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:

AHB traffic volumes and real house prices, 1961-2014

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:

Chivalry Rd Intersection Future

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.

st johns and college road

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?

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19 comments

    1. If I understand the lines correctly, the magenta shows the path, the green shows the extra width required for turning. I think they’ve been left off for that connection because it’s fairly straight and doesn’t add any space requirements to the intersection.

      1. Yep. I figured that after posting but there was is no ability to edit. The intersection would likely be wider if straight ahead traffic was catered for.

        1. Why? They haven’t whited out anything on that side. It would only be wider if they give separate lanes to straight ahead and turning traffic. That’s not a given – it’s a value decision.

  1. Yes unfortunately (and contrary to NZ’s self-purported “clean tree image”) NZ is a very automobile-dependant nation and absurd intersections like this are across the suburban landscape.
    This is thanks to an auto-dependant style of urban form that became popular post-war and it being continued with imports of second hand Japanese cars from the mid 1990’s making it affordable (when it really shouldn’t have been within NZ’s macroeconomy from the early 70’s).

    But it’s going to take decades if it’s ever going to be fixed. There will have to be major changes to the urban design and function of NZ’s suburbs & small towns and the gradual provision of convenient amenities and public transport.

  2. Yes, if we’re choosing between serving people who need housing and serving people who drive, the decision should be overt. Driving is not only space inefficient, as you’ve pointed out, it is also induced by more capacity. Systematically widening each pinch point is systematically inducing more traffic. Whereas if they’d instead systematically improved each intersection by providing:
    – bus stops AT the intersections instead of 200 m or 400 m away, as is often the case even where frequent bus routes cross,
    – safe cycling infrastructure,
    – safe walking infrastructure,
    – space for people using the public realm for recreation,
    – land for small businesses (interest along the route, ie walkability),
    – land for apartments
    then those modes and activities would have increased, and there would be more passive surveillance.

    Yet more reason our traffic planning has reduced the health and richness of our lives.

    Looking forward to the promised transformation, Ellison.

    1. Obviously we’re in dire need of more housing. And the densest housing should be adjacent to major transport corridors. However I don’t think land in the current road corridor should be reallocated to housing, since it becomes a difficult and expensive decision to reverse should we need that land again for alternative modes (BRT, LRT, cycleways etc) or non-transport infrastructure (major pipelines for sewer, stormwater etc).

      So, with the exception of apartments, I think your list of alternative land uses is perfect Heidi.

      1. Thanks. Yes, I’d imagine the situations where apartments would work would be quite limited, so the other suggestions are the more serious ones.

        I am considering housing, though, for parts of the city where passive surveillance is needed and there is an overly wide road corridor. As an emergency response for the housing crisis, tiny houses parked on some of the car infrastructure (carparks and on-street parking most obviously, but perhaps also excessive lanes at intersections) would take away the only justification for spending multiple billions of dollars on greenfields infrastructure, which is that it can be done more quickly. (And I think the answer there is that it’s quicker because the processes are set up for it.)

  3. I don’t think those boundaries were created because someone thought cars needed a lot of space. The Council’s 1940 aerial shows the big triangle already existed when this was still farm land.

    1. Yeah but since they were there someone thought “Oh let’s use as much of this space for vehicles as possible, since nothing else matters!”

      1. Yes weird isn’t it? Someone must have figured there was benefit in having two lanes on each approach. They could have had one lane on each approach and a queue for years, or they could have had no lanes and no road at all. Each of those options would have a different level of usefulness to people. In Newmarket there is an enormous bridge just used for cars. If they removed four lanes they could build dozens of houses up there.

          1. tres threatened, more like. Take a reasonable suggestion and imply that it will ultimately result in all cars being driven into the sea by an angry mob. Extrapolatio ad absurdum

          2. Sorry if I didn’t understand BJ, I thought we were looking for opportunities to turn roads into house sites. But apparently one is silly and the other isn’t. Just as a matter of interest, do you think it would be a good idea to make the College Road intersection smaller if it resulted in buses being held up? Or do you think it will only affect cars somehow and not the 75 service?

  4. The vast swathe of vehicle-devoted land directly outside the mall on St Lukes Road has always baffled me, what with its six total lanes and four large islands. It’s crazy. Morningside Drive is bad as well, with it being nigh on impossible to cross during the day.due to the endless flow of traffic. I’ve missed many a bus due to this. The area is so intimidating for pedestrians, and absolutely nothing has been done to change it.

      1. Peter said, “Simply put, cars use up lots of land, and public transport, walking, and cycling don’t.” Until the dominance by motorcars, the road was used for walking, cycling, playing, socialising, trading, and for horses with carts. Looking at how much value the land would have as housing was simply a way of measuring the land’s value in terms familiar to NZers.

      2. Darn horses taking up all the road! Does seem quite wide. I wonder what other purposes it served, other than horse parking.

        I much prefer roundabouts because in theory they are far safer than traffic lights, but I think we are just crap at building safe roundabouts.

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