This is a guest post from reader Axio
Peter’s post on the future of driverless light-metro got me thinking about whether there are alternative alignments where an automatic metro could be used, and I felt that it would be a cost-effective solution to mayor’s vision of rail to the Airport and the North Shore.
Many proposals presented in this blog focus on connecting a North Shore line with the City Rail link by crossing at right angles at Aotea station and tunneling under the university to come out somewhere on the Eastern line. This minimizes the additional infrastructure needed on the city side of the link. However tunnels are very expensive and if an elevated metro is used then we might find that we can achieve much more substantial system for a similar cost.
This alternative considers a line from Takapuna through to the Airport. This would be a driverless metro elevated along its entire length, except possibly the harbour crossing. The proposed alignment is illustrated below.
The benefits of this alignment are many:
Obviously this provides rapid-transit to the North Shore, Mangere, and the Airport, meeting the strategic goal. It brings Takapuna onto the Rapid Transit Network (RTN), which is useful as it has been identified as a commercial centre in the Auckland Plan. This also makes the CBD much more accessible from western South Auckland.
- Leverages the most effective part of the Northern Busway by providing a high frequency connection at Akoranga. If most buses terminated at Akoranga then the lowest capacity and slowest section of the busway (the harbour bridge and CBD) would not be required for the bulk of trips.
- Replaces overcrowded bus routes on Dominion Road, and in doing so takes the pressure off Symonds Street. It also allows Dominion Road to retain its on street parking which was a sore point during the submissions into Light Rail on the corridor.
- Connects into the existing rail network at Onehunga and Mt Eden (depending on where stations are placed following construction of the City Rail Link).
- Provides another access point to Eden Park along Bellwood Avenue.
And overall it brings together parts of Auckland that are presently quite separate as far as transit is concerned.
For automatic metro the line requires its own right of way which would be achieved largely using elevated rail. As most of the line is above road corridors, this would require a viaduct composed of single columns about 4.5m high with the rail deck around another metre higher. Stations would be spaced every kilometer or so. As mentioned earlier the harbor crossing may be tunneled, and the section along SH20 could be at ground level in places.
There are some challenges inherent in the alignment and terrain. The section east from Hillsborough Road to sea level will be quite steep and probably require a viaduct that extends well east of where SH20 flattens out in order to reduce the gradient. Similarly the section through the CBD will be quite steep, although with a station in the middle the slow speeds due to gradient will be less painful to passengers. Getting through the CMJ can be done using the old Nelson Street off ramp from the Southern Motorway followed by a viaduct over the CMJ once clear of K-Road. The corner at Wellesley and Hobson is quite tight, although the radius exceeds the 35m mentioned as the limit for this type of metro as shown.
This brings us to the big question: what will it cost? In this case I will just look at the section from Wynyard to Onehunga as costings for heavy rail north and sound of there can be found in other documents and provide a reasonable indicator of cost (particularly to the north where the cost is largely due to the tunnel).
The Vancouver Skytrain provides the most useful estimates as it is the system on which this is based. South Fraser Blog quotes On Track: The SkyTrain Story which indicates the cost for the elevated only section is around $47million per kilometer in 2012 Canadian dollars. At the present exchange rate this comes out to about $60million per kilometer so the line from Wynyard to Onehunga, at around 14km, would have a baseline at $840 million. Building above a road corridor would likely increase the cost, and we also have to deal with the special viaducts at the CMJ and Onehunga. Finally that estimate does not include the cost of the trains.
Compared to the Waterview Connection and the City Rail link this project, at a little over a billion dollars, is relatively inexpensive given the area it provides service to, although obviously much of the benefit would come from the un-costed sections from Wynyard to Takapuna, and Onehunga to the Airport. It does also have the ability to be built in sections with each section providing significant benefits on its own. For instance Wynyard through to Bellwood Avenue would provide a different place for Dominion Road buses to terminate, and still connect the Isthmus and West to Midtown and Wynyard.
The cost not-with-standing, an elevated metro has a significant downside, visual pollution. A 5.5 metre viaduct will stand-out in all but the CBD, and as Dominion Road has something of an iconic status this visual pollution may be unacceptable. There are alternative corridors through the isthmus such as Sandringham Road which would have the benefit of being closer to St Lukes, a major attractor, but increase the overall cost and the journey time from the North Shore to the Airport.
Finally, while this line is intended to complement the City Rail link, it does have potential to stand on its own, providing rapid transit access to Midtown from the central slice of the city (from the Airport to Albany) and the West, assuming a transfer at Mt Eden. However it would not be connected to the East of the city, and so its benefits would be reduced without the City Rail link.