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Multi-Modal Public Transportation Accessibility and the ARCADIA Project. Duncan Alexander Smith CASA Seminar, 17/11/10. Multi-Modal Public Transportation Accessibility in GIS. Introduce ARCADIA - importance of accessibility in land use transport modelling.

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Presentation Transcript

Multi-Modal Public Transportation Accessibility

and the ARCADIA Project

Duncan Alexander Smith

CASA Seminar, 17/11/10

multi modal public transportation accessibility in gis
Multi-Modal Public Transportation Accessibility in GIS
  • Introduce ARCADIA- importance of accessibility in land use transport modelling.
  • Accessibility model- network representation and analysis
  • Results and applications – travel time mapping, commuting sustainability, flooding impacts.
  • Approach limitations- dealing with capacity, wider project challenges.
arcadia project
  • Aims-
  • “To provide system-scale understanding of the inter-relationships between climate impacts, the urban economy, land use, transport and the built environment.”
  • Collaborative project between several universities including Newcastle, Cambridge and UCL.

Demographic scenarios

  • City-scale climate scenarios
  • Temperature
  • Precipitation
  • Sea level rise
  • Storm surge

Urban Integrated Assessment Facility

MDM-E3 Multi-sector city-scale economics module

  • Dynamic resource interactions between sectors
  • Specialist energy sector module

Climate impacts assessment and adaptation planning

Greenhouse gas emissions assessment module

Land use and spatial interaction module

  • Analyse risks of
  • Flooding
  • Drought
  • Urban heat and health impacts
  • Test adaptation options
  • Multi-sectoral emissions accounting tool
  • Detailed sub-modules for transport (personal and freight)
  • Analyse of city-scale energy policies
  • Employment
  • Multi-modal transport
  • Developed land cover
  • Population
  • Land use planning constraints and attractors

Interface for testing of policy options

Working with key London stakeholders

importance of accessibility modelling
Importance of Accessibility Modelling
  • Key areas where accessibility/travel costs applied-
  • Modelling future geography of firms and residents
  • Input to land use -transport model, relevant to SCALE, GENESIS also.
  • Sustainability Impacts of Transportation
  • Energy and carbon emissions from travel patterns.
  • Climate Event Impacts
  • Estimating accessibility impacts of transport infrastructure failures from climate events (principally flooding).
travel cost measures
Travel Cost Measures
  • Various aspects. Joan discussing car travel, focus here on public transport.
  • Behavioural costs-
  • Travel Time- walk time, wait time, network service time, interchange.
  • Generalised Cost- include monetary costs, weight journey components.
  • Sustainability costs-
  • Mode choice, distance travelled
  • Energy use, Carbon emissions
  • Demand/Assignment costs-
  • Service choices, flows, congestion.
existing accessibility and transport models
Existing Accessibility and Transport Models
  • Government/Consultancy Accessibility Models
  • TfL Capital Model, various Consultancy Models.
  • Journey Planning Websites
  • MySociety Travel Time mapping work.
  • Need Flexibility & Control -
  • Travel cost measures
  • Network representation (future scenarios)
  • Zones , 2000*2000 matrix
  • Demographic, economic disaggregation
  • Study area of South East…
multi modal public transport
Multi-Modal Public Transport
  • Often in transport modelling ‘multi-modal’ translates as treating PT networks separately.
  • Multiple modes regularly combined in one trip in London context.
  • 2008 Weekday Millions of Public Transport Journeys (TfL)
  • (Analysis of LTDS, NTS needed for in-depth interchange patterns)
public transport modes included journeys
Public Transport Modes Included Journeys
  • Pedestrian
  • Underground
  • DLR, Overground
  • Mainline Rail
  • Bus
  • Bicycle
  • Car
data sources level of detail
Data Sources, Level of Detail
  • Station Locations
  • Entry and exit interchange points. NAPTAN publicly available.
  • Infrastructure Geography
  • Measure distances between stations. Ordnance Survey provide streets, mainline rail.
  • Timetable Information
  • Available from NPTDR. Highly detailed, all services and timetables. Simplified into AM peak frequency.
street network representation
Street Network Representation

Use OS ITN street network (remove motorways)

Standard walk speed: 5km/h (too slow for London?)

underground dlr overground network representation
Underground-DLR-Overground Network Representation

Service based representation to model interchanges and wait times.

