Multi-Modal Public Transportation Accessibilityand the ARCADIA Project

Duncan Alexander SmithCASA Seminar, 17/11/10

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.

Interface for testing of policy Interface for testing of policy optionsoptions

Working with key London

stakeholders

Climate impacts assessment and Climate impacts assessment and adaptation planningadaptation planning

Analyse risks of• Flooding• Drought

• Urban heat and health impacts

Test adaptation options

Greenhouse gas emissions Greenhouse gas emissions assessment moduleassessment module

• Multi-sectoral emissions accounting

tool• Detailed sub-

modules for transport (personal and freight)Analyse of city-scale

energy policies

Land use and spatial Land use and spatial interaction moduleinteraction module

• Employment• Multi-modal transport• Developed land cover

• Population• Land use planning

constraints and attractors

MDM-E3 Multi-sector city-scale MDM-E3 Multi-sector city-scale economics economics modulemodule

• Dynamic resource interactions

between sectors• Specialist energy

sector module

Demographic scenariosDemographic scenarios City-scale climate scenariosCity-scale climate scenarios

• Temperature• Precipitation• Sea level rise• Storm surge

Urban Integrated Urban Integrated Assessment FacilityAssessment Facility

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 TransportationEnergy and carbon emissions from travel patterns.

Climate Event ImpactsEstimating accessibility impacts of transport infrastructure failures

from climate events (principally flooding).

Travel Cost MeasuresVarious 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 travelledEnergy use, Carbon emissions

Demand/Assignment costs-Service choices, flows, congestion.

Existing Accessibility and Transport ModelsGovernment/Consultancy Accessibility Models

TfL Capital Model, various Consultancy Models.

Journey Planning WebsitesMySociety 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 TransportOften 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)

Rail UG Bus Total

Trips Main Mode 2.2 2.1 3.5 7.8

Journey Stages 2.4 3.2 5.7 11.3

Public Transport Modes Included Journeys

1. Pedestrian

2. Underground

3. DLR, Overground

4. Mainline Rail

5. Bus

6. Bicycle

7. Car

Data Sources, Level of DetailStation LocationsEntry and exit interchange points. NAPTAN publicly available.

Infrastructure GeographyMeasure distances between stations. Ordnance Survey provide streets, mainline rail.

Timetable InformationAvailable from NPTDR. Highly detailed, all services and timetables. Simplified into AM peak frequency.

Street Network Representation

Use OS ITN street network (remove motorways)

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

Underground-DLR-Overground Network Representation

Service based representation to model interchanges and wait times.

Topological network, use timetable data.

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 Speed Group Speed Examples

High Speed 170 HS1 (St Pancras – Ashford)Moderate High 150 Great North EasternModerate 115-150 Great Western, Western Main LineLocal 90 Guildford, Maidstone, CroydonLow-congested 30-65 Thameslink

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

Time = 0Time = 12.5 Time = 25 Time = 37.5

Time = 17.5

Local Service, Speed 50 kmph

Express Service, Speed 100 kmph

Rail Network

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.

Bus Network Representation

Database Attribute Structure

Mode, Service ID, Link Time, Wait Time, Link Length

Service ID Link Traversal Time Interchange Wait Time1 Street Length / 5 kmph 0

2,LineID,BranchID Timetable 30 / Service Frequency

3,LineID,BranchID Timetable 30 / Service Frequency

4,TerminusID,ServID Link Length / Speed Class + stop delay 30 / Service Frequency

5,ServiceID Link Length / Speed Class + stop delay Stop density classification

6 Street Length / 12 kmph -

7 Street Length / ITIS speed -

Identifying Interchange Wait TimesRule for when service wait times are included:

Journey Time = Total Link Time + Total Interchange Delay

If fromEdge.ServiceID = toEdge.ServiceID ThenInterchange Delay = 0

Else Interchange Delay = toEdge.WaitTime

Service ID: 01 Link Time: 02 Wait Time 04

Service ID: 01 Link Time: 02 Wait Time 04

Service ID: 02 Link Time: 02 Wait Time 04

Time = 0Time = 2

Time = 4

Time = 8

Interfaces to the ModelMapping Interface Through ArcMapVisual, interactive, (slow!). Example

Toolbox / Scripting InterfaceFaster (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.

Travel Time Mapping- Bank

Travel Time Mapping- Kings Cross

Travel Time Mapping- Paddington

Travel Time Mapping- Croydon

Travel Time Mapping- Reading

Travel Time Mapping- Romford

Generalised Costs and DisaggregationBy applying an average cost per unit distance for each mode, calculate basic generalised cost. Also standard weightings for journey stages.

Standard Money-Time ConversionDfT WEBTAG guidance, £5.04 per hour.

Income and Demographic DisaggregationConversions between time and money highly dependent on income, need to perform demographic disaggregation first, yet to do.

1

2

30 mins£10

GC= £12.52

60 mins£3

GC=£8.04

Applying the Model to Commuting & Sustainability AnalysisCensus Commuting DataComprehensive sample flows, origins, destinations, main mode.

Assign to Network ServicesCalculate network distances, generalised costs and secondary modes, carbon emissions...

Absolute AssignmentMore realistic to assign probabilistically, logit model etc.

Applying the Model to Flooding ImpactsGeography of Service ClosuresCan 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 LimitationHow realistic to recalculate accessibility without capacity modelled?

The Challenge of Modelling PT CapacityCapacity Major ConstraintTube 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.

ConclusionsAchieved Multi-Modal PT Accessibility ModelCaptures 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 InfrastructureMapping highlights longstanding issue of orbital connections in Outer London, OMA. Car travel will be significantly faster.

Future TasksCommuting 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: duncan.a.smith@ucl.ac.uk

Urban Modelling Framework, Dynamics

Entrance and Exit TimesTime for Accessing Platforms

Creating Entrance and Exit Links to Stations