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12 I N N O VAT I O N S I N T R AV E L D E M A N D M O D E L I N G , V O L U M E 2
TABLE 1 Comparison of Design Features of Various Activity-Based Model Systems
Model Design Portland San Francisco New York Columbus
Feature METRO SFCTA NYMTC MORPC
Controls and no. of categories for 4 household sizes, 4 household sizes, 5 household sizes, 5 household sizes,
population synthesis 4 incomes, and 3 no. of workers, 4 no. of workers, 4 no. of workers,
4 ages 4 incomes, and and 4 incomes and 4 incomes
3 ages
"Usual" work and school locations at top level? Noyes Yes No No
Number of out-of-home activity purposes 3/8 3 4 7
Number of in-home activity purposes 3 1 1 1
Day pattern type linked explicitly across HH? No No No Yes, sequential
Joint activities linked explicitly across HH? No No No Yes
Allocated HH activities allocated explicitly? No No No Yes
"Escort" trips linked explicitly across HH? No No No No
Level where stop purpose and
frequency modeled Person-day Person-day Tour Tour
Network zones used (approx.) 1,250 1,900 6,000 2,000
Smaller spatial units used below zones? Noyes, 20K blocks No No No
Mode and destination model estimation Simultaneous Sequential Sequential Sequential
Network time periods per day 5 5 4 5
Modeled time periods 5 per day 5 per day 4 per day 1 hour
Use of time window duration in scheduling? No No No Yes
Tour time of day relative to mode Above both Above both Between them Between them
and destination
Departure time modeled separately at trip level? No No (may be added) No No
Accessibility measures in upper level models Person-specific Jobs reached by Destination choice Destination choice
modedestination zonemodetime logsums by zone logsums by zone
logsums band modesegment modesegment
a These model systems are currently in the design phase. HH = households.
behaviorally and because Census Transportation "USUAL" WORK AND SCHOOL LOCATIONS
Planning Package Table 1-75 provides a useful three- MODELED AT TOP LEVEL
way joint distribution of household size, number of
workers, and income for 2000. The Portland Metro The research community recognizes that the choices of
and San Francisco County Transportation Authority where to work and go to school are longer-term decisions
models have also used age of head of household as a that are not adjusted day to day, similar to the choice of
control variable, and the Atlanta Regional Commis- residence (which is implicitly modeled in the synthetic
sion, the Bay Area (California), and Denver are all sample). In most models, and all the more recent ones,
considering using age or age-related variables as well the "usual" work and school places are modeled at the
(e.g., presence of children, senior citizens, or both). top level, meaning that these are predicted before any
The sample-generation software created for Atlanta choices specific to the travel day are predicted. The home
has a flexible system for designating and combining location is typically one of the alternatives in the choice
control variables, as well as facilities for testing how set for people whose main workplace is at home or who
well the synthetic population matches other variables are homeschooled. Certain types of individuals, such as
for which there has not been explicit control. An construction workers or traveling salespeople, may not
important test will be how well the age distribution is have a usual workplace. And this model formulation
matched when age is not one of the explicit control requires that data be collected on each worker's most fre-
variables. quent work location, even if that person does not visit
