Environmental Engineering Reference
In-Depth Information
policy area. Each policy package can be selected at a variety of levels of intensity of 'application'
- typically at a 'low', 'medium' or 'high' level.
Relative to the rest of the UK and elsewhere internationally, London is unusual in that
traffic growth has been limited in recent years, and it appears to have reached the top of the
'S' curve of traffic growth. This may be related to various factors, including changes in
the macro economy, greater international travel and even a reduction in young people acquiring
a driving licence, but also the availability of high-quality public transport alternatives and
increasingly more comprehensive walking and cycling networks. Consequently, there are also
substantially lower levels of CO2 emissions in transport in London than for equivalent
populations elsewhere in the UK, as car ownership levels are lower and the use of public
transport is much higher.
Multiple scenarios can be developed within TC-SIM, allowing the comparison of potential
future policy trajectories, including possible 'trend-breaks' towards sustainable transport. All
can be examined relative to the BAU projection and each other. Each scenario includes a
variety of 'clustered' policy packages, representing a level of 'application' and a strategy for
implementation and investment.
For all policy packages and enabling mechanisms, the CO2 reductions are computed
relative to the BAU reference case. The BAU application is assumed to be the reference case
(Scenario 1) in T2025 (Transport for London, 2006). This broadly represents the current fully
funded investment strategy for TfL. It includes a significant amount of funding - approximately
£2-7 billion per annum to 2025 (Transport for London, 2006). If no policy package is selected
this is the equivalent of selecting the BAU option. Tailpipe emissions only are considered,
and travel only within the Greater London boundary. Obviously the definition of the reference
case is critical; a 'challenging' trajectory, with a large increase in emissions, means that the
impacts from policy interventions need to be significant if targets are to be reached.
Drivers of change
Following the conventional matrix approach to deriving scenarios, a number of drivers of
change, which at times compete in differing directions, are taken into account. These can be
existing trends or uncertainties which may impact on travel in London (
Table 3.4
).
Overview of scenarios
Multiple combinations of policy measures can be explored within TC-SIM, but the following
broad scenarios are examined within this chapter:
•
Baseline (1990-2006)
: historic trend in transport CO2 emissions.
•
Scenario 1 BAU Scenario 2030
: this future is an extension of existing trends over the
next 20 years - some investment in public transport, limited change in the efficiency of
the car stock and in the use of alternative fuels, but there is no coherent strategy for
accelerated change.
•
Scenario 2 - Lower carbon driving 2030
: achieves an approximate 25 per cent reduction
in transport CO2 emissions, on 1990 levels. However, this is reliant on an ambitious
implementation of technological measures (low emission motor vehicles and alternative
fuels) with a fleet wide average of 95 gCO2/km.
