INTERMODAL IMPACTS: INTERSTATE HIGHWAYS AND AIRPORT VIABILITY
The author examines the impact of individual interstate highway projects on airport viability in the State of Indiana from 1957 to 1970. The airports considered are or have been terminals for major trunk and local service air carriers since 1957. The total number of passengers carrier by air is taken as the measure of airport activity and viability. A multivariate time series methodology was used. It was found than the construction of new roads, which increases accessibility, is beneficial to larger airports but detrimental to the smaller local-service airports. /TRRL/
The Effect of the Interstate System on Short-Haul Air Passenger Demand
When an interstate highway is completed between two cities less than 200 miles apart, some people find it more convenient to switch from air travel between the two cities to automobile or bus travel. This paper employs a multiple regression model to quantitively examine this effect of interstate highway construction on short-haul air market. Several techniques are used to isolate the impact of changing highway quality on the short-haul air market from a myriad of other influencing factors. The city-pairs chosen for the regression sample are all between 105 and 185 miles apart so that the distance variable is constrained. An “airport use” variable is introduced to reflect changing environmental demand determinants such as income and population. The regression is run in first difference form, which eliminates multi-collinearities as well as the influence of static factors. Finally, quarterly data is used rather than yearly data to provide more degrees of freedom, and quarters are compared with the same quarters in an earlier year to eliminate the effect of seasonal variations. The coefficients of the resulting regression indicate two important conclusions. First, short-haul air markets are growing only about half as fast as the air market as a whole. Second, a significant number of travelers do switch from airplane travel to automobile travel when an interstate highway is made available for a one hundred to two hundred mile trip.
Airport Accessibility Affects Passenger Development
There is a meaningful body of knowledge currently (1964) available that indicates the need for taking the factor of airport accessibility into account when considering either locating a new airport or abandoning an existing one. The importance of this matter, the rationale for and against its acceptance, selections from factual data available and the engineers' responsibilities are among the primary areas examined. Failure to take the effect of accessibility, or inaccessibility, into account when locating an airport can lead to a chain reaction whereby passenger losses result in depressed airline revenue service, in depressed airport revenues and depressed ability to support airport development expenses. It is the professional responsibility of the engineers involved in airport work to be acquainted with these matters and to see that they are treated on a scientific basis. Failure to do this can lead to the development of airports that only partly serve the market, thereby betraying the initial economic justification for such airports.