Staging the CBD Rail Tunnel

As I have outlined in the past, Britomart station is a major bottleneck in Auckland’s rail network. There are only two tracks in and out of the station, which means that – at the moment – only 18 trains can get in and out of the station in an hour. By the end of this year that will be increased to 24 trains per hour, due to both the lines being able to operate ‘bi-directionally’ (trains running either way up and down the line causing fewer conflicts between trains). However, as I detailed in my post on Auckland’s rail plan a few days ago, it is highly likely that Britomart will reach capacity by 2016 – if not earlier.

The solution, as outlined in that rail plan, is for a rail tunnel to be built between Britomart and Mt Eden stations. This would create somewhat of a “loop” around the CBD and would mean that trains don’t have to terminate and Britomart and leave the same way they came in. This would double the capacity of the station and certainly at least buy us a few more decades before any further significant upgrades to Auckland’s railway system are necessary. The idea of a CBD rail tunnel has actually been around for about 80 years – first proposed in the 1920s. Further iterations of the plan emerged in the 1950s, while a similar proposal almost happened in the 1970s before an incoming National government vetoed the idea. Anyway, a few years ago the idea emerged once again, as rail patronage started to “take off” subsequent to Britomart’s opening. A study was commissioned, and outlined the following alignment as the prefered option:

Basically we end up with two additional stations – Wellesley (Midtown) and Karangahape. This would improve rail access to all parts of the CBD significantly and I think there is potential for the midtown station in particular to become even more popular than Britomart, given its location in the heart of Auckland’s CBD. Crucially, what we also end up with is the ability for trains from the west to access the CBD far quicker than they do at the moment as well as the capacity improvements that I talked about above. One way the system could operate is outlined below (assuming we end up with an airport line at some point):

Now this rail tunnel is obviously GREAT. Once electrification is complete I think it is Auckland’s most important transport project. More important than another harbour crossing (as the current situation works quite well), more important than rail to the airport (in fact you can’t actually have rail to the airport until you build this due to the Britomart bottleneck) and – in my opinion – more important than the Waterview Connection. The problem with this project is of course the price, which is fairly hefty at around $1.5 billion. It is worth noting that this is a very similar price to that of the Waterview Connection, but when we consider the current government’s transport funding priorities I can’t really see the CBD rail loop managing to find $1.5 billion of money any time soon. However, the capacity issues with Britomart are fairly critical – so could we do this in some sort of staged way? Perhaps so:

The above image proposes a three-step way in which we could build the CBD rail tunnel and future rail to the North Shore.

Step One: build a new two-track cut and cover tunnel along the route shown in blue. At Quay Park Junction organise the tracks so that ideally the Eastern Line can feed into this track without having to cross over any other lines. The Western & Southern Lines could also access this track if necessary, but typically they would continue to use the existing entrance to Britomart. Hopefully this would coincide with either triple or quadrupling the NIMT down to Papakura.There would be a new two platform station directly to the north of Britomart. The station would be shallower than the current Britomart station (immediately under Quay Street if possible). At a guess this project surely couldn’t cost much more than $300-$400 million. The station wouldn’t have to be particularly grand – I imagine it as something similar to your typical London Underground station, linked to Britomart’s first level down (where the toilets are). There may be a case for bi-furcated platforms here.

Step Two: continues the new line into the CBD rail loop. Link to Mt Eden. Step one means that step two could probably be put off for a few more years – then perhaps we will see what happens to patronage and whether there’s a point in having a four track tunnel. The Western Line would eventually link with the Howick/Botany Line along these tracks. Similarly a future Cirle Line could also pass through these tracks. (Hence the potential need for bifurcated tracks).

Step Three: takes the tracks that current go to platforms 1 and 5 at Britomart, continues them straight ahead, underneath the two tracks in Green (remember they are shallower than the current Britomart tracks) and eventually underneath Customs Street and Fanshawe Street to the North Shore.

Of course there are still some issues, like dealing with where the green and red lines intersect. There are also issues relating to whether the existing buildings (of future buildings that have been consented) could work in with this design. Furthermore, it does go against what is being worked towards at the moment (the very top image of this post). However, what step one of this proposal would do – quite crucially – is over a way in which the capacity constraints of Britomart could be eased as a relatively low cost and also relatively quickly. While the other benefits of the CBD rail tunnel are significant, easing the bottleneck is the most important and will be required first.