Polycentric Cities and Sustainable Development

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Research mapping the density and function of commercial activities in Greater London, then exploring relationships with travel patterns. Part of my PhD research at CASA UCL. Presented at Regional Science UK and Ireland Section 2009.

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Polycentric Cities and Sustainable Development

  1. 1. Polycentric Cities and Sustainable Development:<br />A Multi-Scale GIS Approach to Analysing Urban Form<br />Duncan Alexander Smith<br />Regional Science 4th Sept 2009.<br />
  2. 2. Polycentric Cities and Sustainable Development:A Multi-Scale GIS Approach to Analysing Urban Form<br />Urban Theory of Polycentric Cities-<br />What is driving polycentric structures? How can we measure this?<br />Mapping Employment Geography-<br />Techniques for the detailed mapping of economic activity and mix-of-uses applied to Greater London.<br />Polycentricity and Commuting Efficiency-<br />Are polycentric structures efficient in environmental and economic terms? Analysis applied to the South East.<br />
  3. 3. Polycentric Cities- Evolution of Urban Form<br />Globalisation and Information economy; gentrification, cultural/retail/tourism synergy.<br />Airport attraction, manufacturing, large scale retail/leisure.<br />Cities Enable Agglomeration<br />Economic agglomeration allows specialisation, competition, share labour/info, economies of scale. Socially enables cultural development, ‘urban buzz’.<br />Traditionally Monocentric<br />Pre-industrial cities high density, maximise agglomeration. Public transport networks in 19th century cities reinforce monocentric structure.<br />Polycentric Cities<br />Rise of automobile, economic growth and restructuring. New urban forms evolve with multiple centres- multi-nucleated city (Harris and Ulman), 100 mile city (Sudjic), polycentric city (Gordon)…<br />Monocentric and polycentric trends overlapping with multiple centres with competitive advantages for particular activities.<br />
  4. 4. Polycentric Cities and Travel Sustainability<br />Urban Task Force Key Diagram (1999)<br />Monocentric Characteristics<br />Monocentric structure supports public transport, but increases work-living separation and congestion with tidal commuting.<br />Polycentric Advantages?<br />Polycentric structures disperse employment closer to population, less congested outskirts. But often poor public transport access and produce car based orbital travel. <br />Planning Policy<br />Planners try to integrate with ‘concentrated dispersion’ policies. Is it working?<br />Urban form and employment data integrated with travel patterns evidence base for this debate.<br />
  5. 5. Spatial Analysis of Polycentric Cities<br />To identify polycentric structures and consider travel efficiency, what data and analysis is needed?<br />Employment Data<br />Firstly need to understand spatial structure of economic activity. Employment data key measure. Desirable features for polycentric city analysis-<br /><ul><li>Fine scale to identify intra-urban employment centres.
  6. 6. Regional extent, as often polycentric urban regions.
  7. 7. Measure specialisation of employment sectors and functions.
  8. 8. Consider physical factors thought to encourage sustainable travel- density and mix of uses.</li></ul>Commuting Analysis<br />Linking employment structure to commuting efficiency analysis-<br /><ul><li>Commuting data spatially referenced to destination i.e. employment location.
  9. 9. Accessibility analysis of commuting data- distance, time, generalised cost.</li></li></ul><li>New Techniques is Urban Analysis<br />Aggregate Methods Base of Human Geography<br />Quickly identify large scale patterns, compliments zonal socio-economic data. Often not sufficiently fine scale for intra-urban analysis and can lack sectoral disaggregation.<br />Real Estate Data<br />Very fine scale, spatially reference with address matching. Using Valuation Office data, spatially aggregating for analysing entire city.<br />Commuting Data<br /> By spatially referencing to destinations and combining with employment census variables can provide data on employment sectors at relatively small zonal scales.<br />
  10. 10. Mapping Urban Density and Function- Valuation Office Data<br />Commercial Property Data<br />Valuation Office data includes-<br /><ul><li>Function of activities
  11. 11. Floor-space.
  12. 12. Rateable Value- floor-space multiplied by a rent factor indicative of quality of property. </li></ul>Relationships with Employment<br />Strong relationships between rateable value and employment, but variations in intensity between functions (e.g. industrial vs. office). <br />Methodology<br />Classify data into functional groups- office, retail, industrial, local services…<br />Address match data.<br />Aggregate into 500m grid for visualisation across Greater London.<br />
  13. 13. Density of Office Rateable Value for Greater London 2005<br />
  14. 14. Density of Retail Rateable Value for Greater London 2005<br />
  15. 15. Office & Retail Rateable Value for Greater London 2005<br />
  16. 16. Office and Retail Density Analysis<br />Analysis Results-<br /><ul><li> City Centre Dominance: Dominance of central agglomeration, merging into inner city. Diverse mix of uses.
