Mission 1: In Denmark, 200 people can make a place urban. In Japan it takes 50,000. So how urban is the world?

What makes a place urban?

• Site: the land a settlement is built on, such as a river crossing, a sheltered harbour or a defensible hill.
• Situation: its position relative to other places, routes and resources.
• Function: what it does: administrative, port, industrial, commercial or residential. Functions change over time.
• Land use: how its space is divided between housing, industry, shops and offices, transport and open space.

Who counts as urban?

• Countries define "urban" differently. Population thresholds range from as low as 200 inhabitants in Denmark to 50,000 in Japan.
• World Urbanization Prospects 2025 also applies one rule to every country, the Degree of Urbanisation, endorsed by the UN Statistical Commission for international comparisons:
  • city: at least 50,000 people and at least 1,500 people per km²
  • town: at least 5,000 people and at least 300 people per km²
  • rural area: less densely populated than cities and towns.

One world, two answers

• Adding up countries' own definitions: 58% of the world's people were urban in 2025.
• Using the Degree of Urbanisation: 45% lived in cities and 36% in towns, 81% together.
• The gap arises because many places that meet the town rule are classed as rural by their own countries, especially in Central and Southern Asia and sub-Saharan Africa.
• Exam move: always name the definition behind an urban figure.

The urban hierarchy

• A settlement hierarchy ranks places by size and range of functions: a few large places at the top, many small ones below.
• Cities in 2025 under the UN rule: 33 megacities (10 million or more); 49 of 5–10 million; 429 of 1–5 million; 1,822 of 250,000–1 million; 9,807 under 250,000.
• Megacities rose from 8 in 1975 to 33 in 2025; 19 are in Asia.

Rank-size and primacy

• Rank-size rule: in a country's urban system, the nth-largest city has about 1/n of the largest city's population.
• A primate city is far larger than the rule predicts and dominates its country's urban system.
• The largest cities in 2025: Jakarta (nearly 42 million), Dhaka (almost 37 million) and Tokyo (33 million). Unit 1 studies Dhaka.

Growth process: planned or spontaneous

• Planned growth follows an approved design. Brasília was "created ex nihilo in the centre of the country" and built from 1956 to 1960, planned by Lúcio Costa with buildings by Oscar Niemeyer.
• Shenzhen was established in March 1979 and designated China's first special economic zone in August 1980.
• Spontaneous growth happens without an approved plan, often as informal settlement on vacant or marginal land (Mission 3).

Density varies hugely

• Mumbai was the most densely populated city of 1 million or more in 2025: 27,000 people per km².
• Perth, Australia, was the least dense: fewer than 2,000 per km².
• 21 of the 50 least dense cities of 1 million or more were in the United States.
• Density reflects history, land values, planning and transport (Mission 2).

Mission 2: A square metre of land in Ginza, central Tokyo, is valued at ¥67.1 million. A square metre of housing land in Ome, also in Tokyo, averages ¥98,600. Why the gap?

Land values and bid rent

• Bid-rent theory (Alonso): land users bid for each site according to how much they gain from its accessibility.
• Accessibility is greatest in the central business district (CBD), so land values peak there (the peak land value intersection).
• Shops and offices gain most from being central, so they outbid industry and housing near the centre.
• Values fall with distance, but rise again at secondary centres, stations and main roads.

Tokyo's land value gradient

• Japan's highest commercial land value (1 January 2026): Ginza 4-chome, ¥67.1 million per m², up 10.9% in a year.
• Average residential values per m², 2026: Chiyoda ward ¥3,631,400; Setagaya ward ¥779,900; Hachioji ¥131,300; Ome ¥98,600.
• Even Japan's highest residential value (Akasaka, Minato ward: ¥7.11 million per m²) is about a tenth of Ginza's commercial value.

Where economic activities locate

• Retail: high-order shops and department stores in the CBD; convenience shops in neighbourhoods; large retail parks on cheaper edge-of-city land by main roads.
• Commercial (offices, finance): the CBD and secondary business districts around major stations.
• Industrial: older industry beside rivers, ports and railways; newer industry on cheaper edge-of-city land near ring roads and airports.
• Physical factors (flat, dry, stable land) and planning (zoning) shape all three.

Models of the city

• Concentric zones (Burgess, Chicago): CBD, a zone in transition, then rings of housing rising in status outwards.
• Sectors (Hoyt): wedges along transport routes; high-status housing in one sector, industry along rail or river corridors.
• Multiple nuclei (Harris and Ullman): several centres, such as the CBD, industrial districts and suburban centres.
• Limits: based on US cities of the early and mid-20th century; static; they underplay planning, physical geography and car-based sprawl.

Cities in lower- and middle-income countries

• Griffin and Ford (Latin American city): a CBD with a commercial spine and an elite residential sector running outwards; then a zone of maturity, a zone of in situ accretion and a zone of peripheral squatter settlements, with disamenity sectors on marginal land.
• Exam move: use a model as a yardstick, then show where your city differs and why.

Where people live: residential patterns

• Physical factors: flood-free, well-drained and attractive land (views, higher ground) costs more; steep, flood-prone or polluted land is cheaper.
• Land values: high values near the centre mean dense flats; further out, larger plots and lower densities.
• Ethnicity: people may cluster for support networks, places of worship and shops (voluntary), or because of discrimination and cost (involuntary).
• Planning: zoning, public housing and new towns.

