Environmental Engineering Reference
In-Depth Information
Strategic Policy
Aspiration
INTRA-SIM
MODEL
Multi-Criteria
Appraisal
Scenarios
With Different Levels
of Application
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Policy Packages
and Levels of
Application
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-
Policy Measures
and Long list of
Schemes
Figure 2.19
Scenario analysis and MCA
Source
: Saxena, 2012; Hickman et al., 2012b.
An important issue is that there is an increasing contribution of the transport sector to CO2
emissions, and little sign that transport is managing to reduce its emissions to any significant
degree. Measuring this, and discussing it, against MCA criteria, using a BAU scenario and
different future scenarios, can help make this more explicit to decision-makers and stakeholders.
For example, low CO2 strategies, whilst being effective in reducing CO2, may however have
adverse impacts against other policy goals. This is an important area that is poorly understood,
and there can be some progress made using MCA. Hence it is useful to move the debate
within scenario analysis beyond the generation of 'possible pathways' to consider what the
optimum pathways might be.
MCA is particularly useful where there is a wide range of potential impacts of projects or
initiatives. These can be examined, either in terms of efficacy, or for prioritisation, and typically
involve the assessment against a wide-ranging list of objectives or criteria. This can be a
combination of quantitative and qualitative assessment, and is seen as a major step forward
from using a cost-benefit analysis (CBA), where the impacts considered are often narrowly
defined. In practice the cost-benefit ratio is often used as one of the criteria within the MCA.
Transport investment planning is often described as a 'multi-criteria decision problem' because
projects typically have conflicting objectives. There is often no single optimal solution to
problems because objectives conflict and compensatory trade-offs cannot be established
(Guiliano, 1985). In the UK, the Department for Transport's (2012) web-based Transport
Analysis Guidance (WebTAG) represents the main MCA methodology used in transport
planning in the UK, and is increasingly used internationally as the basis of appraisals.
Although the use of MCA could offer an important step forward in assessing the benefits
of various scenarios, there are some inherent problems. A key difficulty, also found in the use
of CBA, occurs when impacts are difficult to quantify, or where there is disagreement in the
ascribed values. Many socio-economic impacts (land use, economic development, social
