Environmental Engineering Reference
In-Depth Information
likely outputs from a series of interventions. Unsuitable impacts (and hence intervention
definition) can be revisited and remodelled. In this case, a distance-based charge for the
complete network, and better still an emissions-based charge, would lead to a greater reduction
in travel and emissions. The idea with the latter specification would be to charge vehicles by
distance travelled and type of vehicle, so that the heavier, more polluting vehicles pay more.
This orientates road pricing more to the goal of CO2 emission reductions. Hence the transport
planning process can be iterative, where interventions are redefined to optimise the achievement
against objectives. This is a critical element of objectives-based strategy development.
Low carbon transport and wider MCA impacts
The wider sustainability impacts of low carbon transport scenarios are also of great importance,
but seldom well understood. The spatial distribution of CO2 emissions across the county again
shows major CO2 reductions are made in the rural and car dependent areas in Oxfordshire,
relative to the BAU in 2030. Feasibly, some scenarios may be very beneficial in CO2 reduction
terms, but do less for social or economic objectives. INTRA-SIM allows us to 'read across'
the different metrics. Just four of the available indicators are discussed here - daily junction
delay (a proxy for the economy), accessibility by train (social), carbon monoxide (local
environment) and road fatalities (safety):
Daily junction delay: reduces in aggregate (by 32,000 aggregate seconds, or 20.8 per cent,
relative to BAU in 2030), hence traffic is viewed as travelling more 'smoothly' with less
delay at junctions.
Accessibility by rail to town centres: much increased accessibility in the areas surrounding
the mainline rail network (Reading-Oxford-Midlands) and assumed new networks
(Cotswold line upgrade; Evergreen 3, Oxford-Bicester-London Marylebone; and east-west
rail, Oxford-Milton Keynes-Cambridge-Felixstowe) with an increase in accessibility of
28.3 per cent relative to BAU in 2030.
Carbon monoxide: reductions are made virtually across the whole county with the
exceptions of clustered increases in some of the urban areas. There is a reduction of
5,399,618 kgCO, or 41.4 per cent, relative to BAU in 2030.
Safety: road fatalities reduce by 23, or 15.0 per cent, relative to BAU in 2030.
The economic metric can also be viewed as problematic. Junction delay (and annual car
time) is often used as a proxy to other economic indicators such as GDP growth. However,
this is a simplistic and often flawed view, indeed using such a measure by itself may mean
that measures to reduce CO2 emissions are not viewed 'positively' in economic terms. INTRA-
SIM has a wider variety of indicators available, but care is required in interpreting results,
particularly where available indicators need refining and where the impacts are often indirect.
Wider impacts can also be explored across the full MCA framework, but are not discussed
here. It is likely that appraisal methods need to change if major gains in CO2 reduction are
to be delivered through policy measures such as slower travel speeds; currently these are often
viewed negatively in time-savings calculations.
More radical interventions: towards a 60 per cent and deeper reduction
Scenario 3 delivers major gains in CO2 reduction and wider sustainability benefits. However,
it appears that reducing transport CO2 emissions on an area-wide basis by anything more
 
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