Planning and ethnicity: Singapore

• 76.0% of Singapore's resident population lived in public housing (HDB) flats at end-March 2025.
• In 1989, after "signs that segregation among the races had once again started to take root", the government introduced the Ethnic Integration Policy.
• It sets a maximum share for each ethnic group in every HDB block and neighbourhood; it was "not possible to uproot residents to break up the enclaves".
• The limits are reviewed: in 2010 those for Indians and other minority groups were raised.

Evaluating the policy (AO3)

• Aim: mixed neighbourhoods rather than enclaves, using the state's very large role in housing.
• Trade-off: when a block reaches a group's limit, flat owners there have fewer possible buyers, which follows directly from a quota.
• Transferability: it works because most residents live in state-built flats; it would be far harder where most housing is private.
• Exam move: "To what extent…" answers set the aim against the costs, and say for whom.

Mission 3: In 2011, 1 in 10 people in Mumbai's D ward lived in slums. In M/East ward, more than 3 in 4 did. Why such a gap inside one city?

Poverty, deprivation and informality

• Poverty: too little income to meet basic needs.
• Deprivation: lacking what most people have: income, work, health, education, decent housing, a safe environment. It is multiple when these combine.
• Informal housing: homes without legal title or planning approval, often without services.
• Informal employment: work without legal or social protection, such as a contract, pension or sick pay.

The global picture: slums

• In 2022, 1.12 billion people lived in slums or informal settlements: 24.8% of the urban population, slightly lower than 25% in 2015.
• Over 85% were in three regions: Eastern and South-Eastern Asia (362 million), Central and Southern Asia (334 million) and sub-Saharan Africa (265 million).

Housing costs

• The housing cost burden is the share of household income spent on housing. Its average across 124 countries is 31.0%: 43.5% in sub-Saharan Africa, 21.4% in Northern America and Europe.
• When formal housing costs too much, low-income households turn to informal housing.

Informal work at different stages of development

• Informal jobs as a share of all employment, 2024 (ILO modelled estimates):
  • low-income countries 88.3%; lower-middle 81.5%; upper-middle 50.8%; high income 12.9%
  • world 57.8%.
• Informality falls as income rises but exists at every level of development.

Inside one city: Mumbai

• The Municipal Corporation of Greater Mumbai's ward tables from Census 2011: D ward 34,699 of 346,866 people in slums (10.0%); M/East 685,994 of 807,720 (84.9%).
• Praja Foundation, citing Census 2011, gives 77.5% for M/East. Slum counts depend on who defines and counts slums.
• M/East has sheltered migrants since the 1960s, "as well as those who have been 'resettled' from slums in the inner recesses of the city".
• Land values also matter: formal housing dominates where land is most valuable (Mission 2).

Deprivation in a high-income country: England

• The Index of Multiple Deprivation 2025 ranks 33,755 small areas, averaging about 1,500 residents each, on seven weighted domains:
  • income 22.5%; employment 22.5%; education 13.5%; health 13.5%; crime 9.3%; barriers to housing and services 9.3%; living environment 9.3%.
• The most deprived area is east of Jaywick, Clacton-on-Sea; seven of the ten most deprived are in Blackpool.

Deprivation persists

• Deprivation is concentrated in large conurbations, former heavy-industry and mining areas, coastal towns and parts of east London.
• 82% of the most deprived tenth of areas in 2025 were also in the most deprived tenth in 2019.
• Deprivation is relative: it ranks places against each other, so some area is always "most deprived".

The cycle of deprivation

• Low income → poor housing and diet → poorer health and schooling → fewer qualifications → low-paid or no work → low income for the next generation.
• Area effects reinforce it: weak services, high crime and a poor reputation that deters investment.
• Breaking it needs action at several points at once: jobs, schools, housing and health.

Geographic patterns of crime

• England's index treats crime as part of deprivation: its crime domain measures "the risk of personal and material victimisation at local level".
• Defensible space (Newman): layouts with no clear ownership or natural surveillance, such as some high-rise estates, can be linked with higher crime.
• Common patterns: violence and theft concentrate in city centres at night (the night-time economy) and in some deprived residential areas.
• Maps show crime known to the police, which depends on reporting and policing, not all crime.

Managing violence and deprivation: Glasgow

• In 2005 Strathclyde Police founded a Violence Reduction Unit "in the face of rising homicide rates". By the unit's account, Scotland had 137 homicides that year, 41 of them in Glasgow.
• It uses a public health approach: use data to analyse violence, understand its causes, test what works, then scale it up.
• It works at three levels: tackling the conditions behind violence, intervening early, and responding after violence. It became a national unit in 2006.

Evaluating responses (AO3)

• Area-based schemes target the most deprived places (the index makes this possible), but many deprived people live outside those areas.
• Upgrading informal settlements with services keeps residents in place; the UN calls for slum upgrading to reduce poverty and prevent displacement.
• Evidence: claims of success for the Glasgow unit come mainly from the unit itself; check them against official homicide statistics, and remember that violence falls for many reasons.
• Exam move: say who benefits, at what scale and over what time.

Mission 4: In 1979 Shenzhen was what its government calls "a small backward border town". By 2024 it had 17.98 million residents. Where did they all come from?

