With the government supporting light rail, hopefully the team/s tasked with the project have now been able to move on from justification to delivery. While the high-level decision has been made, there’s still a lot of detail that needs to be worked out. One area we think needs a bit more debate is the route through the southern isthmus between Dominion Rd and Onehunga.
The current plan is to send light rail from the city down Dominion Rd to State Highway 20. It would then travel alongside SH20 to Onehunga where it would turn along Princes St to connect to the Train Station before continuing on to the airport. There would only be one station, at Hillsborough Rd, between Dominion Rd and Onehunga. From what I can tell there are a few reasons for that:
- In the trade-off between speed and catchment, speed appears to have been the only determining factor here.
- Motorways don’t make great public transport corridors. That’s because motorways tend not to be too welcoming towards people (noise, pollution etc). They also make accessing stations difficult for much of the catchment whilst simultaneously suppressing nearby development potential. After all, how many people choose to live next to a motorway. Motorways corridors are normally only used because they’re easier to deliver.
- There simply aren’t that many potential sites along that stretch of the route for a station.
We think an alternative could be to instead send the tracks along Mt Albert Rd, Mt Smart Rd and then down Onehunga Mall. This is shown below in blue, compared to the current planned route in red.
There are number of reasons why we think this option should be investigated and most of them revolve around serving more people.
As you can see immediately from the map above, the blue route passes by a lot more houses meaning it’s going to be more useful to more people. But what exists today is just the beginning. There’s a huge amount of development planned or allowed for along the route. For example:
- We already know that around 1,500 dwellings are planned to be built in the old Three Kings Quarry.
- Housing New Zealand are redeveloping many of their properties nearby, including many on the southern side of the mountain/quarry.
- The Unitary Plan allows for significant redevelopment at both Three Kings and even more so at Royal Oak. Both have considerable allowance for Terraced Housing and Apartments (orange). By comparison there’s very little development potential on the motorway corridor. This is shown below
Perhaps these development areas could be served by other light rail routes, such as as the proposed lines down Manukau Rd and Mt Eden Rd. However, AT and the Council have gone silent on these routes and they appear to have been quietly dropped. If those routes were eventually built they would still tie in nicely with this proposal.
Both routes are close to being identical in length however the blue route uses existing roads. They would still have be rebuilt, and maybe even widened in places but I imagine that it would still stack up well compared an entire off-line route with multiple bridge structures and other works. It also conveniently doesn’t require any of Kiwirail’s Avondale-Southdown designation.
Perhaps the key disadvantage I can see with this idea is the speed. On the red route, the motorway route would afford higher speeds than the Mt Albert Rd option. For this post I’ve estimated just how much difference that might make.
For the blue route I’ve assumed an average speed of 30km/h. That assumes vehicles would travel at about 50km/h along the street and have signal priority but would also have to stop at stations along the way. Based on the approximately 5.5km trip it would take 11 minutes to get between Mt Roskill and Onehunga. By comparison, for the red route I’ve assumed 30km/h for the end of Dominion Rd and on Princes St in Onehunga with 60km/h in between those two bits. That comes out at around 7 minutes.
A 4 minute difference isn’t so bad and there’ll also, even sooner, be the option of a frequent bus to a new Puhinui interchange where passengers can transfer straight to rail
Much of the route may require road widening and along with that changes to how locals use the street. That could lead to more people opposing the project and making it take longer. As mentioned earlier, motorway corridors tend to be easier to build, in part that’s because there fewer locals to complain.
A 4-minute extra trip to put light rail past 10’s of thousands of extra people seems like a debate worth having. What do you think?