on average speed.
It is also important to manage the gap between platform and train so that it is narrow enough to minimise delays to boarding or alighting. In this regard, a three doorway per car configuration would also have unequal gaps where deployed on Sydney's legacy curved platforms. A 400 metre radius curvature leads to an estimated 100 mm gap differential between the centre and end doorways, with inversely proportional amounts for other radii.
An alternative train configuration to achieve equal and smaller platform gaps for all doorways would use two doors per shorter car with articulation to contain the bogie count. For example, a train of 12 articulated 13.5 metre sections would also have 24 doorways and, assuming two independent halves; a total of 14 bogies (cf 16 for a train of 8 standard length cars). A 10 x 16 metre configuration with 20 doorways and 12 bogies would also be possible.
It would therefore be imprudent to reduce the tunnel size and station clearances on a fit for purpose basis to accommodate only single deck trains, and EIS2 has not established to the contrary due to its poor differentiation between the benefits of single deck trains in general and benefits specific to the NWRL. Accordingly, 6.6 metre diameter tunnels and matching station clearances should be retained to enable double deck trains to be accommodated in the longer term.