Urbanisation and its three engines

• Urbanisation: a rising share of a population living in urban areas. Urban growth: a rising number of urban people.
• Three engines: natural increase in cities, net migration into cities, and reclassification of rural places as urban.
• Centripetal movements flow towards the centre: rural–urban migration, and movement back into inner cities.

Cities, towns and rural areas since 1950

• 1950: 20% of the world's 2.5 billion people lived in cities, and 40% in towns.
• 2025: 45% in cities, 36% in towns and 19% in rural areas, out of 8.2 billion.
• Cities overtook towns as the most common setting in 1996.
• Regions differ (2025): 59% in cities in Northern Africa and Western Asia, 54% in Latin America and the Caribbean, 38% in sub-Saharan Africa.

What drives city growth?

• China's urban share (national definition) rose from 20.6% in 1982 to 63.8% in 2020.
• Of China's urban growth between the 2010 and 2020 censuses, 56% came from rural-to-urban migration, 26% from administrative changes and 18% from natural increase.
• Across many countries, natural increase and reclassification drive most city growth; migration makes a visible contribution in Eastern and South-Eastern Asia and sub-Saharan Africa.

An industrialising city: Shenzhen

• Established March 1979; China's first special economic zone from August 1980.
• 17.98 million permanent residents at the end of 2024; "a young immigrant city", with an average age of 32.5 at the seventh national census.
• Under the UN's density-based rule, the Shenzhen city area had about 13.9 million people in 2025: a different boundary, a different number (Mission 1).
• 2015–2025: China's four megacities, Beijing, Guangzhou, Shanghai and Shenzhen, each grew by more than 0.8% a year, against 0.1% for China's population.

Why migrants move, and what follows

• Push: low farm incomes and few rural jobs. Pull: factory and service jobs, wages and education.
• Migration is selective: mostly young adults. Rural areas face "population ageing and out-migration, as young people move to cities and towns".
• Rapid inflows stretch housing and services; some migrants live in crowded or informal housing (Mission 3).

Back to the inner city: gentrification

• In post-industrial cities, centripetal movement includes gentrification: higher-income households move into, and reinvest in, older low-income inner neighbourhoods.
• Drivers: central service-sector jobs, short commutes, older housing to renovate, new amenities.
• Effects: rising rents and prices, new businesses, and pressure on long-standing lower-income residents.

Evidence from New York

• NYU's Furman Center classed 15 of the 22 neighbourhoods that were low-income in 1990 as gentrifying: their rents rose faster than the median neighbourhood's.
• Average rent change, 1990 to 2010–2014: gentrifying 34.3%; whole city 22.1%; non-gentrifying low-income 13.2%.
• Gentrifying areas saw "a nearly 15.6 percentage point gain in the share" of college-educated adults.
• Examples: Williamsburg/Greenpoint, Central Harlem, Bushwick.

Gentrification: who gains, who loses? (AO3)

• Gains: investment, rising values for owners, new services and tax revenue.
• Losses: rising rents can push out long-term, lower-income renters; local shops change.
• Limits of the evidence: the Furman Center states, "We cannot directly observe if low-income residents are moving out of increasingly high-cost neighborhoods".
• Exam move: separate what the data show (rents, newcomers) from what they cannot show (displacement).

Urban growth to 2050

• Two-thirds of world population growth to 2050 is projected to be in cities, with most of the rest in towns; the rural population should peak in the 2040s.
• India, Nigeria, Pakistan, DR Congo, Egypt, Bangladesh and Ethiopia are projected together to add more than 500 million city residents, over half of the projected 986 million increase.
• Megacities: 33 in 2025 and 37 projected by 2050, as Addis Ababa, Dar es Salaam, Hajipur and Kuala Lumpur pass 10 million. Under the UN's rule a "city" is any contiguous dense area, so the area named after Hajipur (India) already had about 9.9 million people in 2025.
• These are UN projections, not counts.

Changing sizes and structures

• More than 3,000 cities lost population between 2015 and 2025; over a third of them are in China.
• Tokyo is projected to fall from 3rd to 7th largest by 2050, shrinking to about 31 million; Dhaka may become the largest by mid-century.
• The city population of Eastern and South-Eastern Asia could begin to shrink in the 2040s.
• Ageing cities need more housing, care facilities and social support for older people.

Mission 5: Detroit had 1,849,568 people in 1950 and 639,111 in 2020. What emptied the Motor City?

Centrifugal movements

• Centrifugal movements flow outwards from the centre.
• Suburbanisation: people, then shops and offices, move from the inner city to the suburbs: cars and commuter rail, cheaper land, more space, planned estates.
• Counter-urbanisation: people move beyond the urban edge to small towns and rural areas: retirement, quality of life, remote working, long-distance commuting.
• In parts of Europe, city populations have fallen with suburbanisation or counter-urbanisation, and with statistical reclassification of boundaries.

London: in and out at once

• In the year to mid-2025, London had positive natural change and net international inward migration, but "this was more than offset by net outward migration to other areas of the UK".
• As a result, London's population fell by 0.29%, "the first decrease since the year to mid-2021".
• A city can gain from births and international arrivals while losing more residents outwards to the rest of the country.

Deindustrialisation: causes

• Deindustrialisation: a long-term fall in manufacturing jobs and output in a city or region.
• Causes: competition from lower-cost producers abroad (the global shift), automation, firms moving to cheaper sites elsewhere, and economic shocks such as recessions.

