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blog: 'Just Right' - achieving the Goldilocks level of urban density

Author: Luke Turner

Here in ITP’s Bristol office, we have been discussing the merits of urban density as a result of Bristol City Council’s current consultation on a new Urban Living Spatial Planning Document (SPD) 'Making successful places at higher densities.  The SPD puts forward the case for using higher density developments, including high rise buildings, to deliver the level of new housing the city needs. Bristol currently doesn’t have many tall buildings and, like many cities across the UK, needs to provide more housing on increasingly scarce land.  With developers chomping at the bit to start building up, the question is: what is the 'just right', or 'Goldilocks', level of urban density? 

What is urban density?

Lets assume in this case we are talking about the number of people living in a particular urban area. This can take many different forms - from the skyscrapers of Manhattan, to rapidly developing cities like Lagos in Nigeria, and the historic centres of many European cities. 

At its best, urban density can help to reduce urban sprawl while supporting higher quality public transport systems... as sustainable transport planners we’re all on-board with that part!  It is easy to understand why Bristol’s Mayor wants to build up, but that might not necessarily solve our problems.

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Do we need castles in the sky?

There are both pros and cons for building tall. Some would argue that tall buildings are awe-inspiring and iconic, and who can argue that Manhattan isn’t an impressive sight?  Others might point detrimentally to the wind turbulence these structures create, or the reflected light melting cars below.  Brent Toderian, formerly Vancouver’s Chief Planner, suggests that tall buildings can offer the best of both worlds if done right

But building tall does not necessarily provide the highest residential density; in New York's skyscrapers, the elevators and stairs take up a huge proportion of the available floor space, and there is lot of expensive exterior cladding for each unit.  So what is the best way of achieving this 'Goldilocks' density?

Human scale

Density doesn’t have to mean high rise. The Urbanist Jan Gehl talks about creating liveable cities through dense neighbourhoods, and the fact that it is the space between buildings which is an important factor in creating the sort of place people want to be. 

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Gehl promotes this through building at human scale - that is a size proportionate to people travelling at human speeds, with space for everyday life to happen and not just to transiently pass through. 

The SPD uses Bristol’s Whapping Wharf as an example of high density new development, and indeed I think this development compares favourably with some of Europe’s best examples of liveable cities such as Copenhagen or the Eixample district in Barcelona. Yes, these are dense urban places, but I believe they are successful precisely because they prioritise people and how they get around the city... not necessarily just because they are densely populated.

I think I know the type of density I would like to go for, but upon writing this article I’ve come to realise that what really matters about density is mobility. How are these people going to get around? Can we expect our public transport, cycle and highway networks to cope with the increased concentrations of peak and off-peak travel demand?  Might everyone just drive if we let them? (Spoiler alert... some research suggests they most likely will!)

How will all these people get around?

Problems with higher levels of urban density can occur when transport and other local facilities aren’t provided. I recently learned about an urban development called Bijlmermeer - a 1960's, Le Corbusier inspired, 'city in the sky' near Amsterdam. What was meant to be a utopia quickly became an bit of a disaster because the planners didn’t quite get the transport infrastructure right. This is an important consideration for Bristol and other UK cities as they look to add high density infill. How will all these people get around?

Bristol's draft SPD talks about the problem of delivering sufficient car parking spaces - should we really be providing any car parking spaces for those without mobility issues?  Bristol has a bit of a traffic problem and traffic congestion often causes blockages to public transport. Allowing new residents the option to drive across the city, from such central locations, could be expected to make matters worse. 

Whilst locating new development adjacent to existing public transport services is warmly welcomed, it is only fair to also question whether Bristol's already-struggling infrastructure can cope with the proposed growth? Significant improvements are needed to local bus and rail networks just to help ensure the city's current population can move freely by motorised modes other than a car.  Similarly, walking and cycling must be prioritised if we are to resolve the widely publicised air quality crisis facing UK cities - including Bristol.

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At ITP we think new developments should plan to change residents' travel habits from day one, by creating walkable and cyclable neighbourhoods that have easy access to bike parking and less than 300m walks to the nearest public transport stops.  Critically, the developments need to be located close to viable walking, cycling and public transport networks if the city is serious about de-congesting the roads and genuinely supporting the growing number of young urbanites who are choosing to adopt car-free lifestyles (or being priced-out of car and home ownership altogether).

What's right for Bristol?

After reading the differing views on how to ‘do density right’ our team reached the conclusion that the most important facilitator of successful higher-density urban development is good sustainable transport connectivity, not vertical height (or super-fast elevators!). 

Making sure people can get around their city independently without needing to use a car feels critical to reducing the extra demands that denser development could place on the city's movement networks. So, how do we achieve this?  Some of our team's initial thoughts include:

  • Thinking big about investments in substantially-improved public transport networks.
  • Delivering better-prioritised strategic walk and cycle networks for human-powered movement. 
  • Pump-priming higher density growth by delivering infrastructure ahead of travel demand.
  • More equitable pricing and taxation structures for private car/public transport/cycle use. 

When these conditions are right then we believe higher density development (whether high-rise or not) can enhance our cities, rather than detract from them.

Bristol City Council’s consultation on the Urban Living SPD closes on 13th April 2018. You can read about it and respond here.


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