SACOG Conformity Determination

is based on a survey, rather than comprehensive information collected and checked continuously. It
remains possible but unlikely that the models show today’s travel accurately, but for the wrong
reasons.
SACOG’s model must overcome more uncertainties in forecasting future conditions, as would
be the case for any kind of prediction about the future. The model is sophisticated enough to
take into account, on a region-wide average, travel changes as a household evolves from a young
family with working parents and children to a family with teenage drivers and eventually to a
family of retirees, and other young families come along behind. In fact, the models can take into
account many kinds of changes, but must specifically be told to do so. For example, travel cost
may change due to higher gasoline prices, parking fees, or transit fares. New technologies could
affect performance of the system; for example, connected traffic signal systems or autos with radar
that can travel safely closer together. The reasons and ways people travel might change; for
example, due to Internet shopping, telecommuting, or broader use of small, slow motorized
vehicles like golf carts or scooters. Clearly, things could evolve in different ways by 2025.
Changes such as these require SACOG to envision future conditions based on the way things
look now, and tell its models what to assume. A model’s calculations will be no better than
the vision and instructions it is given.
Future land use patterns generated the most contention. SACOG estimated future land uses
based on policies of current local General Plans, but development could unfold differently.
SACOG tried to develop a more sophisticated transportation model that not only would adjust
travel patterns away from highly congested areas, but was unable to get it ready to use in time for
this plan. Alternatively, SACOG could have developed one or more arbitrary different future land
use patterns and loaded them into its models, but chose not to do so because the work would have
been labor-intensive and costly with no up-front consensus as to what alternative patterns to use.
Historically, General Plans have not reflected future development patterns very accurately,
so the model’s forecasts do carry some risk of inaccuracy here, but still remain the best
information available.
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