Detroit: the Motor City shrinks

• Detroit city's population (US census):
  • 465,766 (1910); 1,849,568 (1950, 5th largest US city); 1,027,974 (1990); 713,777 (2010); 639,111 (2020).
• Most of the loss came early: 821,594 of the 1,210,457 people lost by 2020 had gone by 1990 (computed).
• Job losses began early: historian Thomas Sugrue told the Associated Press that Detroit lost 140,000 jobs between 1947 and 1963, as "the postwar manufacturing boom was largely over by the mid-1950s" (reported by HNN).
• Manufacturing jobs in the Detroit metropolitan area, in the series available, fell from 380,900 (2000) to 174,000 (2009), and were 237,900 in 2025.

Consequences

• Economic: fewer jobs, a shrinking tax base, vacant factories and homes.
• Social: median household income in Detroit (2020–2024, in 2024 dollars) was $39,938, about half the US figure of $80,734 (49.5%, computed). 50.3% of homes were owner-occupied, against 65.2% in the USA.
• Demographic: people who could move for work, often younger and better-paid, tended to leave first (selective out-migration).

The same pattern in England

• England's Index of Multiple Deprivation finds concentrations of deprivation in "areas that have historically had large heavy industry manufacturing and/or mining sectors".
• The effects of deindustrialisation can last for generations through the cycle of deprivation (Mission 3).

Signs of change? (AO3)

• Detroit's estimated population for July 2025 is 649,095, above the 2020 census count.
• Metro manufacturing jobs recovered from 174,000 (2009) to 237,900 (2025), but stay well below the 380,900 of 2000.
• Caution: the 2025 population is an estimate, not a census count; the jobs series covers the much larger metro area and starts only in 1990, so it cannot show the factory losses of earlier decades.

Mission 6: Hong Kong's own reservoirs supply only 20–30% of the water it uses. So how does it have water 24 hours a day?

Urban systems need infrastructure

• Infrastructure: the networks that keep a city working: transport, water supply, sanitation, waste disposal and telecommunications.
• As a city grows, demand outruns old systems, which are extended, replaced or rethought.
• Infrastructure follows growth, and also steers it: a new rail line opens up new districts.

Hong Kong's water problem

• Local reservoirs supply only 20–30% of consumption.
• Local yield can differ between years by up to 200 million m³.
• Hong Kong's "undulating terrain" makes rainwater hard to collect and store.

Response 1: water from the Dongjiang

• 15 November 1960: an agreement to import 22.7 million m³ a year from the Shenzhen Reservoir.
• 1965: imports of Dongjiang (East River) water began.
• Since 1982: 24-hour uninterrupted supply.
• 2003: a dedicated aqueduct separated the supply from all pollution sources along the Shima River.

Response 2: different water for different uses

• Of 1,292 million m³ used in 2018: local rainwater 21%, Dongjiang water 57%, and seawater for toilet flushing 22%.
• Since 2008, a Total Water Management Strategy has aimed to contain demand and develop new sources.
• Tseung Kwan O desalination plant has supplied drinking water since 22 December 2023, and is planned to meet about 5–10% of fresh water demand.

Sanitation: cleaning Victoria Harbour

• The Harbour Area Treatment Scheme (HATS): Stage 1, commissioned in December 2001, treated 75% of the sewage from both sides of the harbour.
• Stage 2A (works from July 2009; full operation on 19 December 2015) brought the remaining 25% to Stonecutters Island for treatment.
• HATS as a whole: more than 44 km of tunnels, up to 160 m below sea level, at a cost of HK$25.8 billion, serving more than 5 million people.

Transport: a rail-based city

• The Mass Transit Railway Corporation was set up in 1975.
• Today: 245.3 km of routes (metro, Airport Express and Light Rail), with about 5.64 million passenger journeys on weekdays.
• Since September 2018, a separate 26 km high-speed line has linked Hong Kong to the national high-speed network.

Older cities must renew: London's super sewer

• London's sewers carry rainwater and sewage together; in storms, combined sewer overflows spill into the Thames. In 2012 the EU Court of Justice ruled the UK in breach of EU law because of the volume and frequency of these spills.
• The 25 km Thames Tideway Tunnel "was fully connected and operational in February, 2025".
• Tideway reports that storm overflow volumes to the tidal Thames fell by about 86% in 2025 against the pre-Tideway average. The figure is based on modelled volumes, and 2025 was unusually dry.
• Cost: £4.7 billion, with average household bills rising by no more than £25 a year before inflation.

Evaluating infrastructure growth (AO3)

• Hong Kong first imported a resource, then diversified. Dependence on one river basin is a risk: the Dongjiang basin is already "an area of water scarcity".
• Big schemes take decades: HATS construction "spanned two decades".
• Costs fall on taxpayers or bill payers, and benefits may be measured by the operator itself (Tideway's 86% is modelled).
• Exam move: show growth over time: problem → response → new problem → next response.

Mission 7: In 2021 a coroner's report named air pollution exposure as a cause of a 9-year-old London girl's death. Who breathes a city's dirtiest air?

The urban heat island

• Urban heat island (UHI): built-up areas are warmer than the countryside around them.
• In the United States, urban areas are about 1–7 °F (about 0.6–3.9 °C) warmer by day and about 2–5 °F (about 1.1–2.8 °C) warmer by night than outlying areas.
• The difference is greatest in humid regions and in larger, denser cities.

