Urban density matters – but what does it actually mean?

Shove up: London's Oxford Street, looking crowded. Image: Getty.

In debates about urban density we often find comments about buildings being too tall or not tall enough, about too many people in a neighbourhood or too few, about streets and buildings being overcrowded or empty.

We are told that Melbourne is building at four times the density of Hong Kong, or that density is good and will make us happy.

But as these debates over density in cities continue, what is most often missing is any clear understanding of what people mean when they use the word “density”.

Is it the volume or height of buildings? Or is it the numbers of people? One person’s high density may be another’s sprawl; the same tall building may be experienced as oppressive or exhilarating; a “good crowd” for one can be “overcrowded” for another. One is reminded of Humpty Dumpty’s logic in Through the Looking Glass:

When I use a word it means just what I choose it to mean – neither more nor less.

What such debate most needs is greater density literacy.

Density is a concept borrowed from physics where the meaning is clear – mass divided by volume. Yet when transferred to the city, nothing is so simple.

Are we talking about buildings or people?

First, we need to clarify whether we are talking about concentrations of people or of buildings. If we take population densities first, these are generally measured as residents per hectare based on census data.

But we also need to distinguish between “internal” and “external” densities – the numbers of people in a room or apartment versus those in an urban precinct. If you look at new high-rise housing in the evening, you can find many apartments unoccupied. At the other extreme, internal crowding largely defines a slum. Building density does not mean population density.

Building density does not necessarily mean population density, an example being low-occupancy housing in Melbourne Docklands. Image: Kim Dovey/author provided.

Population densities cannot be based on residents alone, since the numbers of people in a given neighbourhood at a given time include those who work there or are visiting. In a mixed-use neighbourhood, residents may be a small proportion of the population density.

There are also population density rhythms, as people move from place to place throughout the day and week. The same urban precinct can be densely populated during work hours and empty on weekends. Population density is not only the number of residents but fluctuates over time and with functional mix.

And how do you measure building density?

When we shift attention to building densities, we soon encounter some unavoidable jargon. The most common measure of building density is the “floor area ratio” (known variously as FAR, FSI, FSR and plot ratio) – the ratio of floor area to land area. This is the most widely used measure for limiting the bulk of development on any given plot.

However, it does not control the building height, “footprint” (the area occupied by the building) or “coverage” (the proportion of land covered by buildings). Thus it is quite possible to build high-rise low-density (with very low coverage or small footprints) or low-rise high-density (with high coverage or large footprints).

Most high-rise public housing from the 1960s and 70s is roughly the same FAR as the low-rise housing that was demolished to build it.

Building height is not a measure of density, although sometimes the two align. Confusions here abound; press reports (such as here and here) regularly equate FAR with height control.

Areas of different heights but similar building density in Fitzroy, Melbourne. Image: Kim Dovey/Google Earth.

Another common measure of density is dwellings per hectare. This is often used as a means of assessing population and building densities at the same time. But it does neither, unless we know the size of dwellings and of households. Thus dwellings per hectare is a very blunt measure of density, although a useful proxy for comparing housing projects.

Then there is the distinction between gross and net densities. Urban planning controls are focused on the net density on a particular site – yet such measures are of little use in understanding how cities work, because they do not include the public space of streets and parks.

The gross density is always lower than net density and it is the one that matters in debates over urban density. While we might be packed in on a particular site, the street network of a car-based city tends to keep us apart. Net density is not an effective measure of urban density.

As we measure densities of people or buildings at larger scales, we also incorporate water bodies, freeways and unbuildable sites, so the average density diminishes. Where one draws the boundary is a crucial decision in measuring urban density, or in getting the answer one wants.

Even urbanists such as Paul Mees can be guilty of this when using broad metropolitan density measures to advocate for public transport at suburban densities. Elizabeth Farrelly, a vocal proponent of higher density, compares it to the thread-count of luxury sheets (her minimum is 1,000), yet her only measure for urban density is “dwellings per hectare” – whatever the scale, net or gross.

Here we encounter the politics of density literacy and return to the logic of Humpty Dumpty:

The question is which is to be master – that’s all.

There is no single scale at which to measure urban density, but the larger the scale, the lower the density. The best approach is to understand density as multi-scalar: for any location there is an internal density, a net density, a walkable density and a metropolitan density.

High density is no guarantee of urban buzz

Finally, there is the question of streetlife density – of people in public space, of crowds and crowding. Here the complexities multiply. While we can measure the outcomes in pedestrians per minute or per square metre, we are far from understanding the ways in which streetlife is geared to building and population densities.

These connections depend at least on numbers of jobs and visitors, functional mix, car dependency, access networks and walkability. Yet this is where density delivers its greatest benefits in social and economic encounters – what we often call the urban “buzz” or “intensity” – along with disbenefits such as congestion.

Density without intensity in the car-dependent city – in this case, Tampa, Florida. Image: Author provided.

In Australian cities we have become quite good at generating high density without intensity. Think of car-dominated high-rise districts where few people use the street. Yet we also have good inner-city examples of intensity without high density.

For many people, density has become a negative word. Those who want more of it often use other words and phrases: the “compact city”, “urban intensification”, “transit-oriented development” and the “30-minute city”.

