Converting the Onehunga Line to Light Rail – Extending Reach of both Heavy Rail and Light Rail!

$400m gives us three fold increase in service frequencies

After I had published my Light Rail for $2.5 Billion? Possible? Yes While Improving Accessibility and Social Equity earlier in the week it was raised with me “what about converting the Onehunga Line to Light Rail?”

The Onehunga Line is a short 3.4km single track branch line (with a passing loop at Te Papapa) between Penrose and Onehunga. It was reopened in 2010 and the first Line to run our current electric trains. The Line was designed to be double tracked ($600m) in the advent that Airport Rail (City Centre to Airport via Onehunga (heavy rail)) was to come to fruition. However, with the push for Light Rail (City Centre to Mangere via Dominion Road) the Airport Line via Onehunga as it were fell away as did the need for double tracking (pre City Rail Link). Consequently Onehunga Line services run every 30mins all day taking up valuable trains and slots at Britomart Station that could be used to extend services on the Southern or Western Lines.

Replacing the Onehunga Line with Light Rail while increasing frequencies 3-fold.

Unless the Onehunga Line is double-tracked (for an eye-watering $600m) the Branch Line is to be honest getting in the road of the Southern Line which the Onehunga Line also runs on. Given Onehunga services do not stop at all stations the value of the Line could be questioned. Post City Rail Link (2024) it is theorised Western Line services would use the CRL then continue to Onehunga before backtracking and heading back west via the CRL. Again this would need the $600m double-tracking investment that would already add to the $3.4b cost of the CRL. What is more likely to happen is Western Line services will continue to/from the West through the CRL and down the Southern Line but terminate at the currently unused Platform 3 at Otahuhu. To me this would be perfect for a number of reasons:

  1. Very little upgrade of existing infrastructure (basically all that is needed is two sets of points and some track at Platform 3, Otahuhu to make the platform operational
  2. Terminating Western Line services connect to Southern and Eastern Line services at Otahuhu
  3. Between Penrose and Newmarket (as well as inside the CRL itself) the combination of Southern and Western Line services at every 10 minutes means trains at the respective inner-stations every five minutes. Great for peak services

So what to do with the Onehunga Line?

We convert it to Light Rail between Onehunga and Penrose as seen below:

Extending City Centre to Mangere (navy blue) to replace the Onehunga Line to Penrose.
White = East West Link Highway
Yellow = existing heavy rail (Southern and Eastern Lines)

Regardless of what happens with City Centre to Mangere (City Centre to Onehunga) the Onehunga extension of Light Rail connecting CC2M to Penrose allows the following:

  1. Increase of frequencies between the two points from every 30 minutes as current to every 10minutes at minimum
  2. High frequencies on both the Onehunga LRT extension and the Southern Line (every 5-10mins) means walk-up and go services and seamless transfers
  3. Once CC2M reaches Britomart via Dominion Road the Onehunga LRT extension can still operate – you are still going to get to Britomart
  4. Light depot would also be built at Onehunga allowing stabling and light maintenance of the LRT fleet (the heavy depot is at Puhinui)


Using the $75m/km cost I did with Airport to Botany converting the Onehunga heavy rail branch to Light Rail would nominally be: $255m. However, I have rounded it up to $300m to allow heavy track removal, property purchases at the Onehunga end and a level crossing removal at the Penrose end.

The extra $100m allows for:

  • Station retrofitting
  • Extra rolling stock
  • Light Depot and trackwork at Onehunga

Total price $400m for increasing your services from every 30 minutes to every 10 minutes allowing seamless transfers at Penrose.

Wouldn’t this make Airport to Botany redundant?

Given Airport to Botany is touted as the express link to the Airport (using the combination of Southern Line and the A2B services) the Onehunga LRt extension would give another option to the Airport that is for sure. But it does not make A2B redundant due to:

  • Route is an east-west one servicing a catchment not done so by rapid transit already
  • People or employment south of Puhinui needing access to the Airport would use A2B
  • Having two Airport Lines that connect to our heavy rail network is never a bad thing on redundancy grounds
A2B plus 20connect Source: NZTA

Converting the Onehunga Branch Line to Light Rail allowing City Centre to Mangere Light Rail (well Airport to Onehunga at the moment) to be extended and connect up with existing heavy rail services at Penrose, a good deal for $400m? Given frequencies would be increased from the existing 30 minutes under heavy rail to 10 minutes under LRT while not needing for expensive duplication of heavy rail ($600m) and freeing up rolling stock for other services; I say a very good and prudent deal.

Especially in due time the LRT extension could continue to Ellersile, snake around and head to Panmure and out to Botany replacing the Eastern Busway and connecting to Airport to Botany at Botany!

One thought on “Converting the Onehunga Line to Light Rail – Extending Reach of both Heavy Rail and Light Rail!

  1. Good idea – it could also form part of a cross-town Light Rail route from Avondale or New Lynn

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