Why cities are warmer

• Surfaces: roofs and roads absorb the sun's heat and release it slowly, so heat islands become "more pronounced after sunset".
• Less vegetation and water: less shade and less evaporative cooling.
• Urban geometry: tall buildings and narrow streets form urban canyons that trap heat and block cooling winds.
• Waste heat from vehicles, air conditioning, buildings and industry.

Impacts of urban heat

• Electricity demand for air conditioning rises 1–9% for each 2 °F (about 1.1 °C) of warming.
• Heat harms older adults, young children, low-income groups and outdoor workers most.

Managing urban heat

• Responses: trees and vegetation, green roofs, cool (reflective) roofs and cool pavements.
• On a warm day, conventional roofs can be up to 66 °F (about 37 °C) warmer than the air.

Air pollution: global patterns

• In 2019, 99% of the world's population lived where WHO air quality guideline levels were not met.
• Outdoor air pollution caused an estimated 4.2 million premature deaths in 2019; 89% were in low- and middle-income countries, most in WHO's South-East Asia and Western Pacific regions.
• Population-weighted exposure to fine particles (PM2.5) averaged 35.7 µg/m³ in 2015–2019 (UN SDG report on cities), against "the recommended air quality guideline of 5 μg/m3"; WHO is the custodian agency for this indicator.

Patterns within a city

• Place: roadside sites beside heavy traffic record more nitrogen dioxide (NO₂) than background sites away from main roads; London monitors both.
• Time: pollution peaks in rush hours; still, cold air (a temperature inversion) traps it near the ground.
• Sources: road transport is the largest single source of fine particles from within London, around 30% of emissions; over half of London's PM2.5 comes from outside the city.

London: a coroner's findings

• A coroner's report (Inner South London, 20 April 2021) concerned Ella Kissi-Debrah, who "died at the age of 9" after an asthma attack in February 2013.
• The recorded causes include "Air pollution exposure". She was exposed to NO₂ and particulate matter above WHO guidelines, and "The principal source of her exposure was traffic emissions".
• The report went to government departments, the Mayor of London and the London Borough of Lewisham, among others.

Who is most exposed?

• London, 2019: where the most deprived Londoners were likely to live, average NO₂ was 3.8 µg/m³ (13%) higher than in the least deprived areas, and PM2.5 was 0.7 µg/m³ (6%) higher.
• Compared with an earlier study (2013: 7.6 µg/m³), the NO₂ gap roughly halved; the authors say a precise comparison is not possible because the two studies differ.
• The authors warn that this "does not mean that any individual is necessarily exposed to higher or lower levels".

Who is most vulnerable?

• Over 600,000 Londoners live with a lung condition.
• WHO calls air pollution "one of the greatest environmental risks to child health".

Management: the Ultra Low Emission Zone

• The world's first 24-hour ULEZ began in central London on 8 April 2019, was expanded to inner London on 25 October 2021, and was extended across all London boroughs on 29 August 2023.
• Cars that do not meet the Euro 4 (petrol) or Euro 6 (diesel) standards pay £12.50 a day.
• The GLA estimates that in 2024 roadside NO₂ was 27% lower across London than it would have been without the ULEZ and its expansions: 54% lower in central, 29% in inner and 24% in outer London.
• Around 97% of vehicles seen driving in London were ULEZ compliant; a scrappage scheme had removed over 15,000 non-compliant vehicles by the time of the February 2023 report.

Evaluating the ULEZ (AO3)

• Strengths: large measured falls in NO₂ at roadside and background sites; the evaluation method was independently peer-reviewed.
• Method: the "without ULEZ" figures are estimates, made by comparing trends inside the zone with trends in outer London; the GLA says they show the impact of "all the Mayor's policies to reduce emissions from transport", not the ULEZ alone.
• Who pays: owners of older vehicles, including small firms and drivers who cannot easily switch; scrappage payments offset part of the cost.
• Unfinished: WHO's 2021 guidelines are stricter than UK legal limits; the coroner warned that national particulate limits are "far higher than the WHO guidelines".

Mission 8: In 2003 London began charging drivers to enter its centre. By 2007 traffic was still lower, but congestion was back where it started. How?

Measuring congestion

• Congestion: extra journey time caused by other traffic.
• Transport for London (TfL) measures excess delay: the travel rate in minutes per km above the free-flow rate, taken as the night-time rate.
• Congestion depends on traffic and on road capacity.

Patterns and trends in London

• Time: worst in the weekday peaks; TfL reports the morning peak.
• Space: TfL reports central, inner and outer London separately.
• Trend: "a sustained rise in congestion in all parts of London during the years leading up to the pandemic", then "slowly upward" since.

Impacts

• Average bus speeds were 9.3 mph in 2023/24, 1% lower than the year before; TfL says "increasing traffic congestion" held back the bus network's recovery.
• Congestion also means lost time, less reliable deliveries and more emissions per km in stop-start traffic.

The response: congestion charging

• February 2003: a £5 daily charge to drive in central London.
• July 2005: raised to £8. February 2007: the zone was extended westwards.
• Aims: reduce congestion, improve buses, make car journey times more reliable, and distribute goods more efficiently.
• Net revenues support the Mayor's Transport Strategy.

