Improving Transport Project Appraisals
In the Islamic Countries
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the main railway network. The LMS and the NRM. Four NRM regional models are in use: NRM-
North, NRM-East, NRM-South, NRM-West. Long-term forecasts can be made with these models.
The Dutch Regional Model (NRM) is a traffic model that is used to calculate both the zero
alternative and the project alternatives in order to determine the accessibility effects of an
alternative. The NRM is used for infrastructure projects falling under MIRT program. The NRM
prepares forecasts for the road use of the project alternatives in order to determine the
accessibility effects. The NRM is a regional derivative of the National Model Traffic and
Transport System (LMS), which forecasts the mobility of persons in the Netherlands in 2030 and
2040.
The quality of the models is continuously kept in order by:
 Actualisations: the traffic models use input data that are subject to change. New decisions are
made about infrastructure and/or spatial development, new policy formulated or sometimes
renewed versions of the model software put into use. The starting points for the future are
therefore updated every year and new basic prognoses are drawn up on the basis of this.
These new basic prognoses are extensively tested for plausibility.
 The models are periodically subjected to an independent audit. The extent to which the
models are suitable for generating sufficiently detailed, reasonable and accurate answers to
a wide range of policy questions (fit for purpose) is examined. Also, to what extent themodels
fit in with contemporary (international) scientific insights and experiences with traffic and
transport models (state of the art) is examined.
2.1.6 Results of project appraisals
In all cases, a good CBA pays a lot of attention to uncertainties and risks. In this way, economic
research supports a policy decision that will inevitably be based on 'calculated risk'. The
outcomes of the CBA are not the only decision-criterion in the final decision-making about
transport projects and policies. In practice in recent years, projects with a low BCR are not
selected, whereas most but not all high BCR projects and policies get implemented. In order to
join the decision-making process, CBA can take place in two rounds. In the initial phase of
decision making, a large number of alternatives can be roughly analysed on the basis of 'key
figures'. After it has become clear on which search directions the research concentrates, a more
in-depth CBA can take place. Ultimately, politics decides on the basis of clear and relevant
information.
An important argument for not being able to attribute absolute value to the outcomes of an SCBA
study when making decisions is that applying the SCBA system in practice has major limitations
in addition to its advantages. First, an SCBA study is always incomplete. An SCBA study includes
many welfare effects, but is never able to include so-called unpredictable welfare effects.
Secondly, estimates of wealth effects in an SCBA study are always uncertain. Estimates are
uncertain because the SCBA tries to estimate effects in the future and the future is by definition
uncertain. Estimates are also uncertain, because in practice there is often insufficient time and
budget for the precise effects for a specific one project. Usually rules of thumb, key-figures and
other shortcuts are used in a SCBA. Another limitation of the SCBA is that effects that are difficult