Topological network, use timetable data.

mainline rail representation
Mainline Rail Representation
  • More complicated relationship with stops, e.g. express services.
  • Each service given separate link structure with frequency and speed classification tailored to service.
  • Over 150 rail services into London, rather than use timetable simplified into speed groups to measure travel time.
  • Speed Classes:

Rail Link Time = Link Distance / Service Speed + Station Delay (default 2.5 min)

Local Service, Speed 50 kmph

Time = 25

Time = 12.5

Time = 37.5

Time = 0

Time = 17.5

Express Service, Speed 100 kmph

bus network representation
Bus Network Representation
  • Should also be serviced based.
  • Hundreds of services with more variable route patterns. Requires fully automated method to generate network geometry from the timetable and stop databases.
  • Not complete. Currently using a simple proxy network using location and density of stops. No interchanges modelled, aggregate speeds for Inner London, Outer London, ROSE.
database attribute structure
Database Attribute Structure
  • Mode, Service ID, Link Time, Wait Time, Link Length
identifying interchange wait times
Identifying Interchange Wait Times
  • Rule for when service wait times are included:
    • Journey Time = Total Link Time + Total Interchange Delay
    • If fromEdge.ServiceID = toEdge.ServiceID Then
    • Interchange Delay = 0
    • Else
    • Interchange Delay = toEdge.WaitTime

Time = 4

Service ID: 01 Link Time: 02 Wait Time 04

Time = 2

Time = 0

Service ID: 01 Link Time: 02 Wait Time 04

Time = 8

Service ID: 02 Link Time: 02 Wait Time 04

interfaces to the model
Interfaces to the Model
  • Mapping Interface Through ArcMap
  • Visual, interactive, (slow!). Example
  • Toolbox / Scripting Interface
  • Faster (ish…), matrix calculations.
  • Interface Selections-
  • Choose which travel cost measure to minimise (travel time, generalised cost)
  • Choose which modes to be active (Select Query by ServiceID).
  • Choose origins and destinations.
generalised costs and disaggregation
Generalised Costs and Disaggregation


  • By applying an average cost per unit distance for each mode, calculate basic generalised cost. Also standard weightings for journey stages.
  • Standard Money-Time Conversion
  • DfT WEBTAG guidance, £5.04 per hour.
  • Income and Demographic Disaggregation
  • Conversions between time and money highly dependent on income, need to perform demographic disaggregation first, yet to do.

60 mins



30 mins


GC= £12.52


applying the model to commuting sustainability analysis
Applying the Model to Commuting & Sustainability Analysis
  • Census Commuting Data
  • Comprehensive sample flows, origins, destinations, main mode.
  • Assign to Network Services
  • Calculate network distances, generalised costs and secondary modes, carbon emissions...
  • Absolute Assignment
  • More realistic to assign probabilistically, logit model etc.
applying the model to flooding impacts
Applying the Model to Flooding Impacts
  • Geography of Service Closures
  • Can remove services from model, based on spatial extent of event. ‘Damage functions’ estimate severity, temporal dimension.
  • Underground highly exposed to flooding events, acts as drainage network.
  • Capacity Limitation
  • How realistic to recalculate accessibility without capacity modelled?
the challenge of modelling pt capacity
The Challenge of Modelling PT Capacity

Capacity Major Constraint

Tube strikes graphic illustration of capacity determining journey patterns in London. Road, bus travel at standstill, even pedestrian street network near capacity.

Could assign capacity to limits to service networks, validate against census commuting flows. Major task, have to be realistic about time-frame of project.

  • Achieved Multi-Modal PT Accessibility Model
  • Captures interchanges, more realistic journey routes and times. Service basis successful. Representational detail against performance trade-off, rather slow performance in ArcGIS, much faster without street network. Challenge of handling capacity issues.
  • Radial Nature of PT Infrastructure
  • Mapping highlights longstanding issue of orbital connections in Outer London, OMA. Car travel will be significantly faster.
  • Future Tasks
  • Commuting analysis based on accessibility model. Generalised costs. Comparison against car speeds, mode choice.
  • Useful for more automated methods for generating networks, particularly for bus.
  • Formal validation against other models, journey planners.

Thank you for listening! Welcome comments and questions.

Contact Email:

entrance and exit times
Entrance and Exit Times
  • Time for Accessing Platforms
  • Creating Entrance and Exit Links to Stations