What happened to congestion?

• Excess delay in the original zone during charging hours, in minutes per km, against a "representative" 2002 value of 2.3:
  • 2003: 1.6 · 2004: 1.6 · 2005: 1.8 · 2006: 2.1 · 2007: 2.3.
• TfL's 2007 counts in the original zone still showed 21% fewer vehicles with four or more wheels than in 2002.

Why the benefit faded

• TfL attributes it to reduced road capacity: space given to "pedestrian, cyclist and bus priority measures and several major urban realm improvement schemes".
• Road works also rose sharply, mainly an "accelerated programme of infrastructure replacement by the utility companies"; TfL notes a range of other factors too.
• For the western extension, TfL concluded that "if the traffic removed by charging returned, congestion levels would be higher than those observed before the introduction of the extension".

Was it a success? (AO3)

• By traffic: yes, and lasting: 21% fewer four-wheeled vehicles in 2007 than in 2002.
• By congestion: lower for four years (2003–2006), with most of the gain gone by 2006 and all of it by 2007.
• By wider aims: space was given to buses, walking and cycling, which lower traffic made possible.
• Evidence: TfL measured against a "representative" 2002 value of 2.3, lower than the 2.5 actually observed, because 2002 had abnormal road works, some linked to installing the scheme itself; against 2.5, the 2003 fall would be 36% (computed).
• Since then: the Elizabeth line, opened in May 2022, adds rail capacity; it carried about 660,000 journeys a day by July 2024.

Mission 9: Two neighbourhoods on two continents: both were demolished and redeveloped. Who decides what replaces a neighbourhood?

Contested land use change

• Land use is contested when groups disagree about how it should change: residents, landowners, developers, local and national government, and NGOs.
• Three common types: slum clearance, urban redevelopment, and the depletion of green space.
• The driver is often rising land value (Mission 2), which puts low-income land uses under pressure.

Lagos: the context

• Lagos State's Ministry of Economic Planning and Budget estimated in 2013 that over 70% of Lagos's population lived in informal settlements (reported by Amnesty International).
• Amnesty reports that on 9 October 2016 the State Governor announced that all informal settlements along the waterways and creeks would be demolished within seven days; he claimed they were "used as criminal hideouts and posed a threat to the security of the state".
• Using community enumeration by the NGO Justice and Empowerment Initiatives, Amnesty says at least 40 such settlements are home to at least 300,000 people.

Neighbourhood 1: Otodo-Gbame, Lagos

• Amnesty International estimates that over 30,000 residents of the waterfront community of Otodo-Gbame were forcibly evicted in three operations: 9–11 November 2016, 17 and 21 March 2017, and 9 April 2017.
• The estimate deducts the people who remained (about 4,700) from an earlier population estimate; Amnesty says the government made no effort to count those affected.

Otodo-Gbame: the process

• All 75 Otodo-Gbame evictees Amnesty interviewed said they had received no prior written notice; Amnesty found no consultation, adequate notice or compensation, and no alternative housing.
• Amnesty reports the evictions went ahead in violation of court orders (7 November 2016; 26 January 2017) directing the state to refrain while the court decided.

Otodo-Gbame: reasons and outcome

• Amnesty reports that the government gave varying reasons, "from denying any responsibility to blaming the residents themselves, claiming to save the environment from degradation resulting from harmful inhabitation, to preventing crime".
• Amnesty (2017) reports that a luxury housing estate was being built on part of the cleared land and water area, with plots marketed at NGN45–200 million (US$124,710–554,269).

Neighbourhood 2: the Heygate estate, London

• A council estate in Southwark, completed in 1974 and originally housing about 3,000 people: 1,212 homes, 1,020 council-owned and 192 privately owned.
• A late-1990s survey found the buildings "structurally sound, but in need of complete refurbishment".
• In a 1998 consultation, 96% of responses favoured a major regeneration scheme.
• The redevelopment of the Heygate "has been the subject of a two-decade long controversy".

Heygate: its people and what replaced it

• In 2005 the 595 council tenants remaining on the estate were all given top (band 1) priority to move; 99% chose to stay in Southwark, and all were offered the right to return.
• Leaseholders received compensation under the statutory code; options included 20 shared-ownership homes in the Strata tower.
• Demolition was completed in July 2014; a planning application approved in January 2013 included 3,000 new homes.

Heygate: two views

• The council: "the combination of housing management challenges and regeneration opportunities" justified demolition.
• Some residents: "releasing the very significant value of the land was the key factor".
• A local campaign described the years of uncertainty as "a decade long act of attrition".
• Across London, 50 estates were regenerated in a decade: homes almost doubled, but there was a net loss of some 8,000 social rented homes.

A management response: resident ballots

• From 18 July 2018, landlords seeking GLA funding for estate regeneration that involves demolishing any social homes must win a resident ballot.
• The Mayor's 2018 guide says he will use his planning powers to require "no net loss of affordable homes", with like-for-like replacement, and "full rights to return or remain for social tenants".
• Evaluate: ballots give residents a real say, but only where GLA funding is used; they came after the Heygate decision.

