This paper deals with assessing some social and environmental effects of transforming a
large airport into a real multimodal transport node. Such transformation implies connecting
this given airport to the High-Speed Rail (HSR) transport network, which enables the
substitution of certain Air Passenger Transport (APT) mainly short-haul flights with equivalent
HSR services. This substitution can occur through competition and/or because of
complementarity of the two modes. The effects include potential savings in the quantities
and related costs of social and environmental impacts such as airport airside delays, noise,
and local and global emissions of greenhouse gases. A methodology for quantifying these
savings is developed and applied to a large European airport according to the ‘‘what-if’’ scenario
approach.