For such a scientific-sounding word, "density" sure is emotive. Utter it to Nimbys and you might get four-letter expletives. Mention a place like Hong Kong, and eyes glaze over at the thought of mile-high walls of people, packed in like sardines. Density still even brings to mind English cities during the industrial revolution, full of open sewers and cholera.
With so much riding on an ability to create and develop successful cities worldwide, are we making sure they are places we want to live in? That's the real crux – if we don't understand what good density looks like, and what the impact of bad density is on people's long-term health and wellbeing, then we don't have a working basis for current and future developments.
At a spatial level, density is all about the concentration of things in an area. Most local authorities, as well as the ONS, collect information about things they can readily count, such as the density of houses and people. With these two figures, along with other kinds of information, such as brownfield availability and where certain services are located, cities make decisions about how land is used, how it is described and what future uses might be needed.
Described in this way, density shapes how cities look, feel and are experienced. However, it is debatable whether these types of density alone are enough to make decisions. What about the density of rubbish bins? Cars? Cycle lanes?
Getting cities right in terms of density is difficult. For example, scholars advocating a more compact city model suggest that higher overall densities in cities can: support better and cheaper public transport, promote greater energy efficiency in buildings, create more opportunities for mixed-tenure housing, engender more social equality and provide greater control over who people contact. At the same time, high-density cities also lead to: more pedestrian casualties, urban heat island effects and waste; poorer ecosystem quality; loss of privacy and direct sunlight; and reductions in our physical and mental wellbeing.
When we get density wrong, cities may become much more inefficient, as neighbourhoods become dead zones and valuable resources are diverted to solve the problems. So how can cities keep the good bits of density and get rid of the bad bits?
The short answer is: they can't. Cities are messy, complex places with both good and bad bits. But what cities can be is smarter about how they approach the issue.
For example, if high-density cities promote better and cheaper public transport, but induce more urban heat island effects, there should be processes, structures, services and products to maintain low-cost, high-coverage transit that is carbon neutral and works within dense, urban environments.For example, how are Lima and Bogotà doing it? An important question needs to be asked: who is going to be making density-related decisions?
Recent research that I've done with my colleague Professor Rachel Cooper suggests that the people currently making decisions about density, and the things that density affects, are often the wrong people. From a survey of built environment professionals, for example architects, urban designers, town planners, engineers, we found that developers are perceived to be the ones who make many of the density-based decisions in cities, followed by local authority planners and designers. When asked who should be making those decisions, they nominated local authorities, designers, councillors and residents. People also seemed to be making decisions too late in the urban design and planning process, with much decision making occurring during detailed design, rather than earlier, at the conceptual design and development stage.
So, where does that leave us? Perhaps cities with good densities are not necessarily high-density or low-density, but are ones in which more people with a vested interest in the welfare of the urban fabric and urban experience have the opportunity to make or influence decisions. These people also need to be able to make and influence decisions early on and often in the process of designing, developing and maintaining their cities so that innovative and integrative ideas around good density in cities are taken on board and are contextually appropriate. If not, we might all end up living in places like Phoenix, Arizona, or Houston, Texas, which would certainly be an emotive experience.
Dr Christopher Boyko, senior research associate, Lancaster University.
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