An article in the NZ Herald today explores the possibility of looking at possibly up to four stations being constructed on the CBD Rail Tunnel – rather than the current proposal for two (well, really three if you count the relocated Mt Eden station). This idea has been floated by Mike Lee, the Chairman of the ARC and most probably Auckland’s biggest public transport advocate – so it’s something worth looking into a bit more. Here’s the relevant extract from the article:
Auckland Regional Council chairman Mike Lee has asked officials to consider adding more underground stations to a proposed $1 billion to $1.5 billion rail tunnel below the central business district.
He wants a $5 million study commissioned by KiwiRail and his council’s transport authority subsidiary to consider doubling to four the number of stations proposed for a 3.4km route between Britomart and Mt Eden via Albert St.
Until now, only two stations in the vicinities of Aotea Square and Karangahape Rd have been suggested for the study’s purposes of recommending a preferred route.
But Mr Lee has baulked at a suggestion by council member Joel Cayford, a former regional transport committee chairman, that the study also consider future underground connections in other directions from the tunnel.
“Let’s not get too complicated – this is about the CBD tunnel and we have to justify it to the Minister [of Transport, Steven Joyce] and as soon as possible,” Mr Lee told Dr Cayford and other councillors…
…Mr Lee, despite his cautionary advice to Dr Cayford, nominated Wyndham and Victoria Sts as possible sites for two extra stations to cater for a growing inner-city population of apartment dwellers.
Now let’s get a couple of things out of the way to start with. Firstly, it’s fantastic that this project is continuing to get more and more publicity. There now really seems to be some real momentum behind the CBD Rail Tunnel, and I am very much looking forward to the outcome of this research study into the tunnel. Secondly, I agree with Mike Lee that this is not the time to be looking at alternative alignments. The one chosen for further research is very similar to alignments that have been looked at over the past 80 years and it is one that makes a lot of sense. If there ends up being nasty unforeseen problems with this option, then I think we should look at alternatives – but for now I am really of the opinion that as much effort as possible needs to be put towards promoting this project.
So if we turn to the number of stations, as you can see on the hastily drawn map of the route I have done below, there will definitely be two new stations – Midtown and K Road – while the current Mt Eden station may well be shifted to the southern end of the rail tunnel so that it can provide better access to Eden Terrace.
While I agree with Mike Lee on most transport related matters, I must say that on this occasion I don’t actually think there is much point in building more than two stations. I have three main reasons for this opinion:
- Underground stations are really really expensive. Two more stations could potentially add up to $200-300 million to the cost of this project – pushing it out from $1.5 billion approximately to around $1.8 billion. I’d hate to see that being the difference between the project going ahead and not going ahead.
- The grades of the tunnel are already going to be pushing what is possible. The tracks aside platforms need to be pretty flat, which means that with four sections of flat track rather than two sections, the remaining area is going to need to be steeper to compensate. This might make the project technically unviable.
- The benefits of additional stations are relatively minor.
Working through these three points, I must admit the first one is largely guesswork. However, I do know that underground train stations are enormously expensive and difficult to build. Throughout the lower part of the CBD the train line will be travelling underneath Albert Street, which means digging down to build a large area for an underground station is going to be a challenging and very expensive job. This project is already expensive enough, and will most likely already struggle to get enough funding – so I see little point in raising the cost of it even further unless the benefits gained are particularly massive.
In terms of the grade of the tunnel, if we take the figure of the article above, the tunnel will be approximately 3.4 km long. The tracks at Britomart are a few metres below sea level at the moment, while the current Western Line at Mt Eden station is approximately 72 metres above sea level. Generally it is considered that a railway track should have a grade of no steeper than “1 in 50” (one metre up or down for every 50 metres across) for extended lengths, although there are some places where this is exceeded. Getting trains up around 75 metres at a 1 in 50 grade would take around 3.75 kilometres of track – which we don’t actually have here. Further complicating matters is that at stations you cannot really have a sloping track as it can be difficult for trains to get started and go uphill immediately – so we can effectively remove a couple of hundred metres from the total distance for each station that is included. Doubling the number of stations on the line would double the length of track that couldn’t be rising, which therefore increases the steepness of the track elsewhere in the tunnel. If we had four stations, each with say 200m of flat track set aside for station platforms and “vertical curves” (where a flat bit of track slowly becomes a rising or falling bit of track) that would effectively remove 800m of length from the tunnel, which is already arguably a bit too short for the climb it has to do. This might be the final killer blow for this idea, as it could make the whole project practically impossible.
The third point, is questioning whether we really need any more stations than the two currently proposed. More stations will slow down the trip, they will be expensive to build and so forth. All in all, for there to be more stations they need to be highly justified. To get some idea of how well the current station locations “cover” the CBD, I have used the trusty Google Earth to measure the distances between the stations on the northern side of where the railway line would go underneath the Southern Motorway. These are as follows:
- Karangahape Road station to Midtown Station: ~970m
- Midtown Station to Britomart Station: ~770m
Generally it is considered that 400m takes about 5 minutes to walk. So this means that even if you’re bang in the middle between Midtown Station and Karangahape Road station (which would be around the bottom end of Vincent street) you would still have not much more than a 5 minute walk to either of those two stations. If you were bang in the middle of Midtown and Britomart stations (around the intersection of Wyndham Street and Albert Street) you would have barely a 350m walk to either station – taking less than five minutes. So I really can’t see either of those situations being poor enough to justify the huge extra cost in having additional underground stations.
Overall, I don’t really think it’s worth pursuing adding any additional stations to this proposed project. I think it would work just fine with the suggested two main stations.