result of environmental pressures. Certain Member
States of the EU reported rather large decreases in
emissions from road transport between 2007 and
2008, reflecting at least in part the lower amount of
freight transport by road in the second half of 2008
as a result of the economic recession [8]. In addition, the recession has had a significant effect on
car sales. Several governments have introduced
scrappage schemes to maintain or stimulate
demand for new cars, but these schemes should
also result in the replacement of older polluting
vehicles with new and more efficient ones. Data
sets from other regions also show the impact of the
economic climate. In 2008, in the United States,
the number of vehicles per 1,000 people decreased
for the first time since 1997. Similarly, total
vehicle-miles travelled decreased slightly from
2007 to 2008 – the first decline since 1980 [165].
Nevertheless, governments around the world
are acknowledging that action is required to control the rate of traffic growth, to improve the
environmental performance of vehicles, and to
increase public awareness about the impacts of
pollutant emissions from transport. As noted earlier, it is likely that the future shape of transport
will be influenced more by the need to reduce
greenhouse gas emissions than the need to
improve local and regional air quality. The development of a sustainable transport system will
involve a large number of interventions that are
beyond the scope of this entry, but will probably
include reducing dependence on cars, effective
land-use planning to reduce journey distances,
improving the quality of public transport,
etc. Preventative measures will also need to be
accompanied by mitigation measures which
reduce human exposure to air pollution.
For the control of local air pollution, it is likely
that emission legislation will still be the main
instrument for governments in the future. However, the future of European emission legislation
post-Euro 6/VI is somewhat uncertain. There is a
drive toward the global harmonization of legislation, but given that the threat of climate change is
increasing the pressure on manufacturers to
develop low-carbon power sources as alternatives
to fossil fuels (batteries, fuel cells, etc.), it is
therefore unlikely that the current test procedures
will remain relevant.
Shipping is currently one of the least regulated
emission sources, with a high reduction potential
through technological improvements, alternative
fuels, and ship modifications. It has been observed
that if the sulfur content of fuel oil remains at
present-day levels, a doubling in the emissions
of some pollutants from shipping can be expected
by 2050. However, given the increasing concern
about shipping-related air quality, further reductions of NO x and SO 2 emissions seem likely.
Using aggressive NO x emission reduction technologies, a decrease up to 85% in NO x emissions
could be reached through technological improvements by 2050, in spite of a growing fleet [166].
Research Needs
Emissions from transport, and the resulting ambient air pollution, have been studied intensively,
although there are still a number of areas where
the understanding is poor or incomplete. Some of
these areas are summarized below.
Testing Methods for New Technologies In legislative terms, the emphasis at present is on the
definition of appropriate procedures for the type
approval of hybrid-electric, full-electric vehicles
and hydrogen ICE vehicles. In some cases, certification will be problematic. For example, the current
heavy-duty engine test procedure cannot be applied
meaningfully to hybrid vehicles, as the instantaneous behavior of the engine is decoupled from the
instantaneous road load. Vehicle-based tests may
therefore become the norm in the future, although
this in itself introduces certain challenges given the
large number of possible vehicle configurations and
differences in real-world operation. Such challenges
might be overcome by the modelling of powertrains.
Understanding PM Emissions In recent years
evidence has accumulated indicating that airborne
particles exert a range of adverse health effects.
These effects are diverse in scope, severity, and
duration [4]. More work is needed in the future to
accurately characterize particle emissions from
surface transport modes and to uncover the mechanisms by which health impacts occur.
It has already been noted in this entry that a
better understanding of non-exhaust PM is
76
Air Quality, Surface Transportation Impacts on
States of the EU reported rather large decreases in
emissions from road transport between 2007 and
2008, reflecting at least in part the lower amount of
freight transport by road in the second half of 2008
as a result of the economic recession [8]. In addition, the recession has had a significant effect on
car sales. Several governments have introduced
scrappage schemes to maintain or stimulate
demand for new cars, but these schemes should
also result in the replacement of older polluting
vehicles with new and more efficient ones. Data
sets from other regions also show the impact of the
economic climate. In 2008, in the United States,
the number of vehicles per 1,000 people decreased
for the first time since 1997. Similarly, total
vehicle-miles travelled decreased slightly from
2007 to 2008 – the first decline since 1980 [165].
Nevertheless, governments around the world
are acknowledging that action is required to control the rate of traffic growth, to improve the
environmental performance of vehicles, and to
increase public awareness about the impacts of
pollutant emissions from transport. As noted earlier, it is likely that the future shape of transport
will be influenced more by the need to reduce
greenhouse gas emissions than the need to
improve local and regional air quality. The development of a sustainable transport system will
involve a large number of interventions that are
beyond the scope of this entry, but will probably
include reducing dependence on cars, effective
land-use planning to reduce journey distances,
improving the quality of public transport,
etc. Preventative measures will also need to be
accompanied by mitigation measures which
reduce human exposure to air pollution.
For the control of local air pollution, it is likely
that emission legislation will still be the main
instrument for governments in the future. However, the future of European emission legislation
post-Euro 6/VI is somewhat uncertain. There is a
drive toward the global harmonization of legislation, but given that the threat of climate change is
increasing the pressure on manufacturers to
develop low-carbon power sources as alternatives
to fossil fuels (batteries, fuel cells, etc.), it is
therefore unlikely that the current test procedures
will remain relevant.
Shipping is currently one of the least regulated
emission sources, with a high reduction potential
through technological improvements, alternative
fuels, and ship modifications. It has been observed
that if the sulfur content of fuel oil remains at
present-day levels, a doubling in the emissions
of some pollutants from shipping can be expected
by 2050. However, given the increasing concern
about shipping-related air quality, further reductions of NO x and SO 2 emissions seem likely.
Using aggressive NO x emission reduction technologies, a decrease up to 85% in NO x emissions
could be reached through technological improvements by 2050, in spite of a growing fleet [166].
Research Needs
Emissions from transport, and the resulting ambient air pollution, have been studied intensively,
although there are still a number of areas where
the understanding is poor or incomplete. Some of
these areas are summarized below.
Testing Methods for New Technologies In legislative terms, the emphasis at present is on the
definition of appropriate procedures for the type
approval of hybrid-electric, full-electric vehicles
and hydrogen ICE vehicles. In some cases, certification will be problematic. For example, the current
heavy-duty engine test procedure cannot be applied
meaningfully to hybrid vehicles, as the instantaneous behavior of the engine is decoupled from the
instantaneous road load. Vehicle-based tests may
therefore become the norm in the future, although
this in itself introduces certain challenges given the
large number of possible vehicle configurations and
differences in real-world operation. Such challenges
might be overcome by the modelling of powertrains.
Understanding PM Emissions In recent years
evidence has accumulated indicating that airborne
particles exert a range of adverse health effects.
These effects are diverse in scope, severity, and
duration [4]. More work is needed in the future to
accurately characterize particle emissions from
surface transport modes and to uncover the mechanisms by which health impacts occur.
It has already been noted in this entry that a
better understanding of non-exhaust PM is
76
Air Quality, Surface Transportation Impacts on