IPCC Fourth Assessment Report: Climate Change 2007 Climate
Change 2007: Working Group III: Mitigation of Climate Change
Road transport: mode shifts  Personal motor vehicles consume
much more energy and emit far more GHGs per passenger-km than
other surface passenger modes. And the number of cars (and light
trucks) continues to increase virtually everywhere in the world.
Growth in GHG emissions can be reduced by restraining the growth
in personal vehicle ownership. Such a strategy can, however,
only be successful if high levels of mobility and accessibility
can be provided by alternative means.  In general, collective
modes of transport use less energy and generate less GHGs than
private cars. Walking and biking emit even less. There is
important worldwide mitigation potential if public and non-
motorised transport trip share loss is reversed. The challenge
is to improve public transport systems in order to preserve or
augment the market share of low-emitting modes. If public
transport gets more passengers, it