Household location in response to changes in transport/accessibility – a microsimulation approach using SimDELTA

1. Household location in response to changes in transport/accessibility – a microsimulation approach using SimDELTA Olga Feldman, David Simmonds ESRC seminar May 2009

2. Presentation structure • DSC focus • DELTA • SimDELTA

3. Developers Residents Firms Transport infra- structure suppliers Transport service suppliers DSC focus Property market Labour market Product markets Transport market

4. Background to the DELTA package • Started in 1995 • Two key characteristics: • Add-on to otherwise free-standing transport models • The model be constructed in terms of processes of change. • Various applications in collaboration with transport specialists.

5. Structure of the DELTA model • The economic model • The urban land-use model • The migration model. • The transport model (to which DELTA is linked) • The meaning of “land use”: • Land-use modelling is usually concerned mainly with • households and population • employment • building stocks (housing, commercial) • the interactions between all of these and less concerned with land itself.

6. Structure of the DELTA model • The transport model (to which DELTA is linked) • The economic model • The urban land-use model • The migration model.

7. DELTA+a transport model sequence 2011 2010 2008 2007 2009 2006 Land-use database Land-use database Land-use database Land-use database Land-use database Land-use database DELTA DELTA DELTA DELTA DELTA Transport model Transport model

8. labour demand Economic model (investment, production and trade) Zonal model (household and job location, commuting) Migration model (longer distance household movements) labour population property housing costs consumption property costs migration transport costs freight demands transport costs travel demands Transport system immediate physical/demand quantities costs or generalised costs time-lagged Links between main submodels and transport model

9. Accessibility model – logsum approach Ai = accessibility of zone i Wj = opportunities at j (jobs by seg or retail floorspace) gij = generalised cost from i to j λD = distribution coefficient The logsum approach avoids arbitrary thresholds, and adding new opportunities or new modes always improves accessibility or leaves it unchanged

10. Accessibility use in DELTA

11. DELTA dynamics Simple sequence of processes within one year Complex time-lagged linkages over time Model is incremental in one year steps so starts from an observed database produces an updated database for each forecast year.

12. Zonal model Regional Model SPACE ACTIVITY Development (of floorspace) ACTIVITY ACTIVITY Transition (Households ) Migration Migration Car Ownership Regional Economic Model Location Residential Quality Employment (commuting) DELTA components within 1 year

13. Linkages within DELTA

14. SimDELTA

15. SimDELTA • A research project commissioned by DfT • The overall aim was to develop a new, microsimulation - based model of household location and related processes of change Main result • A new package named SimDELTA • has been developed and • Calibrated for the South and West Yorkshire – SWYSimM model; this area is chosen because of the existence of the modelling system for this area known as SWYSM (South and West Yorkshire Strategic Model) – DELTA + START

16. Microsimulation modelling area&2001 LA

17. SWYSimM modelling area

18. Data sources • 1991 and 2001 UK Census of population • 1991 Sample of Anonymised Records (SARs) • National Statistics • The British Household Panel Survey • Annual Survey of Hours and Earnings

19. SWYSimM • Full model – microsimulation and DELTA (linked to the transport model SWYSM but not the full land-use and transport model) • Microsimulation only – microsimulation only runs with some DELTA inputs • Static part 1 – to synthesise the initial database • Static part 2 – additional variables added • Dynamic part

20. Zonal model Regional Model SPACE ACTIVITY Development (of floorspace) ACTIVITY ACTIVITY Transition (Households ) Migration Migration Car Ownership Regional Economic Model Location Residential Quality Employment (commuting) DELTA components within 1 year

21. Zonal model Regional Model SPACE ACTIVITY ACTIVITY Development (of floorspace) ACTIVITY Transition (Households ) Migration Migration Car Ownership Regional Economic Model Household location Job location Residential Quality Employment (commuting) DELTA components New microsimulation components DELTA components within 1 year

22. SimDELTA diagram

23. Transport models • The transport model inputs are taken from the models developed for SWYMMS. • 2 transport models: • a Strategic model with about 90 zones, and involving aggregate representation of highway and public transport supply, linked to a DELTA land-use model to form a full land-use/transport interaction model; and • a ‘detailed’ model, employing 570 zones and involving explicit representation of individual highway links and public transport services. • The Detailed Transport Model (DTM) has been used as the main source of transport inputs for the household location research project (base year 2000).

