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.

 
 
 
 

Here’s everything we learned from the DfT’s database of daily road use statistics

Lovell Street, York: popular with cyclists. Image: Google.

The Department for Transport (DfT) has released averages of daily road use over 22,700 stretches of road across the country, counting cars and bicycles, motorbikes and mopeds, vans and lorries.

While the broad conclusions shouldn’t surprise anyone – motorways are busy, country roads in the Highlands aren’t – there are some interesting findings hidden in the spreadsheet. What’s more, we can look at where each of these places is using the handy co-ordinates supplied with the data.

Generally, higher population densities means more road users. Image: DfT.

Britain’s bike havens

There are only seven places in Britain where bicycles make up most of the road traffic. But where they do, they tend to outnumber it significantly. The crown goes to Lovell Street, a small street in York, which is pictured above. Probably thanks to its path to the quite lovely Rowntree Park in the south of the city, it sees 96 bikes a day pass through, but just 13 other vehicles.

Further down the list is Cable Street in the East End, best known for a 1936 incident in which Oswald Mosley’s British Union of Fascists were robustly challenged in the marketplace of ideas. Cycle Superhighway 3 runs along the street, which is probably a better explanation than an obscure fascist ritual.

With no shade to the residents of Fairacres Road in Oxford, it’s a street of modest interwar semis with unkempt hedges and a bicycle in every other front garden. It’s located between a bike shop, a set of allotments and sits adjacent to the local convent – you get the feeling Jeremy Corbyn would feel right at home there. It’s not top of the list, but while the other roads tend to attract bikes through pragmatism, this feels more than any other like the stereotype we’d expect.


Death on two wheels

The line between A roads and motorways can be a blurry one, particularly when it comes to the routes into and out of major cities. The A2 from London to Dover, for example, is busier than many strips of motorway outside the capital (and about to jam up completely once we crash out of the EU without a deal).

One key distinction is for cyclists, however – it’s illegal to ride a bicycle on a motorway, but not on most A roads.

Just because you can, doesn’t mean you should, and most cyclists wisely avoid that cascade of cars and lorries heading into Central London – but the data shows that every day, one person insists on making their commute on the A406 from Ilford to Walthamstow by bike, alongside 123,000 other vehicles sharing the 21st busiest strip of road in the UK. If you’re reading this article (and if you’re that into bikes, there’s a good chance) please stop. We’re all very concerned.

 

The road in question. Image: Google.

Londoners love motorbikes (and Scots don’t)

The street with the most motorbike and scooter traffic is Arlington Way in Islington, also one of the places with the most pedal bike traffic: 21 per cent of motorised vehicles travelling down this otherwise unremarkable street behind the Sadler’s Wells Theatre are two-wheeled, which is high, but not that unusual for the capital.

Of the 100 roads with the highest motorbike and scooter use in Britain, 93 are in London, although Wordsworth Avenue in Hartlepool and a stretch of the B6277 in rural County Durham get a confusing shout out. London’s high density, short journeys and thriving courier and food delivery industries account for most of their prevalence, combined with the heavy traffic and high running costs of cars which are more easily avoided with a bike.

High density, easily negotiable geography and dietary variety are the opposite of much of Scotland, so it’s somewhat understandable that 55 of the 100 roads with least motorbikes are located there. The climate won’t help, with wet conditions and winding roads not being conducive to safe riding.

A stretch of the North Coast 500. Image: Google.

But there is one exception – the North Coast 500, a tourist route devised in 2014, is a popular route with bikers, tracing the furthest extremes of the Highlands for 500 miles between Inverness and Ullapool. As a result, the A838, which covers most of the western half of the route, sees roughly 15 per cent of its traffic from motorcyclists.

The busiest counties

The DfT helpfully breaks down its figures by local authority area, allowing us to chart the 209 local areas where daily traffic is heaviest and lightest.

Generally, this tracks closely to population – roads are empty on Orkney and busy in Central London – but it also correlates well with an authority’s propensity for commuting and whether it contains a motorway. Birmingham only comes in middle of the pack in the West Midlands, where the busiest roads are found in Solihull, Warwickshire, Sandwell and Walsall. Leeds comes top in Yorkshire and the Humber, but Sheffield and York are beaten by Wakefield and Rotherham.

Residents of the Scilly Isles see the least activity, with an average of 922 vehicles per day passing through any given road. Since the largest island, St. Mary’s, can be crossed on foot in under an hour, it doesn’t seem like the sort of place that would support a daily commute. On the other hand Slough, containing the M4, a chunk of the M25, and a significant slice of commuter belt, tops the list by playing host to an average of 38,000 vehicles per road, per day.