The release of the latest Auckland Transport Alignment Project two weeks ago included this comment about light rail.

“This ATAP will see our rapid transit network grow considerably. I’m looking forward to updating Aucklanders on the next steps for light rail next month,” Michael Wood said.

A similar comment was made by Deputy Prime Minister Grant Robertson at an event just over a week ago.

We’ll need to wait to see just what the announcement is but it almost certainly won’t be that the project is starting. Most likely it will be announcing the ‘public sector delivery model’ which was the next step announced last year following the mess created by the superfund process. Essentially this will be the Who, and it’s likely they’ll be tasked with (once again) working out the What, How and When.

Will the Ministry of Transport be given it to mess it up with a dodgy process a second time, will it be given to Waka Kotahi again, or perhaps even handed back to Auckland Transport – my guess is we’ll end up with some hybrid and all will be required to work together on it, along with the likes of the Council and Kāinga Ora.

As for what they’ll be working on, the first step will need to actually work out what the project is. The debate and uncertainty with light rail in recent years has resulted in more questions than answers and as such there are a series of decisions and/or trade-offs that need to be made. For example, the level of grade separation the route has, the actual route it takes, how much priority is given to speed vs coverage (number of stations/stop spacing), the level of level of future proofing, how it integrates with our existing system, any related public realm upgrades, the extent of integration with Kāinga Ora and other housing developments, and of course how long it will take to build and the cost.

Most of these trade-offs are extremely interlinked and with one side of the trade-off represented by the idea of either Light Rail or Light Metro. So with this post I thought I’d have a look at some of those trade-offs through the lens of those two solutions. I’ve covered many of these in the past, such as this post on making sensible mode decisions and looking at if it should be underground but it doesn’t hurt to revisit some of these.

There’s always plenty of debate about modes and technologies but these two are perhaps best described as

• Light rail – like what was originally proposed for the City Centre to Mangere corridor, a mix of on-street in dedicated lanes and off-road sections, similar to what’s been built in Sydney, Canberra, the Gold Coast and Seattle in recent years.
• Light-metro, essentially a fully grade separated version of light rail, but can also be with more metro styling/trains and potentially driverless. Examples of this include Vancouver’s SkyTrain and the Copenhagen Metro. Wikipedia sometimes calls these “Medium capacity rail systems“.

If we think about the City Centre to Mangere corridor, what’s notable is that for the most part, about 65% of the route, the part from Dominion Rd to the Airport, is same regardless of which mode is chosen, being off-road and grade separated. That leaves the main difference between these two solutions the section along Dominion Rd. So that’s where I’ll focus this comparison.

Route/Separation/Reliability

Light Rail

The light rail solution for Dominion Rd would be to have tracks in dedicated lanes that are separated from general traffic. This could be by way of kerbs or larger medians. Traffic would not be able to drive along the tracks at all, unlike bus lanes which have many exceptions, and this priority would extend through intersections to improve reliability. At intersections signal pre-emption would mean vehicles will not often have to stop, giving light rail vehicles a continuous run.

Light Metro

With the need to be entirely grade separated, light metro would need to be either elevated, underground or at least totally fenced off on both sides. Building an elevated line or a ‘Berlin Wall’ at ground level would seem near impossible to get public support over, and so it would mean the line would almost certainly need to be underground the entire route. At the city end of the line, the route would likely need to head under Symonds St and hook around under Wellesley in order to set it up for expansion to the North Shore. Being fully grade separated it would make the line highly reliable but at significantly more cost than a surface solution. We know from overseas that fully tunnel metro lines cost around ten times as much per kilometre than tracks at ground level.

Building an elevated line down Dominion Rd seems unlikely to get public support meaning an underground line would be needed for a metro solution

Stations

Light Rail

A big benefit to a light rail solution is stations are much easier, at their most basic they just need kerbs and shelters. This helps keep them highly accessible and affordable as there are no need for lifts and elevators etc. like with underground or overhead stations. A light rail station can be built more or less in the ideal spot at street level, while an elevated or underground station is often located wherever it’s feasible to build.  For a route like Dominion Rd this means extra stations can easily expand coverage without having a significant impact on budget or travel times. One potential benefit of surface solutions is it also makes it more likely we’ll see other streetscape upgrades.