Depletion of green space

• Built-up land is spreading faster than population: 43 m² per person in 1975, 63 m² in 2025.
• About 60% of the land converted to urban use since 1970 was productive farmland.
• Green space is contested because its benefits (cooling, flood storage, health, recreation) are shared, while development profits are private.
• One response: Barcelona's Superblocks aim at "reclaiming for citizens part of the space currently occupied by private vehicles", through "green hubs and squares where pedestrians have priority".

Comparing the two neighbourhoods (AO3)

• Similar: homes of lower-income residents cleared for redevelopment on valuable land. Amnesty reports luxury development on part of the Lagos land; at the Heygate, some residents say the land's value was the deciding factor.
• Different process: in London, a council decision with rehousing priority and a right to return; in Lagos, three eviction operations over five months, which Amnesty documents as without consultation, adequate notice or compensation, and in violation of court orders.
• Different scale: the Heygate originally housed about 3,000 people; Amnesty estimates over 30,000 were evicted from Otodo-Gbame.

Power and priorities (AO3)

• Who gains: landowners, developers and future residents; public budgets, through land value.
• Who loses: existing lower-income residents, especially renters and those without legal title.
• Protections that shift power: secure tenure, courts whose orders are respected, compensation, and rights such as London's ballots.

Mission 10: Singapore's prime minister guessed that protecting the island from rising seas would cost "$100 billion over 100 years". How can a city prepare for risks it cannot stop?

Resilient city design

• Resilience: a city's ability to withstand, adapt to and recover from shocks and long-term stresses.
• Climatic risks: sea-level rise, storm surges, intense rain and heat.
• Geopolitical risks: disruption to imported food, water or energy, from conflict or trade shocks.
• Strategies: protect (barriers), accommodate (build higher, store water), diversify (supplies) and retreat.

Example 1: Rotterdam, the trigger and the barrier

• On the night of 31 January to 1 February 1953 a North Sea flood drowned 1,836 people in the Netherlands; about five years later the government approved the Delta Act.
• The Maeslant Barrier, "a vital part of the Delta Works", was built 1991–1997 near Hoek van Holland. It has two gates, each 210 m wide and 22 m high, designed for a storm surge of 5 m above NAP (about mean North Sea level).

Rotterdam lives with water

• The barrier closes automatically when water near Rotterdam is forecast to rise more than 3 m above NAP; it first closed in 2007.
• Water squares store storm water in public space. Benthemplein, opened on 4 December 2013, has three basins: two fill whenever it rains, a deeper one only in prolonged rain.
• The idea became city policy in Rotterdam's second Waterplan (2007); Benthemplein was largely financed by water management departments and innovation subsidies.

Example 2: Singapore and the sea

• Mean sea level may rise by up to 1.15 m by 2100, and with storm surges and high tides, by up to 5 m. About 30% of the island is less than 5 m above mean sea level.
• As announced in 2019, new developments must be at least 4 m above mean sea level (formerly 3 m), and critical infrastructure such as Changi Airport Terminal 5 and Tuas Port at least 5 m.
• "Long Island", announced in 2023: about 800 ha of reclaimed land to protect the East Coast, including a new reservoir.

Singapore: food security

• Singapore imports more than 90% of its food, which leaves it vulnerable to "climate change, disease outbreaks, and geopolitical developments".
• Its response: diversify imports, build global partnerships, stockpile, and grow more locally, with targets for 2035.

Singapore: the Four National Taps

• Imported water from Johor, under a 1962 agreement that expires in 2061.
• Local catchment (rainwater).
• NEWater, reclaimed water, introduced in 2002.
• Desalinated seawater.

Evaluating resilient design (AO3)

• Cost: coastal protection at "$100 billion over 100 years" (Singapore dollars), paid now for risks that arrive later.
• Rare use: the Maeslant Barrier first closed in 2007, ten years after completion; its value lies in rare, extreme surges.
• Scale: Rotterdam pairs one national barrier with neighbourhood water squares part-funded by subsidies.
• Residual risk: Singapore's water agreement with Johor expires in 2061; diversification reduces dependence but does not end it.
• Exam move: judge resilience by cost, who pays and how much risk remains.

Mission 11: Urban areas use 75% of the world's energy. Vauban, a whole eco-district in Germany, is home to about 5,300 people. Can eco-cities and smart cities make a real difference?

Eco-city design and the ecological footprint

• Ecological footprint: the biologically productive area a population needs to produce what it consumes and to absorb its waste, especially carbon emissions, measured in global hectares.
• Urban areas consume 75% of global energy and produce 75% of greenhouse gas emissions (UN, citing the European Commission's Joint Research Centre).
• Eco-city strategies: energy-efficient buildings, renewable energy, less car use, recycling of waste and water, compact form.

Example 1: Vauban, Freiburg (Germany)

• A former French army barracks near the city centre; the site passed to the federal property office when the forces left in 1992.
• About 41 ha and about 5,300 residents (5,267, December 2020).
• "Not a car-free but a car-reduced district" (translated from German): residential streets have no public parking; car owners must buy a space in one of two district garages (about 470 spaces).
• A tram line has served the district since April 2006.

Vauban: how it cuts its footprint

• Low-energy construction is compulsory (65 kWh/m²); 277 homes were built to passive-house standard (at most 15 kWh/m² a year).
• In the Solar Settlement's plus-energy houses, more energy is produced than used.
• Heat (except for passive houses) comes from a woodchip-fired combined heat and power plant, whose electricity covers about 700 households.
• There are no rainwater sewers: rain runs in open channels to trenches where it soaks into the ground.

