Integrated Urban Models for Simulation of Transit and Land-Use Policies Final Report (1998) / Chapter Skim
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4.0 “Functional Design” of an Integrated Urban Model
4.0 “Functional Design” of an Integrated Urban Model
Pages 73-116
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From page 73... ...
2. Location choice: ibis includes the location choices of households (for residential dwellings)
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From page 74... ...
e - ~ ~ ~ - .~ I ~ ':::::':'2~'':1 ~ ~ ~:: -- 1 Activity / Travel and .- ~ -I ~ (-J`,ods Movement ~ ~:~ :~ I: it: :: Location Choice ~.
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From page 75... ...
That is, In the short run, most location choices are made within a "fixed" building stock supply. Similarly, in the short run, most activity/~avel decisions are made given a "fixed" distnbution of activity locations (and a fixed number of household autos)
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From page 76... ...
It also defines the goal towards which all such modeling systems should be striving, in that such a system would provide the analytical means for assessing the short and long run impacts of both transit and road alternatives in a balanced and comprehensive way. In particular, the long run impacts of major improvements in transit access on land development, residential and employment location choice - 52
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From page 77... ...
The impact of such pricing policies, however, feeds back through the system, potentially affecting modal choices (and perhaps other aspects of travel choice) , auto ownership, and possibly even residential and/or employment location choice.
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From page 78... ...
I Land-use Re/development, price, densification Residential and Job Locations HIGHWAY/TRANSIT NETWORK SOCIO DEMOGRAPHIC MICRO SIMULATOR* Individuals Households Fi~ms/Developers t 11 - 1 1 '1 DYNAMIC HOUSEHOLD VEHICLE TRANSACTIONS MODULE ~ ~ T ~ ACTIVITY-BASED DAILY TRAVEL SIMULATOR*
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From page 79... ...
.......... Linkage proposed Linkage suggested for later inclusion Area ~ HH no; r ~ Characteristics J Needs/ ~ HH~ Activin- Pattern \~ Rind Constrain: r M=datO~'~r Household Activity Simulator Routing Flexible ~l + - 1 Optlonal SpeedfConoestion ~ Net volumes by time of day ~ Net volumes by time of darer 1 ~ Net volumes by time of day 1 (E up by link)
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From page 80... ...
TCRP H-12 Final Report Figure 4.4 The Land-Use/Transportation Feedback Cycle Source: Wegener L1995] Mode choice He Route choice a/ / Firm loads / Travel times/ distance/costs 1 Accessibility Attractiveness Location decisions of investors Destination choice Transport Land Use ~~ Construction - 56 Tnp decision \ Car ownership Activities Location decisions of users
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From page 81... ...
Transit Improvements Transit Prionty Measures Transit User Subsidies J Employment Retail, etc. ==~_t Building Stock Residential Distributiont _ _ _ ~_ _ _ , .~'' ~ _ _ _ ~ 1 1 ., Non-Work Travel: _ _ · Generation ~ .
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From page 82... ...
4.3.2 Physical System Representation Fundamental to model design are decisions concerning the representation of the physical elements of ~e system: time, land (space) , buildings and transportation networks.
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From page 83... ...
TChP H-17 Final Report 1 1 Table 4.l Integrated Urban Mode} Design Issues Physical System Representation O Time O Space (land) O Building stock O Transportation networks O Services Representation of Decision Makers O Persons o Households ° Private firms O Public authorities Representation of Processes o Land development O Location choices o Job market O Demographics O Regional economics O Automobile holdings o Activity/trave} demand 0 Network performance "Generic Issues" O Level of aggregation/disaggregation 0 Endogenous versus exogenous treatment 0 Level of "process type" O Model specification Implementation Issues Dam requirements Computational requirements ,9
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From page 84... ...
Land development processes operate over time periods of decades or more; many househoid-leve! decisions are perhaps made on approximately a yearly basis (e.g., residential relocation decisions automobile transaction decisions, household structure evolution)
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From page 85... ...
Implicitly or explicitly, integrated urban models must address how they are going to represent the two primary active agents within cities: people arid firms. People generally live within either family or non-family units generally referred to as households.
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From page 86... ...
(given known employment locations) effectively combines residential land development, residential location choice and job 1ocahon choice into a single "net" or "reduced-form" model.
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From page 87... ...
. Residential location choice, employment location choice.
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. Given the complexity of most integrated urban models (typically involving many sub-models, each one of which possessing its own level of complexity, often exercised within a simulation framework)
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From page 89... ...
As with the model development data requirements, the forecast input data requirements must also be considered during the model design process, and, again, may well impose significant practical constraints on model design with respect to the temporal, spatial and/or behavioral representations which are feasible to achieve. Integrated urban models are well known to be extremely " data-hungry".
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From page 90... ...
my' S , . ' - 66 Specification Error Model Complexity Spatial/Temporal Precision
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From page 91... ...
Historically, the computing power cost-e~ectively available to researchers arid Earners has imposed significant limitations on the scale and scope of integrated urban models. Past arid continuing avarices in computer technology, however' are fast removing these barriers.
