Knowing that a city needs ten clinics is not the same as knowing where to put them.
Put them too close together and some neighbourhoods remain underserved. Spread them evenly and you may ignore population density, transport, capacity or need. Put everything in the geometric centre and you may optimise for nobody’s real journey.
Location–allocation is the geographic problem of deciding where facilities should be placed and how demand should be assigned to them.
Location asks where the facility goes. Allocation asks who it is meant to serve.
Quick Read: The Location–Allocation Mechanism
DEMAND POINTS + NETWORK + TRAVEL COST + CAPACITY + OBJECTIVE + CONSTRAINTS → FACILITY LOCATIONS + SERVICE AREAS
1. The Problem Starts With Demand
People, households, patients, students, customers or emergency incidents create spatial demand. The distribution of that demand matters because equal land area does not mean equal population or equal need.
2. The Network Matters More Than Straight-Line Distance
Facilities are reached through roads, railways, footpaths and transit. A clinic one kilometre away across a river may be less accessible than one three kilometres away on a direct route.
3. Different Objectives Produce Different Maps
One model may minimise total travel time. Another may minimise the worst journey. Another may maximise the population within fifteen minutes. Another may prioritise vulnerable groups. There is no single “optimal” location until the objective is stated.
4. Capacity Changes the Answer
A large hospital can serve more people than a small clinic. A school has finite places. A fire station has finite vehicles. Allocation must therefore respect capacity, not simply assign everyone to the nearest facility.
5. Fairness Can Conflict With Efficiency
A configuration that minimises total travel may leave one remote community with an extremely long journey. A fairer solution may increase average travel slightly to reduce the worst-case burden.
6. Location–Allocation Deepens Accessibility
Accessibility measures usable reach. Location–allocation asks how to redesign the facility geography so that reach improves.
7. It Also Addresses Spatial Mismatch
Spatial Mismatch identifies separation between people and opportunities. Location–allocation provides one family of tools for deciding whether moving the opportunity could reduce that mismatch.
8. Existing Facilities Create Constraints
Real planners rarely begin from a blank map. Existing hospitals, schools, roads, land ownership and budgets constrain what can move and what must remain.
9. Land Availability Matters
The mathematically best location may be impossible because the land is protected, too expensive, too small or unsuitable for construction. Geographic optimisation must operate inside real land constraints.
10. Time of Day Can Change the Optimal Site
Traffic and transit vary by hour. An emergency service located optimally at midnight may perform differently during the morning peak. Dynamic demand can require dynamic analysis.
11. Emergency Services Need Different Objectives
For ambulances and fire stations, the longest response time may matter more than average distance. Reliability and redundancy also matter because one blocked route can change the outcome.
12. Retail Uses the Same Logic Differently
A retailer may locate stores to maximise market capture rather than fairness. Competitor locations, customer spending and cannibalisation between branches become part of the geography.
13. Primary Geography: Where Should the Water Fountain Go?
Ask children where one water fountain should be placed in a playground. Should it be central, near the busiest area, near younger children or beside the sports court? The problem immediately reveals competing objectives.
14. Secondary Geography: Build Service Areas
Students can map homes and clinics, then compare nearest-distance assignment with travel-time assignment. The differences show why networks matter.
15. Advanced Geography: p-Median and Maximal Coverage
Location–allocation includes formal optimisation models. A p-median model seeks facility locations that minimise total weighted travel. Maximal coverage models seek to serve as much demand as possible within a chosen threshold. These are different questions and can produce different solutions.
16. Singapore Example: Everyday Services
In a dense city, locating schools, clinics, community facilities and emergency services involves population distribution, public transport, walking access, land scarcity and capacity. An apparently short island-wide distance can still conceal significant local variation.
17. Singapore Example: New Towns
As housing develops, service geography must follow changing demand. A facility map that worked for yesterday’s population may be poorly allocated for tomorrow’s.
18. Rural Example
Low population density creates difficult trade-offs. A small number of facilities may be efficient but impose long journeys; more facilities improve proximity but raise operating cost.
19. Hostile Test: “Just Put It in the Middle”
The geometric middle may not be the population centre, network centre or best site for vulnerable users. Optimality depends on the objective and the real transport network.
20. Where Location–Allocation Reasoning Breaks
- Centroid fallacy: assuming the geometric centre is best.
- Nearest-only thinking: ignoring capacity and service quality.
- Objective blindness: calling a solution optimal without stating what is optimised.
- Average-only fairness: minimising total travel while ignoring extreme burdens.
- Static-demand assumption: ignoring population and time-of-day change.
- Blank-map fantasy: ignoring existing infrastructure, land and budget constraints.
21. Ten Questions for Location–Allocation
- Where is demand?
- How much demand exists at each location?
- Which network connects users to facilities?
- What objective matters?
- What capacity does each facility have?
- What maximum journey is acceptable?
- Which groups need priority?
- Which sites are feasible?
- How does demand change over time?
- What happens if one facility fails?
22. Where This Fits
Accessibility owns usable reach. Spatial Mismatch owns geographic misalignment. This article owns the planning problem of choosing facility locations and assigning service areas.
The Idea to Keep
The best location is not a point on a map until we first decide what “best” is supposed to mean.