Saturday, 22 May 2010

Avondale-Southdown Rail Corridor

Auckland Transport posted on this corridor a couple of weeks back and by coincidence I was looking at it on my map of the NAL today. The idea is that there would be a freight train bypass of the busiest part of the passenger service lines between Avondale and Southdown. The latter has a major freight terminal long established. However, the area which would be served by this freight traffic is primarily Northland which has its rail link currently under review. Scott also says the “incline” of the route limits the length of trains that can be carried on it. Southdown is at around 10 metres altitude and Avondale around 40. This would produce an average gradient around 1 in 400 which is not a big deal. Google Earth data, however, backed up by topo maps, suggests that a train from the Avondale end would have to climb 20 metres in the first (approx) 1.5 km, a 1 in 75 grade which is pretty steep by modern standards. After that the track would be roughly level for a while before it descends on, probably, a similar short sharp grade, and then another longish levelish stretch to the freight yard at Southdown (All numbers are approximate as I haven’t seen any survey data). The line passes close to Mt Roskill, a hilly part of Auckland. The grade could be reduced by substantial earthworks or even tunnelling but this would add greatly to the cost. There has been a designation of the corridor since 1947 but it seems unlikely it will ever be built in the current scenario.
Currently, the Waterview Connection motorway (SH20) is being developed alongside, and probably through, a significant part of the rail corridor. The motorway is going to be tunnelled through some areas where houses have been built, and in other areas houses are being demolished. It is possible that parts of the designated corridor have been reassigned to the motorway as Auckland Transport points out.
This map of the NAL shows an approximate route of the corridor (green line)

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If we zoom in on the Avondale end, we can see that the land designation has had an impact on adjacent properties. A short part of the Avondale end has appeared on my maps for years.

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In spite of that triangle leg going through a carpark, the designation is pretty clear on the map view of Google Maps (click that Map button above and you’ll see it).
Please note that as the map has been updated just today, all alterations may not be visible immediately.