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Chapter 3 | Scenario differences and model details
The proportion of national ADO consumption due to road transport climbed
steadily throughout the 1970s and 1980s, growing from about a quarter of total
sales in the mid-1970s to roughly half by the late 1980s, and remained reasonably
stable thereafter. This proportion has averaged close to 52 per cent over the last two
decades and appears to have reached a maximum value in 2002 (for both BITRE and
ABARE estimates) of about 54 (± 1) per cent.
However, recent ABARE sectoral statistics (see ‘Table F’ data on the ABARE web-site)
have the proportion of on-road diesel use falling quite sharply from 2003 onwards,
with results for the 2006 and 2007 financial years implying road sector contributions
(at about 46 per cent of total sales) lower than at any time since the early 1980s. The
current strong growth in the raw materials export market will tend to have contributed
to rising energy consumption by the mining and bulk rail sectors, and this could lead
to some decline in the road share of ADO use (and the BITRE trend estimates do
exhibit a slight drop in the road diesel proportion, from a value of 54.4 per cent in
2002 to a preliminary estimate for 2007 of 52.8 per cent). Yet BITRE is not aware of any
other aggregate trend indicators consistent with the magnitude of the sharp declines
in the road diesel share exhibited by the ABARE estimates for 2003 to 2006. 1
The result is a divergence between BITRE and ABARE estimates of road transport
ADO use for the last few years which, furthermore, appears to account for most of
the gap between BITRE and NGGI historical values for 2003 to 2005 national transport
emissions, and results in a difference of around 15 per cent for the currently
estimated 2006 road ADO values. If the weakening in road ADO growth within the
current ABARE figures happens to reflect actual activity, then the next update of the
BITRE demand models will have to be recalibrated to allow for the significantly lower
freight movement level implied. Alternatively, if further revisions to the ABARE time
series happen to move the estimated proportion (of road ADO use) back towards
the long-term historical average, then the NGGI values for aggregate transport CO 2
emissions over the last few years will need to be revised upwards (probably by about
2–3 per cent).
Business-as-usual assumptions
As specified previously, the current BITRE Base Case 2007 uses a ‘business-as-usual’
scenario that makes some adjustments for behavioural or technical trends possibly
affected by any of the various emission abatement measures already undertaken by
Australian governments by mid-2007.
To give an indication of how much this base case scenario specification might differ
from results using a purely BAU projection scenario (i.e. one that does not explicitly
include the effects of any government abatement measures), this section of the
report also presents some rough estimates of aggregate transport emissions using
a BAU trend that attempts to carry on from the average sectoral conditions that held
pre-2000.
1. Note that an inconsistency within the ABARE datasets could be involved in this estimation issue, where the original
values released for national use of ADO over the 2005 financial year were different in two of the main ABARE
historical data-tables. ABARE ‘Table F’ then quoted substantially higher ADO consumption for the 2003 to 2005
years than values given in their ‘Table K’ listing. The July 2007 update to these tables essentially fixed the divergence
for the 2005 financial year values, and more recent (2008) updates exhibit only a slight divergence for the 2007
financial year values—but, at the time of this report’s writing, there still remained around a 5 per cent gap between
Table F and Table K’s provided values for 2003, 2004 and 2006 (financial year) national ADO usage.
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