  17. 17. Tertiary Centres: Canary Wharf grown rapidly. Similar trends to West.
  18. 18. Outer Centres: Significant for retail, but lack major office agglomerations. Struggling to compete.
  19. 19. Edge City: Mono-functional office growth around Heathrow.</li></ul>Future work- time series, land-use model input<br />Useful visualisation for communicating employment structure. Understand employment structure in relation to commuting-<br /><ul><li>Need to measure specialisation of employment.
  20. 20. Analysis of travel efficiency.</li></li></ul><li>Employment Specialisation<br />Investigate economic functions of employment centres. Specialisation measures also needed to understand commuting as longer distance travel for higher paid more specialised jobs.<br />Sectoral Specialisation<br />Clusters of specialised activity. For this analysis need cross-sector specialisation measure.<br />Functional Specialisation<br />Want to differentiate between front-office and back-office activities.<br />Use census data on occupational classes.<br />
  21. 21. Commuting Carbon Emissions Measure<br />Mode Split Analysis<br />Simple centre-suburbs split.<br />Ignoring distance travelled and energy used in public transport journeys.<br />Features Needed<br />Destination based to relate to employment, integrate distance and mode data.<br />Composite Carbon Measure<br />Possible to estimate average carbon per journey, using average carbon emissions per unit distance.<br />(distance currently Euclidean, missing congestion)<br />Walking and Cycling!<br />
  22. 22. Travel and Sustainability- Outer London Diversity<br />Edge City<br />No longer centre-suburbs split, but edge city vs. rest split. Likely link to office parks identified earlier.<br />Centre Sustainable?<br />Central London public transport dominated but long distance.<br />Outer Contrasts<br />Outer Centres close live-work relationships, so efficient. Sharp contrasts to western corridor.<br />South East<br />Edge city extends west with similar commuting. Reading possible exception. Specialised jobs likely influencing commuting.<br />
  23. 23. Employment Specialisation and Travel Patterns<br />Economic Specialisation Proxy<br />Proportion of jobs in top three categories for proxy.<br />East-West Split<br />Much lower specialisation in East London.<br />Western Wedge<br />Generally high productivity, comparable to Central London, not back office.<br />Outer Town Centres<br />Most Outer Centres lower productivity jobs.<br />Specialisation and sustainability tension.<br />
  24. 24. Conclusions<br />Usefulness of Fine Scale Real Estate & Commuting Analysis<br />Integration of socio-economic and built environment data opens new research possibilities.<br />Monocentric-Polycentric Debate in London<br />Mixed support for critique of mono-centric structure, Central London reasonably efficient and extremely specialised. Outer London contrast between efficient town centres and Edge City.<br />Challenge to Redirect Edge City Growth<br />Ideally want West London success mimicked in other Outer Centres, difficult to overcome market preferences. Within Western Wedge focus on mixed use and larger settlements. <br />Further Work-<br /><ul><li> Include travel time and congestion in commuting indicators.
  25. 25. Social and demographic considerations: Demographic considerations (family orientated environments, housing market divisions) big influence on live/work relationships.
  26. 26. Rent data: economic analysis of built environment links.
