Impacts on greenhouse gas emissions as
well as mitigation and adaptation measures to reduce those emissions
can vary widely depending on how passengers, freight, and
information are transported. Further, transportation is expressed
in terms of modes of travel, which are categorized broadly as
occurring by land, air, and water. Within that broad categorization,
transportation modes may also be classified in terms of the
physical infrastructure that is used and include those that use
rail, road, ships, and airplanes, each of which can be subdivided
further. Land-based transportation systems are generally those
with the highest usage in urban regions, and can be divided
into rail- and road-based systems. According to Kahn-Ribeiro
et al. ( 2007 , p. 328), “road vehicles account for more than
three-quarters” of total transport energy use and thus associated
greenhouse gas emissions. This combination of what (or who)
is being transported and the mode by which it is transported is
signifi cant because it provides a measure of the amount of greenhouse
gas emissions by modes and types of uses. This measure
of emissions in turn helps in devising adaptation and mitigation
strategies. Finally, the nature of regulation and other forms of
oversight and management of the transport sector have a critical
effect on emissions.