Example 2: Sino-Singapore Tianjin Eco-City (China)

• China and Singapore signed a framework agreement for the project in November 2007.
• Site: 34.2 km² of "non-arable land, deserted salt pans, and polluted water bodies" in the coastal Tianjin Binhai New Area, about 40 km from Tianjin's centre, so no farmland was taken.
• Planned for "350,000 residents and 190,000 jobs by 2020".
• Binding targets for 2020 included 100% green buildings, 90% of trips by walking, cycling or public transport (30% by 2013), 20% renewable energy and at least 50% of water from non-conventional sources.

Tianjin Eco-City: what was delivered

• The World Bank's completion report (January 2017) found "about 40,000 residents" by 2016.
• About 93% of buildings exceeded the green building standard; renewable energy in the public housing pilot reached 9.9% against a target of 60%.
• The eco-city calculated that 40–50% of trips in 2015 were "green trips".
• The report rated the outcome "Moderately Satisfactory" and linked slow population growth to the 2008 financial crisis, real-estate controls and delays to the light rail.

Evaluating eco-cities (AO3)

• Ambition against delivery: Tianjin had about 40,000 residents in 2016 against 350,000 planned for 2020.
• Evidence: Tianjin's results come from a World Bank completion report, though some figures (green trips) were calculated by the eco-city itself; Vauban's come from the city council.
• Scale: eco-districts house few people; most urban people live in existing cities, so retrofitting matters more.
• Site choice: building on salt pans and wasteland spared farmland, a gain the footprint does not show.
• Footprint: even a low-energy district imports food and goods; the footprint counts them.

Smart city design

• Smart city: uses digital technology (sensors, data platforms, automation) to run services such as traffic, lighting, energy and waste.
• Purpose-built: designed from scratch, with technology built in.
• Retrofitting: adding technology to an existing city.
• The UN lists "smart city" digital technologies among the ways cities can build resilience.

Purpose-built: Masdar City, Abu Dhabi

• A purpose-built district; construction began in 2008.
• It runs electric autonomous shuttles as a "living testbed" for new mobility.
• Its website says its buildings "use 40% less energy and water" than similar buildings; its own 2024 ESG report gives a 22.7% cut in energy use intensity and 13.1% savings in potable water, against benchmark baselines.
• Its 2024 emissions had "limited" independent assurance; it commits to net zero across all activities by 2050.

Retrofitting: Barcelona

• In November 2012 Barcelona City Council's Municipal Institute of Informatics began a project to define a smart-city strategy.
• Its Sentilo platform is open-source software for data from sensors deployed across the city.
• Superblocks retrofit the street grid itself. Their first phase (2020–2023) turned four Eixample streets, Consell de Cent, Rocafort, Borrell and Girona, into green axes with four new squares; the city gives each square as about 2,000 m².

Evaluating smart cities (AO3)

• Gains: real-time data for traffic, lighting and waste; open-source platforms avoid lock-in to one supplier.
• Risks: privacy and surveillance, cost, cyber-attack, and a digital divide among residents.
• Claims: compare headline claims with detailed reports, as Masdar's 40% against its own 22.7% and 13.1% shows.
• Reach: retrofitting reaches far more people than a new district, but must work around old infrastructure.

How Option G is examined (Paper 1)

• Paper 1 is 35% of the grade at both SL and HL. SL students answer on two options (1 hour 30 minutes, 40 marks); HL students on three (2 hours 15 minutes, 60 marks).
• For each option, allow 45 minutes: a structured question (10 marks) and one extended answer from a choice of two (10 marks).
• Any question may use a topographic map, and the guide names "Urban environments" as especially relevant.
• No Option G topic is on the guide's list of topics unlikely to suit the internal assessment fieldwork, so urban fieldwork is open to you.

What the top band rewards (question 2, 9–10 marks)

• "In-depth and question-specific (topic and command term)".
• Examples, statistics and details are integrated and explained, "explaining complexity, exceptions and comparisons".
• Evaluation weighs other perspectives and the strengths and weaknesses of evidence: estimated against measured results (ULEZ, Tideway), self-reported claims (Masdar), and what data cannot show (displacement).
• The conclusion is balanced and matches the evidence; maps and diagrams are annotated and support the argument.

The big ideas

• "Urban" is a definition: 58% or 81% depending on the rule. Hierarchies run from towns to 33 megacities.
• Bid rent shapes where activities and people locate; planning and policy modify it (Tokyo; Singapore).
• Poverty, informality and deprivation cluster, and persist across generations (Mumbai; England; Glasgow).
• Centripetal (migration, gentrification) and centrifugal (suburbanisation, counter-urbanisation) flows reshape cities; deindustrialisation empties them (Shenzhen; New York; Detroit).
• Infrastructure grows in stages: problem, response, new problem (Hong Kong; London).
• Heat, air pollution and congestion affect people unequally; judge management by its evidence (London).
• Land-use change is decided by power over land (Otodo-Gbame; Heygate). Resilient design layers protection and diversification (Rotterdam; Singapore); eco and smart design show what works, but retrofitting matters most (Vauban; Tianjin; Masdar; Barcelona).

Final screen. Score, the mission list ticked, and "Next: test yourself in the Verify stage" (links to the Verify quiz).