Research 350 - NZ Transport Agency

ECONOMIC DEVELOPMENT BENEFITS OF TRANSPORT INVESTMENT
• Whether SCBA is used alone or in combination with I-O analysis, regional economic
appraisals should also take into account impacts on other regions and the national
economy as a whole. Doing so would allow for an examination of inter-regional
displacement effects – or at least in comparison to the broader national viewpoint. Not
to do so risks presenting a distorted picture of net benefits (SCBA) or impacts (I-O
analysis).
5.3.4 Question 4.3
• Several methods may be used to measure the impacts of transport development on
specific socio-economic groups. These include financial appraisal, regression, survey
work, census data, origin-destination data, multi-criteria analysis (MCA) and
‘environmental justice’ approaches.
• However, some of these (e.g. MCA) are of questionable reliability.
• Cross-sectional information such as origin-destination (O-D) data, and, to some extent,
census data may help identify specific groups benefiting from changes in transport
infrastructure (e.g. unemployed, disabled, low income). Data which specifically and
directly relate the groups in question to transport improvements (such as O-D data
indicating travel time savings to low income earners) would be the most useful
approach in this respect. Merely inferring causal relationships between broad indicator
variables (such as arguing that a transport improvement has resulted in a nationwide
improvement in the incomes of low income groups) is of questionable utility in the
absence of firm theoretical/contextual backing.
• The use of O-D data may have several drawbacks, however, including difficulties in
attributing non-transport benefits, limitations on attributing net project benefits to
specific sub-groups and the usage of differential unit values in benefit calculations.
Further, cross-sectional approaches however, may be the lengthy timeframe involved in
project assessment. For example the transport behaviour of a ‘lower income’ subgroup
(and therefore the distribution of benefits) may change over time. This may
complicate estimation efforts.
• A partial solution to this issue may be the presentation of limited gross benefits based
on O-D data ‘below the line’ in an SCBA.
5.3.5 Question 4.4
• While the above methodologies may provide some useful data to policymakers, in
general, assessment of socio-economic impacts on specific groups should be seen as a
complement to the broader use of SCBA, in the first instance.
• As indicated, if policymakers are interested in determining the benefits (or otherwise)
accruing to specific groups then O-D data disaggregated into defined social groups
could be collected.
• It is noted however, that this process will involve additional costs. Further, the
difficulties and uncertainties associated with O-D data, noted above should not be
ignored.
110