Page 184 - Planning and Design of Airports

For ecasting for Airport Planning 151

movements can be made. From these estimates concepts for the lay-
out and sizing of terminal buildings, runways, taxiways, apron areas,
and ground access facilities may be examined.
Forecasting demand in an industry as dynamic as aviation is an
extremely difficult matter, and if it could be avoided it undoubtedly
would. Nonetheless estimates of traffic must be made as a prelude
to the planning and design of facilities. It is very important to remem-
ber that forecasting is not a precise science and that considerable sub-
jective judgment must be applied to any analysis no matter how
sophisticated the mathematical techniques involved. By anticipating
and planning for variations in predicted demand, the airport designer
can correct projected service deficiencies before serious deficiencies
in the system occur.

Levels of Forecasting
Demand estimates are prepared for a variety of reasons. Broad
large-scale aggregated forecasts are made by aircraft and equipment
manufacturers, aviation trade organizations, governmental agencies,
and others to determine estimates of the market requirements for
aviation equipment, trends in travel, personnel needs, air traffic con-
trol requirements, and other factors. Similarly, forecasts are made on
a smaller scale to examine these needs in particular regions of an area
and at specific airports.
In economics, forecasting is done on two levels, aggregate forecast-
ing and disaggregate forecasting, and the same holds true in aviation.
From the inception of the planning process for an airport consider-
ation is given at both levels. In airport planning, the designer must
view the entire airport system as well as the airport under immediate
consideration. Aggregate forecasts are forecasts of the total aviation
activity in a large region such as a country, state, or metropolitan area.
Typical aggregate forecasts are made for such variables as the total
revenue passenger-miles, total enplaned passengers, and the number
of aircraft operations, aircraft in the fleet, and licensed pilots in the
country. Disaggregate forecasts deal with the activity at individual
airports or on individual routes. Disaggregate forecasts for airport
planning determine such variables as the number of originations, pas-
senger origin-destination traffic, the number of enplaned passengers,
and the number of aircraft operations by air carrier and general avia-
tion aircraft at an airport. Separate forecasts are usually made, depend-
ing on the need in a particular study, for cargo movements, commuter
service, and ground access traffic. These forecasts are normally pre-
pared to indicate annual levels of activity and are then disaggregated
for airport planning purposes to provide forecasts of the peaking
characteristics of traffic during the busy hours of the day, days of the
week, and months of the year. As appropriate to the requirements of
an airport planning study, forecasts of such quantities as the number