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From page 92... ...
Validation o Representation of/sensitivi~ to transit Feasibility O Computational requirements O Data requirements O Technical support requirements O Cost leasability O Ease of input preparation O Mode} run the ° Output/presentation capabilities O Portability/transferability O FIexiblity/adaptability 4.4.2 Credibility' Criteria This set of criteria deal with the basic confidence one has in a given model. as well as the suitability of the mode]
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From page 93... ...
Mile this criterion is effectively already covered by the "policy sensitivity-" criterion discussed above, it has been listed separately here in order to reflect the motivating objective ofthisproject: to assess the extent to which integrated urban models adequately capture the transit - land-use interaction. This includes "both directions" of the interaction: the extent to which transit services and facilities effect urban land-use, arid the extent to which urban form affects transit usage.
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From page 94... ...
Integrated urban models can easily possess the same or even greater problems in this regard. Model run time.
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From page 95... ...
Section 4.5.3 then works through this model design in detail, using the set of design issues introduced Table 4.2. Finally, Section 4.5.4 provides a brief summary of the key elements in the model design.
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From page 96... ...
This paradigm has evolved and been institutionalized over more than a forty-year period. It represents the embodiment of the collective experience of a large number of individuals and agencies worId-wide who have engaged In operational travel demand modeling over this very long time period.
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From page 97... ...
The focus of that discussion was on motivating the importance of each issue within the model design process. rather than on deciding how to best address each issue within a particular mode} implementation.
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From page 98... ...
and lon~,-run (land development, transportation infrastructure, etc.) processes.
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From page 99... ...
Considerable inertia exists with respect to many decision processes, especially major ones such as land-use and location choice. This is likely due to a number of factors including: imperfect information (an actor may not know that there is a better alternative available)
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From page 100... ...
For example, it may well be perfectly reasonable to argue that the modeiina of mowing peak-period flows on the road network for a "typical" day within a one-year time step can be handled within an equilibnum framework (given current land-use, etc.~. This is because the adjustment process associated with these daily peak-penod flows is very fast relative to the land-use and location choice processes which are the determinants of the activity patterns generating the ori~in-dest~nation flow patterns being assigned.
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From page 101... ...
and are fast approaching a practical, operational capability. Given the long time-frame for lar~-use and location choice processes, integrated urban models should be feasibly applied to forecast time periods of at least 20 years, and perhaps up to as much as :0 years, into the future (recognizing the Increasing uncertainty associated with moving further and further into the future)
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From page 102... ...
model to the Tonger-term components is lagged from one or more previous time periods. For example, travel utilities from the previous the period may be used to define accessibilities which enter into location choice decisions in the current time period.
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From page 103... ...
without an explicit representation of building stock, it is impossible to constrain properly location choice decisions. Built space can be measured either In terms of the number of 'units' (typically the most useful measure when dealing with residential housing)
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From page 104... ...
; and other attributes as required and available. Transportation Networks.
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From page 105... ...
how such detailed operational models impact arid He impacted by integrated models. are questions for fimber research and testing.
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From page 106... ...
In addition however, public authorities are typically major employers arid consumers (and providers) of land, floor space, transportation and other goods and services within urban areas and so have endo~enous roles to play within the mode]
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From page 107... ...
· Household role · Employment (related attributes;: - potential occupations - current employment status: - not in labor force - unemployed - employed: -part time/fulltime - occupation - job location - u age (and taxes) · Education related attributes - highest level of schooling attained - current educational status: - not a student - part time / fills time - level - location - 8:
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From page 108... ...
y - If yes: - mode - fleet size Public Authorities fit e., · Industry type according to unique · Finances functional location) - revenues - costs · Inputs - capital - number jobs by occupation type - other goods and services Commodities etc.)
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location choice processes, travel, and automobile ownership. As has already been discussed, individual actors (persons, firms, etc.)
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.. -:~: -- Market :::- ~ :::: -- I :- -:~::Demanders : :~ : -:: Suppliers Housing Market Household Public authorities Developers Household Floor Space Market ~Firms Developers Public authorities Firms Goods and Services ~ Persons Firms Market (includes Households Public authorities education)
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In order to accomplish these tasks, public authorities (just like private firms) enter markets to demand labor, space, goods and services, and transportation.
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From page 113... ...
These attributes are grouped according to the three main categories defined in Table 4.1: physical system, decision makers and processes. Land development, location choice processes, and job-worker linkages are all modeled as economic markets with explicit supply and demand functions and procedures for price determination and "market clearing" (i.e., the allocation of supply to demand)
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From page 114... ...
Public Authorities: Represented within the mode! to the extent they generate purely endogenous effects (employers of workers, demander / supplier of services; etc.~.
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From page 115... ...
are representative at each point of time being modeled and are sufficiently detailed to support the behavioral decision models being used. Regional Economics: Essential components of urban production / consumption processes should be modeled endogenously.
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From page 116... ...
TCRP H-12 Final Report - 92
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