Page 198 - Planning and Design of Airports

For ecasting for Airport Planning 165

and financing of the plan [3]. Though the basis for projections in a
system plan is the aggregate level of annual demand, this is not suf-
ficient for the master plan. Projections must be made for magnitude,
nature, and variation of demand on a monthly, daily, and hourly basis
on the many facilities located at the airport.
Annual forecasts of airport traffic during the planning period are
the basis for the preparation of the detailed forecasts in the master
plan. These forecasts are made for each type of major airport user
including air carrier, commuter, and general aviation aircraft and are
often expressed in terms of upper and lower bounds. The master plan
forecasts are usually made under both constrained and unconstrained
conditions. An unconstrained forecast is one which is made relative
to the potential aviation market in which the basic factors which tend
to create aviation demand are utilized without regard to any con-
straining factors that could affect aviation growth at the location. A
constrained forecast is one which is made in the context of alternative
factors which could limit growth at the specific airport. Constraining
factors addressed in master plans include limitations on airport
capacity due to land availability and noise restrictions, the develop-
ment of alternative reliever airports to attract general aviation
demand, policies which alter access to airports by general aviation
and commuter aircraft operations, and the availability and cost of
aviation fuel. The determination of the level of general aviation activ-
ity at an airport can be significantly changed when land availability is
restricted, thereby placing limits on airside capacity. The available
capacity may be utilized in the context of policies which favor com-
mercial over general aviation growth.
Specific forecasts made for a master plan include the annual,
daily, and peak hour operations by air carrier, commuter, general
aviation, cargo, and military aircraft, passenger enplanements, and
annual cargo tonnage, as well as daily and hourly ground access sys-
tem and parking demand. Projections are also made for the mix or
types of aircraft in each of the categories which will utilize the airport
during the planning period. In the preparation of these forecasts
some variables are projected directly and others are derived from
these projections. For example, annual passenger enplanements
might be forecasted from an econometric model and then, based
upon exogenous estimates of average air carrier fleet passenger
capacity and boarding seat load factors, annual air carrier operations
could be derived from these data. Guidance is provided by FAA
[3, 10] for forecasting the various elements of the master plan and
FAA recommends a tabular format for presenting forecasts for review.
An example is presented in Table 5-3. Although the activity elements
shown in the table refer to annual estimates, master plan forecasts
will also require peak period activity levels for the planning of many
airport facilities, and depending on the situation, seasonal, monthly,
daily, and/or time-of-day demands must be forecast.