Options for extending light rail to Johnsonville

This quote is an extract from an email, to FIT and others, about light rail service to Johnsonville:

…this points to the fact that the Johnsonville line at the very least should be extended through town. ... [A] single 20 km line is vastly superior to two isolated end-to-end lines heading off in opposite directions and sharing a common terminus, each with its own depot, with different vehicles types, and ... running on different gauges. Once you come to accept this and allow vehicles of four-car Matangi unit length (actually 86 m) through the streets during peak hours, then surely using the existing 1067 mm gauge is a no-brainer.

Teasing this out needs definitions:

Light rail
Rapid transit, usually either low-floor vehicles running on-street, or high-floor on separate rights-of-way. Street running light rail has on-street priority and a low-voltage overhead power supply (generally 750 V). Track gauge is usually ‘standard’ (1435 mm) or ‘metre’ (1000 mm).
Matangi
The main-line passenger trains used in the Wellington area, running in trains of two, four, or six cars, or potentially eight cars after lengthening platforms. Track gauge is 1067 mm.
NZR FP Class 4103 at Khandallah Station / Wikimedia Commons CC BY-SA

NZR FP Class 4103 at Khandallah Station / Wikimedia Commons CC BY-SA

The FIT view on extending light rail to Johnsonville is this:

  1. A single 20 km line is generally better than two 10 km lines, and FIT has no objection to railway vehicles running between Johnsonville and the Airport.

  2. The Johnsonville Line is single-track, and trains can only pass at Wadestown Loop, Ngaio and Khandallah. This is enough for four trains an hour each way, the present-day timetable (service every 15 minutes). Anything more would require double-tracking, because additional passing loops are impractical and offer only limited improvements to service frequency. 

  3. The Johnsonville Line is now operated using four-car Matangis at peak hours, and two cars at other times. These vehicles could readily be transferred to other lines.

  4. Introducing light rail on the existing single-track line would severely limit capacity. Conventional vehicles are typically 30 to 60 metres long, and regulations often set a practical on-street maximum of about 72–75 m. For example, the Siemens Avenio comes in standard lengths at multiples of 9 m, from 18 to 72 m. FIT has planned for up to 66 m vehicles—following Auckland—with a crush-loading capacity of 470 passengers (4 pass/sq m). Conversion to light rail would cap line-capacity at 1900 passengers an hour, about a third of its ultimate capacity using Matangis.

  5. The Johnsonville tunnels are too small for the vehicle-width chosen by Auckland Transport (2.65 m). On-street light rail is low-floor, with a platform height of about 350 mm, and the Johnsonville tunnels are very narrow at rail level.

  6. The Johnsonville Line should not be seen as just for commuters. Urban transport is changing fast, world-wide, and light rail can be expected to provide an all day, every day, frequent service. FIT is proposing a 5 minute service on some sections. Another likely improvement is bus hubs at Khandallah and Crofton Downs, improving local connectivity.

  7. The best available alternative to leaving the Johnsonville Line as-is will be rebuilding in double track, but with long tunnels it will be costly. If and when it is considered, three options seem plausible. All start at a light rail stop in the Railway Station forecourt: 

    • Up Molesworth or Murphy Sts (or a split route using both) to a stop at Park Rd (just beyond Tinakori Rd) then in tunnel to join the Johnsonville Line above Tunnel 5 (Hannover St, new tunnel length 1300 m).

    • Along Thorndon Quay to a stop at the end of Tinakori Rd, then in tunnel to the same point above Tunnel 5, also 1300 m.

    • Along the Hutt Rd to Kaiwharawhara, with a stop, then up the Ngaio Gorge on a combination of cuttings, viaducts and short tunnels. This route takes advantage of light rail’s hill-climbing capability and should be cheaper than tunnels, but it might not be consentable.

  8. In all these cases, the existing track through the railway yards could be converted to a fourth main-line, and the existing Ngaio Gorge tunnels converted to a cycling and walking route. Light rail extensions beyond Johnsonville would be possible. The route might be on stilts down the centre of SH1, to Glenside and perhaps on to a main line hub at Tawa.

  9. Use the same light rail standards as Auckland, including standard gauge track. This would open options for cost-savings through repeat orders.

  10. FIT proposes that the Railway Station to Airport route be built first, followed by an extension to Johnsonville and beyond. if and when funding is available.

  11. There are no technical barriers to converting the Johnsonville line to double-tracked light rail, if there is the political will. Similarly—if funding is available—Wellington could build the whole line starting now.