24. Static model • JAVA coded simulated annealing model • 1991 Census and 1991 SAS data are used in the process • Output from simulated annealing contains all the Census variables from the SARS for each member of every household, not all needed • ‘Not defined’, ‘not adequately described’ variables had to be assigned values • Other variables had to be synthetically added, particularly • Household incomes, driving licences

25. Simulated annealing process (1) • A number of household records for one ward are taken at random from the microdata (SARs) • The characteristics of these households are tabulated and the resulting synthetic tables compared with real Census tables for this ward, and the error (mismatch) is calculated • Assuming there is a significant error between the synthetic and real tables, some of the selected households are swapped for an equivalent number of household records randomly chosen from the microdata, and the error recalculated

26. Simulated annealing process (2) • If the error has substantially increased, that swap is rejected, otherwise the swapped records are retained • Swapping continues until a best fit to the synthesized data to the real Census tables is reached • The analogy with the physical process of annealing centres on the “temperature” variable which is used to control the swapping of records: at high temperatures more records are swapped than at low temperatures.

27. Additional inputs • Socio-economic status • Economic status • Driving licences • Wage/Income • Assigning workplaces for workers in the base year • Potential cohabitees • Student households and shares

28. Static model Area data Dwelling data Household data Job data Person data Main outputs from the static model (1)

29. Main outputs from the static model (2) • Area data: area ID, population, households, families, jobs taken internally by seg, jobs available internally by seg, jobs taken externally by seg, accessibility, deprivation index, area centroid coordinates (easting, nothing), dummy: is external?, DELTA zone, DELTA area. • Dwelling data: dwelling ID, number of rooms, tenure, area code, dwelling type.

30. Main outputs from the static model (3) • Household data: household ID, dwelling ID, area ID, student house?, share house?, cars, income, tenure, families, preferred tenure, preferred number of rooms, mortgage value outstanding, mortgage years outstanding, savings, DELTA household type • Person data: person ID, household ID, family ID, area, age, sex, relation to head of household, marital status, seg, ethnicity, economic category, work area, driving licence, parent (for children), education level, job ID, preferred economic status.

31. Main outputs from the static model (4) • Job data: job ID, seg, economic status, economic status, area code, current wage, vacant?, person ID if occupied

32. Individual demographics Household changes Dynamic model Work related processes Household location Interface with DELTA Dynamic model processes

33. Individual demographics etc • Ageing • Survival • Moving to institution • Birth/multiple birth • Redundancy • Entering labour market/Staying in education • Leaving/re-entering labour market • Change job • Retiring from labour market • Becoming permanently sick • Becoming other inactive • Driving licence losing and acquiring

34. Household changes • Student households and other shares • Absence from households • Separation • Couple formation/marriage • Household Division • Household expenditure • Housing income • Obtaining/losing car

35. Work-related processes • Job supply • Identifying main earner(s) • Seeking to change job • Wages • Accepting/rejecting job/candidate • Job and workplace choices

36. Household location • Housing stock process • Housing prices or rents • Household in/out migration • Whether the household is seeking to move • Housing tenure choice • Dwelling choice • Location choice • Household location/relocation

37. SWYSM to microsimulation • Changes in labour demand (conversion of aggregate model results for employment into effects on job availability and redundancy) • Changes in housing supply (convert aggregate model results for housing development or demolition into addition/removal of dwelling objects) • Conversion of SWYSM forecasts of migration from the rest of the world into new household objects.

38. Other SWYSM outputs used as probabilities • Changes in car ownership • Migration between different parts of the microsimulated area • Migration from the microsimulated area to the rest of the world (i.e. leaving the model).

39. SWYSM DTM characteristics (1) • The base year is 2000 • Three time periods (morning peak, inter-peak, evening peak) • Validated road traffic assignment models for each time period, using SATURN software, with junctions explicitly modelled on the inter-urban network and link based speed/flow relationships used for major urban areas

40. Tests

41. Transport test M18 spur New junction

42. Artificial test Total population in the zones with improved accessibility Total population in all other zones

43. Conclusions • We believe that the present project has achieved a significant step forward in developing the first application of a working dynamic microsimulation of household change, location and commuting. • There are many modelling issues in need of further work. • Nevertheless we believe that the model as it stands can make a useful contribution to a range of other ongoing studies.

44. Acknowledgements • We are grateful to the former DfT Project Officers, Russell Harris and Mo Shahkarami, and to members of the project Steering Group for a number of helpful discussions during the course of the project, and for their patience during the delays which the project has incurred. Full report • is published the DfT website • http://www.dft.gov.uk/pgr/economics/rdg/hlm/