  27. 27. Temporal Analysis: Density data fixed in time. Have access to London Development Database for new completions and permissions, one route.</li></li></ul><li>Next Steps- Networks and Congestion<br />Commuting Time Analysis<br />Main weakness in commuting analysis missing time data. Travel costs driving behaviour are time and money, not carbon emissions. Need time not distance. In London need to understand congestion.<br />City centre congestion encouraging decentralised growth.<br />Congestion Effects in Carbon Emissions<br />Congestion also has knock on effects on carbon emissions, leading to slower, longer distance journeys.<br />ITIS GPS Data Analysis<br />Working with new data set from TfL to understand road congestion, and allow the calculation of commuting time and more accurate carbon emission estimates.<br />Example of ITIS Network Data<br />
  28. 28. Thank you for listening! Welcome comments and questions.<br />Contact Email: duncan.a.smith@ucl.ac.uk<br />Data providers for this research:<br />Greater London Authority<br />Ordnance Survey<br />Valuation Office<br />Infoterra<br />
  29. 29. References<br />Alexander, C. (1974). A city is not a tree.<br />Alonso, W. (1964). Location and land use.<br />Batty, M. (2000). &quot;The new urban geography of the third dimension.&quot; Environment and Planning B: Planning and Design27: 483-484.<br />Batty, M. (2007). &quot;The creative destruction of cities.&quot; Environment and planning. C, Government & policy34(1): 2.<br />Breheny,M.,Gordon,I.,Archer,S.(1998), ‘Building densities and sustainable cities’, Engineering and Physical Sciences Research Council (EPSRC), Sustainable Cities Programme, Project Outline No. 5, June 1998.<br />Burton, E. (2002), Measuring urban compactness in UK towns and cities, Environment and Planning B: Planning and Design 2002, 29, pp 219 – 250.<br />Urban Task Force (1999). Towards An Urban Renaissance, E & FN Spon.<br />Foster (1999), Docklands: Cultures in Conflict, Worlds in Collision, UCL Press, London.<br />Jane Jacobs (1961) The Death and Life of Great American Cities New York: Vintage Books (NA 9108.J17); <br />Jenks, M, Burton, E., Williams, K. (2000) The Compact City: A Sustainable Urban Form?, (Spon. London).<br />GORDON, P. and RICHARDSON, H. (1996) Beyond polycentricity: the dispersed metropolis, LosAngeles, 1970-1990, Journal of the American Planning Association, 62, pp. 289±295.<br />Greater London Authority (2004), The London Plan: Spatial Development Strategy for London, GLA.<br />Greater London Authority (2006), London Office Policy Review 2006, GLA.<br />Hall, P. (2003). &quot;The End of the City? The Report of My Death was an Exaggeration.&quot; City7(2): 141.<br />Longley, P. A. (2002). &quot;Geographical Information Systems: will developments in urban remote sensing and GIS lead to&apos;better&apos;urban geography?&quot; Progress in human geography26(2): 231.<br />Newman & Kenworthy (1989), Overcoming Automobile Dependence, Island Press, Washington.<br />Sherlock, H. (1991). Cities are good for us.<br />Talen, E. (2003). &quot;Measuring Urbanism: Issues in Smart Growth Research.&quot; Journal of Urban Design8(3): 303.<br />
  30. 30. Relevance of Built Environment Analysis<br />Urban Form reflects and shapes urban processes. Integral to urban activities.<br />Geography of Urban Form Relevant to-<br /><ul><li>Economic activity:urban growth and development, land use and efficiency of travel.
  31. 31. Social geography:housing patterns, gentrification, access to services, property market.
  32. 32. Urban Sustainability:transportation patterns linked to structure, energy use in buildings.
  33. 33. Urban policy and planning: enhance evidence base on land use and built environment.</li></li></ul><li>Economic Specialisation and Sustainability<br />Economic Specialisation Proxy<br />Use census data on employment categories. Sum the top three categories for proxy.<br />Outer London Mix<br />Most Outer Centres lower productivity jobs. Many Edge City high productivity, not back office. Specialisation and sustainability tension.<br />Combine Economic Specialisation and Sustainability<br />Best combination in West London centres. East fares much worse.<br />Market favoured West, why? Image and closer to workforce? Also local scale factors?<br />
  34. 34. Data Models for Integrating Between Scales<br />Need methods to integrate fine scale data, and aggregate at multiple scales respecting urban form.<br />Address Based Geography<br />Spatial address infrastructure greatly improved (OS AL2). Can be used to geo-code any address based data.<br />Aggregation Methods<br /><ul><li> Block Based Aggregation- Buildings between streets.
  35. 35. Street Based Aggregation- Streets themselves are units used.
  36. 36. Larger Scale Grid- City wide representation, try to reduce MAUP errors </li></li></ul><li>Office & Retail Floor-spacefor Greater London 2005<br />
  37. 37. Introduction to Urban Trends in Greater London<br />Monocentric Structure<br />London traditionally concentrated jobs in city centre with radial transport links to suburbs.<br />Central Expansion in Boom Years<br />Massive employment growth and immigration led population growth, particularly over last ten years. Policy directed growth to centre, global business services. Radial transport enhanced.<br />Outer London Contrasts<br />Significant growth around Heathrow and in ‘Western Wedge’, while traditional Outer Centres generally struggling.<br />

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