What if we don’t build the CBD Rail Tunnel?

Work on the review of the CBD Rail Tunnel’s business case must be reasonably well advanced by now, with cabinet due to make a decision on the “where to from here” question in April, so that any government support of the project can be plugged into the figures for the May budget. As I’ve outlined before, government funding for the project probably isn’t needed for at least four more years, while Auckland Council and Auckland Transport sort out the detailed design and acquire the necessary resource consents. But it will still be interesting to see the results of the business case review – to gain a better understanding of the project’s benefits and fill in some of the gaps that the business case didn’t cover.

One of the key questions the review will probably look at in a bit more detail is the issue of “what would happen if we didn’t build the tunnel?” In essence, there are two possible alternatives – the ‘do nothing’ and the ‘do something else’. Under the ‘do nothing’ scenario, we all know that Britomart’s capacity will be exhausted fairly quickly, future increases in people travelling to the city centre would need to be accommodated by bus and car, congestion would worsen and, over time, the city centre would reduce in attractiveness as a place to live, work and visit. It’s fairly unlikely for absolutely nothing to happen to the transport system, so a key point is looking at the “do something else” options – then analysing their costs, benefits and how they compare with the CBD Tunnel.

This was something I thought the business case did reasonably well, but which I imagine the review will expand upon further. Appendix D to the business case outlines the alternatives in the most detail. First of all, the current transport problem – particularly in terms of getting access to and from the city centre – is described: The above information simply reinforces that “do nothing” is not really a viable option, unless we want the city centre to choke with bus and car congestion.

In addition to the CBD Rail Tunnel, two alternatives were considered as the main “do something else” possibilities. These were improved on-street bus lanes and a new underground bus tunnel. If we start first with the on-street one, this would obviously be the cheapest – and is described in more detail below: A helpful diagram, with the projected number of buses likely to use the different on-street bus priority routes, is included in the business case and shown below: This option still requires quite a lot of infrastructure upgrades to make it feasible: Even with the infrastructure upgrades outlined above (or without them because they’re impossible to achieve) this option has a number of potentially fundamental problems – which are detailed further in the alternatives assessment: If one was simply going for the cheapest option that might be able to cater for the increasing number of people getting in and out of the city centre, then this option might be it. However, the impact of the option on the quality of the city centre, the impact on key roads that connect to the motorway system (something that NZTA are probably more concerned about than me) and the lack of benefits that would be delivered to people outside the CBD put some serious questions in my head about the option.

I imagine the review of the business case will pin-point, in greater and more precise detail, the disbenefits of this option in monetary terms as the analysis in the alternatives assessment is quite subjective (though still highly valid in my opinion). One particular thing I hope the review will focus on is the monetary cost of operating 88% more buses to the CBD under this option. As most of them would be for peak time runs (and therefore the buses are used quite inefficiently) the ongoing operating costs necessary to make this option work might be astronomical.

The other option given serious consideration was an underground bus tunnel passing across the CBD – effectively linking the Northern Busway with high frequency corridors to the south via a completely grade separated tunnel with three underground stations. Its alignment is shown in the diagram below: One advantage of this option, even over and above the CBD Rail Tunnel, is the creation of a high capacity PT link between the Harbour Bridge and south of the city centre. Furthermore, this tunnel would take a huge number of buses off the city’s streets – with the only remaining buses being those from the west, Tamaki Drive and the western bays (in addition to the route shown in green).

However, it also has a number of disadvantages. The obvious one that immediately jumps to mind is that at the southern end, you couldn’t just pour 500-odd buses per hour onto Khyber Pass and New North roads without some serious upgrades to their bus infrastructure. In fact, to support the tunnel you would need to improve bus priority along extensive parts of many roads near the tunnel’s southern portal: I really struggle to think how you could build a busway (presumably something of the standard of what’s proposed for Ti Rakau Drive as part of AMETI) all the way down New North Road to Mt Albert or through Newmarket and then down Great South Road to the intersection with Main Highway. The cost, and urban effects, of undertaking such projects would be pretty massive.

Ultimately the biggest argument against the bus tunnel is its cost – which significantly exceeds that of the rail tunnel (both in terms of capital and ongoing operational costs): The different options (plus the option of simply expanding the Britomart tunnel to three tracks) were assessed against a variety of criteria. Somewhat strangely, only the CBD Rail Link and the bus tunnel options were fully assessed in terms of their cost-benefit analyses (maybe something else the review will look at). They were generally ranked from 1 (worst) to 3 (best) against a range of matters, which were at first unweighted and then weighted (giving strongest emphasis to low whole of life costs and conventional benefits). The analysis is shown below: Once added up, and weighted accordingly, the final result of the analysis showed below: It’s probably not that surprising the on-street and expanded Britomart options score relatively low – their benefits are minimal (but of course so are their cost). One thing that I would imagine the review of the business case will do is examine these other options in a bit more detail – highlighting the additional infrastructure requirements, the limitations of their benefits, the ongoing operational cost matters and so forth.

Overall, it seems pretty obvious to me that the two main alternatives considered: on-street bus improvements and the bus tunnel, aren’t particularly feasible. The bus tunnel, in my opinion, is particularly pointless as it’s much more expensive than the rail tunnel. This leaves the main comparisons between the on-street bus improvements and the rail tunnel – and I suppose some expansion of Britomart’s capacity by adding a third track. Looking at expanding Britomart first, while this may alleviate some of the immediate capacity issues of the station, it doesn’t improve rail access to the remainder of the city centre and it doesn’t offer a long-term capacity solution as ultimately the city centre is still being fed through two inbound tracks – one from Newmarket and one from Orakei.  There are also no travel time improvements for the Western Line. It is, at best, a short-term solution.

Looking at the bus surface option, my worry is that it would effectively ruin the city centre for pedestrians in the longer term by simply having so many buses on the streets. Less of a concern to me, but probably of a concern to NZTA, would be the significant impacts on the city centre’s road network and particularly on roads feeding the motorway system. In terms of sheer feasibility, I simply don’t know if accommodating all those buses is possible. Doing so would seem contrary to efforts to increase the pedestrian friendliness of the city as well.

In the end, the ‘do something else’ options, as alternatives to the CBD Rail Tunnel, just simply don’t make that much sense. I think the predominant reason for this is the enormous latent capacity of the existing rail system, that needs to be unlocked by the tunnel project. No alternative can do that, and therefore all the alternatives effectively require additional capacity throughout the city centre and its surrounding suburbs that simply cannot be feasibly provided.

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