This can be useful language but the question of what it means remains. The challenge is to raise the standard of urban density literacy – not to make density mean one thing but, as Alice might put it, to understand the ways it is made to mean so many different things.The Conversation

Kim Dovey is professor of architecture and urban design, and Elek Pafka a research fellow, at the University of Melbourne.

This article was originally published on The Conversation. Read the original article.

 
 
 
 

Barcelona’s car-free “superblocks” could extend lives. So will they catch on elsewhere?

Barcelona. Image: Getty.

The world’s biggest cities have larger populations and higher economic outputs than some countries. But as they grow in size and complexity, cities are also facing thorny challenges that threaten the health and happiness of residents. Congestion, pollution and a lack of community spaces have become major drags on people’s aspirations and experiences of urban living.

In response, cities must manage their resources and priorities to create sustainable places for visitors and residents, and foster innovation and growth. Enter Barcelona – the capital of Catalonia, in Spain – where a bold stroke of urban planning first introduced “superblocks” in 2016.

Image: ISGlobal/FAL.

Superblocks are neighbourhoods of nine blocks, where traffic is restricted to major roads around the outside, opening up entire groups of streets to pedestrians and cyclists. The aim is to reduce pollution from vehicles, and give residents much-needed relief from noise pollution. They are designed to create more open space for citizens to meet, talk and do activities.


Health and well-being boost

There are currently only six superblocks in operation, including the first, most prominent one in Eixample. Reports suggest that – despite some early push back – the change has been broadly welcomed by residents, and the long-term benefits could be considerable.

A recent study carried out by the Barcelona Institute for Global Health estimates that if, as planned, 503 potential superblocks are realised across the city, journeys by private vehicle would fall by 230,000 a week, as people switch to public transport, walking or cycling.

The research suggests this would significantly improve air quality and noise levels on the car-free streets: ambient levels of nitrogen dioxide (NO₂) would be reduced by a quarter, bringing levels in line with recommendations from the World Health Organisation (WHO).

The plan is also expected to generate significant health benefits for residents. The study estimates that as many as 667 premature deaths from air pollution, noise and heat could be prevented each year. More green spaces will encourage people to get outdoors and lead a more active lifestyle.

This, in turn, helps to reduce obesity and diabetes and ease pressure on health services. The researchers claim that residents of Barcelona could expect to live an extra 200 days thanks to the cumulative health benefits, if the idea is rolled out across the city.

Space to play. Imag: Mosa Moseneke/Unsplash.

There are expected to be benefits to mental health, as well as physical health. Having access to such spaces can stave off loneliness and isolation – especially among elderly residents – as communities form stronger bonds and become more resilient.

Stumbling blocks

It was Salvador Rueda, director of the Urban Ecology Agency of Barcelona, who first championed the introduction of superblocks – and he argues that the idea could be used in any city. Even so, authorities looking to expand the concept in Barcelona or beyond will need to be mindful of some concerns.

Changes like these require capital investment. Even as the car-free streets are transformed with urban furniture and greenery, the remaining major roads will likely have to accommodate heavier traffic.

Nothing comes for free. Image: Zvileve/Flickr/creative commons.

Further investments in local infrastructure – such as improving surrounding roads to deal with more traffic, or installing smart traffic management system – could be required to prevent serious congestion. Then the question remains, how to finance such investments – a higher tax rate is unlikely to be popular.


What’s more, whenever a location becomes more desirable, it leads to an increase in property demand. Higher prices and rent could create pockets of unaffordable neighbourhoods. This may lead to use of properties for investment purposes and possibly, displacement of local residents.

It’s also worth noting that Barcelona is an old and relatively well-planned European city. Different challenges exist in emerging global cities across Asia, Africa and Latin America – and in younger cities in the US and Australia. There is a great deal of variation in scale, population density, urban shape and form, development patterns and institutional frameworks across the cities. Several large cities in the developing world are heavily congested with uncontrolled, unregulated developments and weak regulatory frameworks.

Replicating what’s been done in Barcelona may prove difficult in such places, and will require much greater transformations. But it’s true that the basic principles of superblocks – that value pedestrians, cyclists and high quality public spaces over motor vehicles – can be applied in any city, with some adjustments.

Leading the way

Over the history of human civilisation, great cities have been at the forefront of innovation and social progress. But cities need a robust structure of governance, which is transparent and accountable, to ensure a fair and efficient use of resources. Imposing innovation from the top down, without consultations and buy-in, can go squarely against the idea of free market capitalism, which has been a predominant force for modern economies and can lead push-back from citizens and local businesses.

Citizens must also be willing to change their perspectives and behaviour, to make such initiatives work. This means that “solutions” to urban living like superblocks need to have buy-in from citizens, through continuous engagement with local government officials.

A man speaks at a public consultation on the Eixample superblock in Barcelona. Image: Ajuntament Barcelona/Flickr/creative commons.

Successful urban planning also needs strong leadership with a clear and consistent vision of the future, and a roadmap of how that vision can be delivered. The vision should be co-developed with the citizens and all other stakeholders such as local businesses, private and public organisations. This can ensure that everybody shares ownership and takes responsibility for the success of local initiatives.

There is little doubt that the principles and objectives of superblocks are sound. The idea has the potential to catch on around the world – though it will likely take a unique and specific form in every city.

The Conversation

Anupam Nanda, Professor of Urban Economics and Real Estate, University of Reading.

This article is republished from The Conversation under a Creative Commons license. Read the original article.