The Algorithmic City
The city as represented by the transportation network.
- Shortest / fastest route
- High modeled access
The Core Idea
Two cities, one origin and destination
For the same origin and destination, the algorithmic “optimal” route and the perception-influenced route can be very different. That difference can change how accessible a place feels and which opportunities seem within reach.
The Perceived City
The city as experienced and interpreted by people.
- Perception-influenced route
- Perceived barrier
- Perceived positive
Why This Matters
Modeled accessibility is not experienced accessibility
Planning usually evaluates accessibility using the physical transportation network: where streets and transit services exist, how long trips take, and which destinations can theoretically be reached. But the network available on a map may not be the network people perceive as available to them. If perception systematically changes route choice, a gap opens between modeled accessibility and experienced accessibility. That gap can matter in at least four ways.
Accessibility
A destination may be physically close and technically reachable while perceived barriers make it effectively more distant. Two people living in the same place, facing the same transportation network, may therefore experience different sets of accessible opportunities.
Unequal Travel Burden
Perceived barriers may not be distributed equally. Differences in familiarity, past experience, perceived safety, physical ability, or knowledge of the network could produce different effective travel costs even when transportation supply is identical.
Effectiveness of Investment
Infrastructure can exist without being fully used. If people avoid a theoretically convenient street, station, crossing, or route because of how they perceive it, conventional measures may overestimate the benefit an investment produces. The question is not only whether infrastructure exists, but whether it becomes part of people's usable network.
Modeling
Most routing and accessibility models represent generalized travel cost through measurable attributes: time, distance, transfers, monetary cost. Actual route choice may include another component, perceived cost, that conventional models leave out.
Can spatial inequality exist not only in the infrastructure people have access to, but also in the network they perceive themselves as able or willing to use?
Where the Idea Comes From
Cities are navigated by mental maps, not only networks
Routing algorithms describe the city through objective, measurable information: time, distance, cost, and network connectivity. But in everyday life, people also make subjective judgments. Is this neighborhood safe? Is it pleasant? Is the detour worth it? Does this area feel connected to where I need to go?
When choosing between the same origin and destination, two people may take very different routes. The transportation network is the same, but their mental maps of the city differ. A neighborhood may feel unfamiliar, inconvenient, unsafe, or simply “not on the way,” even when an algorithm identifies it as part of an efficient route.
What happens when the city people perceive is different from the city represented by the transportation network?
A Conceptual Framework
-
01
Urban Environment
Built environment, land use, transit, and network structure.
-
02
Perception / Mental Map
How people perceive neighborhoods and routes.
-
03
Route Choice
Daily routing decisions shaped by perception.
-
04
Experienced Accessibility
Perception-driven access to jobs, services, and places.
-
05
Urban Outcomes
Impacts on mobility, equity, economic activity, and neighborhood vitality.
04 Experienced accessibility unfolds into
- Access to opportunities
- Effective travel burden
- Use of transportation infrastructure
- Spatial inequality
Physical connectivity does not necessarily imply experienced connectivity.
The project is interested in the gap between the transportation network that physically exists and the network that becomes behaviorally usable.
Project Questions
Three questions this project pursues
I want to understand how these differences in behavior affect transportation, neighborhood connections, and urban economic activity.
Quantify perception in routing behavior
Quantify how perception shapes routing behavior across different neighborhood and city contexts.
Measure experienced accessibility
Examine how perception-driven routing creates systematic differences between modeled and experienced accessibility.
Study the effects on cities
Study how these differences affect urban and economic outcomes.
Running through all three
- Where do perceived and physical networks diverge?
- How does this divergence affect route choice?
- Does it change experienced accessibility?
- Under what conditions does this mismatch become consequential for planning?
The last question is deliberately open. The project does not assume in advance that every gap between perception and the network requires intervention.
From Diagnosis to Intervention
Not every mismatch is a planning problem
Knowing that perception affects routing does not by itself tell planners what to do. A gap between the perceived and physical network can arise for very different reasons, and those mechanisms imply very different responses. So the first question is not how planners should change perception.
When does a mismatch between perception and the network become a planning problem, what produces it, and which intervention, if any, matches that mechanism?
-
Step 01
Identify the mismatch
The physical, modeled network on one side; the perceived, behaviorally used network on the other.
-
Step 02
Ask whether it produces a meaningful consequence
Reduced access to opportunities, additional travel burden, underuse of transportation infrastructure, or unequal experienced accessibility.
If not Intervention may not be warranted. Individual route preferences and differences in perception do not automatically constitute planning problems.
If so Ask what mechanism produces the gap, because each one points toward a different kind of response.
-
Step 03
Match the response to the mechanism
Four mechanisms can produce the same observed gap, and each implies a different intervention.
Physical or environmental barrier
Perception may reflect real characteristics of the environment: difficult crossings, poor pedestrian conditions, inadequate lighting, actual safety concerns, uncomfortable transit access, or physical discontinuities in the network.
Response Change the physical environment. The goal is not to persuade people that the barrier does not exist, but to address the condition producing the perceived cost.
Information or familiarity barrier
A route may be physically usable, but people may lack information about it or feel unfamiliar with it. Here the infrastructure itself may not need to change.
Response Wayfinding, better travel information, navigation support, and opportunities to build familiarity with alternative routes.
Persistent or outdated perception
The physical environment may have changed while people's mental maps have not yet updated. A previously unpleasant or difficult route may keep being avoided long after improvements are made.
Response Information about improvements, exposure to changed environments, and experience-based interventions that let people update their mental maps.
How quickly do mental maps respond when the physical city changes?
Routing or modeling mismatch
The problem may lie partly in how transportation models represent travel cost.
Generalized cost time + distance + monetary cost + transfers
Experienced generalized cost time + distance + monetary cost + transfers + perceived barriers
Response Incorporate perception into routing and accessibility models, which could eventually support routing systems that represent how travelers actually experience urban networks rather than assuming the objectively shortest route is behaviorally equivalent for everyone.
An Open Research Agenda
- 01Detect the gap
- 02Measure its consequences
- 03Identify its mechanism
- 04Match the intervention
- 05Evaluate whether perception and behavior change
Intervention depends on diagnosis. This framing lets the project move beyond documenting differences in route perception, while avoiding the assumption that perception is something planners should automatically try to correct.
When does physical connectivity fail to become experienced connectivity, why does that gap emerge, and what, if anything, should planners do about it?
By connecting human perception with route choice and accessibility, this project can help make transportation planning and urban policy more responsive to how people actually experience cities.