The cost of space (for cars)

Earlier this month, urban policy researcher Todd Litman published a useful summary of some of his new research into the cost of sprawl:

Our analysis indicates that by increasing the distances between homes, businesses, services and jobs, sprawl raises the cost of providing infrastructure and public services by 10-40 percent. Using real world data about these costs, we calculate that the most sprawled quintile cities spend on average $750 annually per capita on public infrastructure, 50 percent more than the $500 in the smartest growth quintile cities. Similarly, sprawl typically increases per capita automobile ownership and use by 20-50 percent, and reduces walking, cycling and public transit use by 40-80 percent, compared with smart growth communities. The increased automobile travel increases direct transportation costs to users, such as vehicle and fuel expenditures, and external costs, such as the costs of building and maintaining roads and parking facilities, congestion, accident risk and pollution emissions.

[…]

We estimate that in total, sprawl costs the American economy more than $1 trillion annually, or more than $3,000 per capita, and that Americans living in sprawled communities directly bear $625 billion in extra costs, and impose more than $400 billion in additional external costs. This is economically inefficient and unfair: it wastes valuable resources and imposes costs on people who do not benefit from sprawl.

These findings should not be particularly surprising to regular readers of Transportblog – or, indeed, to anyone with an elementary understanding of geometry. (Serving dispersed suburbs with network infrastructure is more expensive.) But the magnitude of the costs is impressive.

I was particularly struck by the following chart, which illustrates the amount of space required for various different transport modes. Litman estimates that each automobile requires a total of 80 to 240 square metres, mostly for parking. By comparison, walking, cycling, and public transport require less than 20 square metres per passenger:

As I’ve written before, space is expensive in cities, which means that we must use it efficiently. Moreover, the cost of space for cars is rising rapidly, while demand for driving is levelling off. In this situation, devoting more space to roads and parking – or preventing the re-use of road space and parking lots for other purposes – may represent a significant misallocation of resources:

So, we might ask: How much space have we misallocated as a result of our bias towards building roads rather than public transport and cycling options? And what else could we be doing with this space instead?

First, some data. As we tend to build road networks for peak demands, they tend to have spare capacity during the middle of the day and evenings. Consequently, I’m going to focus on trips taken in the morning peak. This is a conservative view on the space required for a car-based transport system, as cars used during off-peak times still require lots of parking.

According to modelling results reported by Wallis and Lupton (2013), in 2006 there were around 450,000 vehicle trips taken during the morning peak. (See Table 4.1 in their report.) Most of these are trips in single-occupant vehicles. How much space do we need to accommodate all these vehicles?

Based on Litman’s figures, travelling by car requires an average of 150 square metres of space – around 40 square metres of roads per car when moving and 110 square metres for parking. This implies that the 450,000 vehicles moving around during the morning peak occupy 67.5 square kilometres of space, including (at minimum) 18 square kilometres of roads.

That’s a lot of land. Urban Auckland covers a total area of around 544 square kilometres, which suggests that we’re using up around 12.4% of the city’s land area simply to move single-occupant vehicles during the morning peak and warehouse them during the day.

If anything, this is probably an under-estimate of the spatial cost of Auckland’s car-based transport system. A 2013 UN-Habitat report on streets as public spaces and drivers of urban prosperity found that Auckland devotes 14% of its land area to roads alone. Parking is likely to cost us even more space, as this map of Manukau central shows. Everything that’s not coloured in red or green is a carpark or a road:

But regardless of whether we’re dealing with 12% of the city’s land area or 30%, we’re talking about a lot of expensive space devoted to moving or storing cars. Even a modest reduction in the share of people travelling by car in the morning peak would save us a large amount of land.

Let’s say, for example, that we’d invested in better transport choices that enabled 10% of the people in cars to shift to public transport or cycling, which require around 10 square metres of space per person. If we had done so, we would have had an extra 6.3 square kilometres of land that didn’t need to be used for roads and carparks. [6.3km2=45,000 vehicles*(150m2-10m2)]

This is valuable land. Assuming an average land price of around $500 per square metre, it’s worth $3.2 billion. And it could be used for so many more things – housing, businesses, public parks, schools, etc – if it hadn’t been gobbled up by our space-hungry transport system. If it had been developed to the same density as Auckland’s average neighbourhood – around 43 residents per hectare – instead, it could have housed 27,000 people.

In a city that’s struggling to find enough space to house it’s growing population, this amounts to a minor scandal. Since the 1950s, local and central governments have spent lavishly on roads and neglected public transport, walking, and cycling. Those decisions have inadvertently contributed to our housing woes today, as they’ve saddled us with a space-inefficient transport system and a shortage of developable land.

At the moment, local and central governments are looking at ways to get best us out of their own properties. Auckland Council’s setting up Development Auckland to manage and develop its substantial land-ownings. At this year’s Budget, the Government announced a more hastily-developed plan to sell off a significant chunk of the land that it owns in Auckland for development.

Given their interest in the subject, they should also be thinking hard about how to minimise the “opportunity cost” of Auckland’s space-hungry car-based transport system. Investing in public transport and safe walking and cycling can allow us to move more people without gobbling up more valuable land.

What do you think about the spatial cost of our car-based transport system?

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