Every weekend we dig into the archives. This post by Peter was originally published in June 2015.
Last week, I took a high-level look at the opportunity cost associated with Auckland’s car-centric transport system. Simply put, cars use up lots of land, and public transport, walking, and cycling don’t. At a time when we’re struggling to find space to accommodate the city’s residential and economic growth, this is likely to be increasingly inefficient.
For example, here’s a graph that shows, roughly speaking, the last 50 years of trends in traffic volumes (using the Auckland Harbour Bridge as a proxy) and land values (using national house prices as a proxy). In the last decade or two, demand for intensive land use has far outstripped demand for driving:
However, this isn’t always acknowledged in the activities of transport agencies. As Matt highlighted two weeks ago, Auckland Transport is currently proceeding with a plan to knock down a house (on the bottom left corner of the intersection, shaded in magenta) for an intersection widening project:
A bit earlier, Stu also pointed out an intersection design down in Hamilton that seems quite hazardous to people on foot. Now, there are certainly reasons to redesign – and even widen – intersections. But what worries me is that intersection layout sometimes seem to be on auto-pilot, without any deep consideration of the conflicting values at play or the opportunity costs associated with particular designs.
Take, for example, this intersection at the junction of St Johns Road and College Road in Remuera. It’s large. Very large. Although there’s only a single lane in each direction on the roads in and out of the intersection, it widens to implausible dimensions in the intersection itself. I can only imagine what it’s like to try to cross the intersection on foot.
I asked my friend Lennart, who originally spotted this intersection, to show me how things could be done differently. He quickly sketched up a simplified design – shown in the green and magenta lines – that eliminated the big islands and the split lanes but still left enough room for buses to turn smoothly.
(Caveats: This is not necessarily a better design from a traffic engineering perspective – just a more space-efficient one. As we haven’t looked at traffic volumes, it’s difficult to say whether a signalised intersection or other safety treatments would be required if the slip-lanes were taken out.)
Overall, we found that there would be up to 2,000 square metres of space left over if the intersection was downsized. That’s enough space for three or four reasonably-sized houses on reasonably-sized lots.
Is this expenditure of space worth it? Would it be better to narrow the intersection and sell off the residual land for housing? Possibly. Possibly not. But no matter what the answer is, I hope that those questions are being asked of Auckland’s road designs.
What do you think of the space occupied by our intersections? Good, bad, indifferent?