Urban planning decides how land and buildings are used, and it is the closest thing we have to designing an ecosystem on purpose. A sustainable city has to work on three fronts at once: it must be liveable for people now, affordable to run, and light enough on the environment to keep going. Miss any one of those and the plan fails.
📚 What you need to know
Urban planning is deciding how land and buildings in a city are used to meet residents’ needs.
A sustainable urban system balances the needs of the population with protection of the environment, now and for future generations.
Sustainability has three strands: social, economic and environmental. Good planning serves all three.
Key measures: affordable housing, integrated public transport, green space, safety, education and jobs, renewable energy, waste reduction, energy efficiency, water conservation and community involvement.
Transport is usually the highest-leverage decision, because it shapes the city’s layout for a century.
Every plan has trade-offs. Evaluation marks come from naming them.
Three strands, one city
Students often list planning measures without saying what kind of problem each one solves. Sorting them into the three strands fixes that immediately, and it is exactly what “to what extent is this sustainable” questions are asking for.
Use this to test any proposal in an exam: which strands does it serve, and which does it ignore? That question alone structures an evaluation answer.
What planners actually do
Measure
Strand
How it helps
Real example
Affordable housing
Social
Keeps workers near jobs and prevents forced sprawl to the edge
Social housing quotas in Vienna
Integrated public transport
All three
Cuts car use, emissions and congestion, and gives everyone access
Copenhagen’s cycle network; Curitiba’s bus rapid transit
Green space
Environmental and social
Cools the city, filters air, stores rainwater, supports health
Brasilia’s central linear park
Safety and security
Social
Good lighting and active streets make walking and cycling realistic
Street-lighting and public-space schemes in many cities
Education and employment
Social and economic
Keeps the population economically active and reduces inequality
University and skills districts worldwide
Renewable energy
Environmental
Cuts emissions from the city’s largest input
San Francisco’s electric vehicle charging network
Waste reduction and recycling
Environmental and economic
Turns outputs back into inputs and cuts landfill
Singapore’s waste-to-energy plants
Energy-efficient buildings
Environmental and economic
Insulation and solar cut both emissions and bills
Building codes across the EU
Water conservation
Environmental
Reduces abstraction from stressed rivers and aquifers
Dubai irrigating green space with greywater
Community involvement
Social
Plans that residents helped shape are used and maintained
Participatory budgeting in Porto Alegre
If you learn only three examples, make them Copenhagen for cycling, Curitiba for bus rapid transit and Singapore for waste. Between them they cover transport, emissions, cost and the circular use of resources, which is most of what this topic asks about.
Why transport is the biggest lever
Transport decisions do two jobs at once. They change emissions directly, and they change where people can live, which changes the city’s shape permanently. The emissions difference between modes is large enough to be worth remembering.
Note the caveat under each bar. Quoting a figure without the assumption behind it is exactly what examiners flag as uncritical use of data.
Copenhagen’s number to remember: more than 60% of residents commute by bicycle. That did not happen because Danes like cycling. It happened because the city spent forty years building protected lanes, secure parking and signal priority, while making driving in the centre slower and more expensive. Infrastructure changed the behaviour, not the other way round.
WORKED EXAMPLE
A city proposes building a new six-lane ring road to reduce congestion in its centre. Evaluate this proposal against the three strands of sustainability.
Step 1: the case for it
Through traffic is removed from the centre, which cuts local air pollution and journey times.
Economic: goods move faster, so business costs fall.Step 2: the environmental problem
The road takes farmland or habitat, adds impermeable surface, and makes land beyond the ring cheap to build on, so it encourages further sprawl.
Step 3: induced demand
Extra road capacity attracts extra journeys, so congestion typically returns within a few years and total emissions rise.
Step 4: the social problem
It helps car owners most. People without cars gain nothing, and communities can be cut in two by the road.
Short-term economic gain, long-term environmental and social costA stronger alternative would be investing the same money in public transport and cycling, which serves all three strands.
WORKED EXAMPLE
Classify each measure by strand and state one trade-off: (a) a new central park; (b) a congestion charge; (c) a large social housing scheme.
(a) Central parkEnvironmental and social. Cools the city, stores rainwater, improves health.
Trade-off: land in the centre is extremely valuable, and nearby house prices may rise and push existing residents out.
(b) Congestion chargeEnvironmental and economic. Cuts traffic and raises money for public transport.
Trade-off: it is regressive, hitting lower-income drivers hardest unless alternatives are already good.
(c) Social housingSocial, and economic if it is built centrally. Keeps workers near jobs.
Trade-off: expensive to build, and environmentally harmful if it is placed on the edge with no transport.
Every measure serves some strands and strains othersNaming a trade-off for each measure is the difference between a description and an evaluation.
💡 Exam tip
Sort every measure into social, economic or environmental. It gives your answer instant structure.
Name the city with the example. “Copenhagen, cycling” is worth more than a paragraph of general comment.
For “evaluate” and “to what extent” questions, give a benefit, a cost and a verdict.
Mention who benefits and who does not. Sustainability questions have a social justice component.
Use induced demand when discussing new roads. It is precise and few candidates know it.
Remember that planning decisions last for decades, so a bad layout is far harder to undo than a bad building.
⚠ Common mix-ups
Treating sustainability as purely environmental. The social and economic strands carry equal weight.
Assuming electric cars solve urban transport. They cut tailpipe emissions but not congestion, sprawl or road space.
Listing measures with no evaluation. A list scores low on any command word above “outline”.
Saying green space is only for recreation. It also cools, filters air and stores stormwater.
Confusing planning with building. Planning decides land use; construction follows.
Forgetting community involvement. Plans imposed without consultation are frequently unused or resisted.
Up next: Designing Cities as Ecosystems — the HL material on compactness, mixed land use and social mix, and why they work better together than separately.
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