A week or so ago I wrote a post about how I think we can make sense out of ferries in the mix of Auckland’s public transport system. I think my key conclusion was that ferries do make sense in certain locations and we should try to take advantage of where they do make sense rather than pushing new routes all the time. Another piece of the public transport jigsaw puzzle is light-rail (or trams). In a number of ways light-rail is actually quite similar to ferries – it has its ardent supporters, it’s pretty expensive (although more in terms of capex while ferries are expensive in terms of opex) yet it also probably makes sense in some circumstances.
Let’s look at those circumstances, firstly by seeing what light-rail’s general advantages and disadvantages are compared to other modes. This is reasonably well summarised in a useful Australian Transport Study that highlights the importance of mode-neutrality when assessing transport projects (in other words, finding the best solution and recognising that all modes have a role to play in the right circumstances):Definitions of different modes is a much debated area, particularly when we’re discussing the “in between” modes of bus rapid transit and light-rail. In my mind there’s effectively a gradation of different types of both technologies – ranging from both buses and trams running in mixed traffic right through to Northern Busway style style bus operations or completed grade separated light-rail.
My general opinion is that in mixed traffic there’s little, if any, advantage to be had from running a tram or light-rail vehicle compared to a bus – as the capacity of the corridor is not determined by the vehicle itself but by the amount of congestion in that lane. At the other end of the scale once we’re talking about full grade separation it seems that light-rail once again doesn’t offer too many advantages over either a busway (which will be a cheaper) or heavy rail (which may be of similar cost but will have much higher capacity). Vancouver Skytrain style light-metro systems are a different issue entirely and have been covered extensively previously in posts that I’ve made.
The most obvious improvement to make as bus patronage grows along a route (or where there’s potential for fairly high bus patronage) is to install a bus lane. By separating the buses from general traffic, the capacity of the lane increases pretty dramatically while reliability and speeds of the bus services also improve a lot. With bus lanes being cheap and quick to implement, in the vast majority of situations probably the most important thing we can do to improve our public transport infrastructure is through extended, new and improved bus lanes.
However bus lanes only suffice up to a certain level of use – something which in many ways was the key finding of the City Centre Future Access Study’s Deficiency Analysis. In terms of buses per hour this is shown below:
Once you start to push the limit of a bus lane the results are fairly ugly:Before I go on to discuss the different options for what to do when a bus lane hits capacity I think it’s worth noting the difference between high frequency bus corridors where a large number of buses converge on a particular street (think Symonds Street or Fanshawe Street) compared to a high frequency bus corridor where frequencies are high of a single route (think Dominion Road north of Mt Roskill). Analysis tends to suggest that simply adding more and more buses in the latter situation hits a limit where it’s not really adding much value anymore as the buses tend to get in each other’s way as they’re all trying to do the same thing but not achieving it particularly well. Of course you can run local/express splits to reduce this problem but once again eventually you’ll hit a wall.
Now moving on, once a basic bus lane no longer has sufficient capacity there are a few options for what you can do about it – and the right solution is likely to depend on the circumstance:
- Upgrade to a higher-quality BRT bus based system. This could involve median bus lanes, a semi-grade separated median busway (like proposed for AMETI) or a full grade separated busway (like the Northern Busway between Akoranga and Constellation).
- Build heavy rail. This could involve a new line completely or extensions to existing lines. It could be underground, at grade or elevated.
- Build light-rail. In this scenario I’m thinking about something that runs at street level in its own lanes but isn’t grade separated at intersections.
What’s probably going to make or break which of the three solutions above is most appropriate will be a number of criteria – the most important in my mind being the level of additional capacity required, the nature of existing infrastructure and the land-use impacts of the option. Oh, and of course the cost. Let’s explore this with a few case studies.
In the case of the City Rail Link project, future growth in public transport demand to the city centre effectively overwhelms the bus network (and the rail network at a later date) requiring something to happen in order to retain high quality access to Auckland’s city centre and around the region. Enhanced bus solutions don’t really work because our existing infrastructure only has a busway to the north whereas railway lines spread out west, east and south – as well as not working due to the capacity required (which would take away too much road space to provide for with buses alone) and also the land-use impact (widened approach roads throughout the isthmus). Light-rail doesn’t really work either as it’s of insufficient capacity and doesn’t integrate with the existing infrastructure.
In the case of the AMETI busway corridor, heavy rail is probably cost-prohibitive due to the need to get across the Tamaki River, while light-rail gets stuck between the need for a lot of feeder buses into Botany and then heavy rail connections at Panmure and Ellerslie at the route’s potential other end. In this situation the busway makes pretty good sense.
In the case of Dominion Road’s long term future, things start to get interesting. Because of the corridor’s significant heritage and character value, large-scale widening for a massively upgraded bus solution is unlikely to ever be feasible. Even widening the existing bus lanes outside the retail centres along the route proved to be impossible to make ‘stack up’. Heavy rail is clearly infeasible at street level or elevated and is almost certainly cost prohibitive underground – so light rail starts to look like it could be worth exploring further. Further potential aspects in favour of light-rail on Dominion Road include its huge potential as a high-intensity mixed-use corridor where amenity of the street environment is important as a shaper of land-use patterns. Plus the route is potentially well anchored at the city end by putting the tracks down Queen Street (probably via Ian McKinnon Drive) and at the southern end by a future rail station/bus hub – so it’s likely to be a single route without any deviations or branches.
Perhaps in summary we can try to distill a clear rationale behind situations where light-rail might make sense for Auckland. I think it’s in situations where demand along a single corridor (rather than where a number of corridors come together) can no longer be efficiently provided for by standard bus lanes and where land-use factors make either enhanced bus priority options or heavy rail infeasible or cost-prohibitive.
In my mind this is a fairly difficult test to pass and I don’t actually think any corridor in Auckland at the moment (perhaps except for Queen Street) would fit the criteria. This will probably annoy some, who want to run trams everywhere and anywhere, including seemingly with mixed traffic along Ponsonby Road. It might annoy others who think that light-rail is an expensive folly which doesn’t make any sense in Auckland. If I annoy both sides of the debate then I’ve probably got it just about right.