It’s often said that for public transport to work, you need high residential densities. I don’t remember the exact figures, but I know that there are a few books I have read over the years that have gone to the level of calculating the densities required for different levels of public transport service – ie. what you’d need for a half-hourly bus service, a 15 minute frequency bus service, a railway line and so forth. It’s certainly true that the cities around the world which have the best public transport systems tend to also be those with some of the highest densities. Hong Kong is a classic example of this – with some of the highest densities found anywhere in the world and a public transport system that caters for well over half the number of trips taken in the city.
However, over the past year or so I have examined the relationship between public transport and population density in a bit more detail, and while the “very high density, very high public transport use” rule still holds, when you start comparing cities in New Zealand, Australia, Canada and the USA with each other the whole matter gets rather more complicated. For example, Brisbane and Perth have significantly higher levels of public transport use than Auckland; yet at the same time they are also significantly lower density cities than Auckland is. In fact, when one simply looks at the overall population density of Auckland, we’re up there with Sydney and Melbourne – and well above places like Calgary. Yet our public transport usage just doesn’t stack up with those other cities. So what’s going on? Is this a sign that urban density doesn’t really matter that much after all, or is the way that ‘density’ is being measured a bit too simplistic?
I would answer the above question by saying both. Firstly, the somehow ‘magic’ belief that just because you have higher densities public transport will somehow become popular is misguided. Auckland’s population densities since the 1970s have been increasing, particularly on the isthmus which was largely built out by that point, but yet we’ve seen public transport use decline during that time, at least until the last 10 years when we’ve seen that trend reverse. Transportation policy is critically important, and – unfortunately – for the past 50-60 years Auckland’s transportation policies have been almost staggeringly roads-centric. Simply banging on an urban limit and encouraging the subdivision and infill of large sections has not been able to overcome such strongly pro-roads transport policies.
Secondly, and perhaps more importantly, measuring density in its simplest way – the whole population of Auckland divided by the area of the city, is misleading in terms of really getting some idea of the suitability of the city for public transport. If one were to, for example, compare Auckland with Vancouver, you would find that the densities in Vancouver are far more ‘lumpy’, with high concentrations around railway stations and the CBD, but with lower densities in other areas. By contrast, in Auckland we generally see (with some exceptions) a relatively uniform density across the whole city. Particularly in newer built areas, there’s a staggering amount of uniformly sized 400-500 square metre sections – generally with a large standalone house in the middle of them. This uniform density tends not to lend itself well to public transport, which works best when there are significant development nodes around train stations, or intensive corridors around high-frequency bus routes. Many of the plans and strategies that Auckland has come up with over the past decade look to remedy this issue, but they are turning out to be extremely slow in actually changing things.
Much is made of how land-use planning influences transport use and options, but perhaps what is a bit ignored is how this process also works in reverse – that transport policy, projects and so forth can enormously influence development patterns. I do have to wonder whether it was planning rules that created Auckland’s relatively uniform density (and thus reinforced its auto-dependency), or whether it was the transportation policies that created the auto-dependency first – and that auto-dependency created our relatively uniform density. This would be largely because there was no real motivation to cluster development around the train stations, because the service was so poor, or bus routes – because there were no bus lanes and the trams had been ripped out in the 1950s.
The relevance of exploring how density, land-use patterns and transportation policies interact is when we look at which transport projects we may be choosing to prioritise. As I have explained in a number of previous posts [link to post about how to prioritise transport projects] accurately working out which project is needed the most, or which will have the best outcomes, is very complicated and difficult. Perhaps a tool that we’re ignoring in that process is looking at which projects will create the land-use outcomes that we’re actually seeking. For example, if we were to build the CBD rail tunnel it is most likely that development in the CBD and in suburbs serviced by the rail network (such as New Lynn) would be more likely to encourage development and intensification. On the other hand, if we are to prioritise projects such as the Puhoi-Wellsford motorway then the land-use outcomes most likely to occur would be further development to the north of Puhoi – taking advantage of the shorter travel times between places like Warkworth, and Auckland.
When one thinks about transport projects in this manner, a lot of the haze about which project makes more sense seems to clear. A lot of work has gone into figuring out where it makes most sense for Auckland to grow, so perhaps when looking at what transport projects we should be focusing on delivering, closer inspection needs to be made into which projects deliver the land-use outcomes that we’re most after. This would also enable transport projects to be more ‘forward-looking’, as the current ‘cost benefit analysis’ approach is very much fixated upon a ‘what’s the biggest problem in need of fixing’ way of thinking, rather than a ‘what are we really going to need in ten, twenty or thirty years?’ approach.