Light Metro

My understanding is the biggest and most complex and most costly aspects of the City Rail Link are not the tunnels but the stations and the same would apply to a light metro solution. This means for any metro solution we would want to limit the number of stations. Fewer stations does help provide a faster service but that comes at the expense of coverage meaning we also need more intensification around the remaining stations to get the same outcome.

To highlight the difference, this is an image I made for a previous post looking at 400-800m walking catchment. The image on the left is a metro type solution while the image on the right is a what we might see with light rail. As you can see, a metro type solution would leave some big gaps, particularly between Balmoral and Mt Roskill.

What this means is that if we were to build a grade separated option with fewer stations, we’d likely still need to run buses of some form on Dominion Rd to provide accessibility.

Speed

The level of grade separation and the number of stations all contribute to just how fast services would be but in reality the difference probably isn’t as much as people would think.

Light Rail

A light rail route from about the Civic through to the Mt Roskill shops is about 6.3km in length. Based on examples overseas, we should expect services to be able to reliably do this trip in about 18 minutes, even with Queen St having a 30km/h speed limit. At peak times that’s about 5 minutes faster than even the express buses today and about 15 minutes faster than regular buses.

Light Metro

The light metro route works out slightly longer at 6.9km due to needing to get under Wellesley St. However, the fewer stations and no street speed limits this does make for a faster service. Based on overseas examples and some of my own calculations, this suggests the trips is likely achievable in about 12 minutes, so about 6 minutes faster than the light rail option but you probably need to add at least 30 seconds on each end to get between the surface to the platform, so let’s say a 5 minute difference.

Cost

Cost is perhaps one of the hardest things to quantify as we don’t have any local examples to compare to and also the construction industry is busy both here and overseas.

Light Rail

Being on the surface makes for much cheaper, but still expensive, construction. Sydney’s new light rail cost about A$2.2 billion for 12km of tracks, trains and depot. That’s about $180 million per km but did include a lot of challenging services to move and streetscape upgrades in the city centre. Other systems, such as those in the Gold Coast and Canberra have come in much cheaper with Canberra’s 12km line coming in at A$707 million or about $59 million per km.

For the purposes of this let’s assume the mid-point of this, about $130 million per km. That would put this section of Dominion Rd at about $820 million.

Light Metro

Underground tunnels and stations are incredibly expensive, as we’re seeing with the CRL. In the city centre the costs are likely to be similar to the CRL but could well end up cheaper for other parts of the route. As an overseas example, Vancouver’s Broadway Subway extension is costing about NZ$600 million per km. Even at that price this section would cost over $4 billion but likely would be much more.

I could write more but the post is already long enough.

If this next phase is to be a success, I think it’s going to be important to have a conversation on these trade-offs (and the rest) with the public. They will also need to be clear about how the corridor will fit in with the wider network. We don’t need to solve all he issues for the next 100-years. This could mean we build a light rail line now but add other lines, or even a separate metro line in the future – and doing that doesn’t take away from what is done with Dominion Rd.

For me, I’m not sure that saving 5 minutes and having a smaller coverage area is worth at least an extra $3 billion, likely more. We’ll always need some form of PT on the surface of Dominion Rd and so light rail seems to cover both roles the best. But a metro solution, probably on a different corridor, may be an option as part of a wider and longer term vision.

Finally a quote from Grant Robertson on all of this from the event about a week ago.

Any city that requires a retrofit of itself while people are living in it goes through frustrations and I do want to outwardly acknowledge that. If we could go back in time and we could all embrace Mayor Robbie’s ideas from the mid-1960’s onwards we perhaps wouldn’t be having some of the conversations we’re having today about transport. As a result, we’re having to retrofit the fact we didn’t. Obviously I wasn’t around and Phil Goff was only a long haired student protesting at that point so even he can’t be blamed for not taking up Mayor Robbies ideas.

But we all of us now have to accept we’re retrofitting the city and that means disruption through, as you’re seeing now like the City Rail Link, but it’s also why when we come to projects like light rail or mass transit, I don’t buy the argument that was advanced by some people that “10 or 15 years of road cones” is something that can actually in some senses be avoided. The city needs to be future proofed. The old saying is the best time to plant a tree was 30 years ago and the second best time is today. We didn’t plant it in the case of Auckland Transport all that time ago and we need to do it now.

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