Irish passenger transport: Data refinements, international comparisons, and decomposition analysis

One of the most notable outcomes of Ireland's recent spectacular rise in income was an apparent 140% increase in domestic passenger transport fuel use from 1990 to 2008, at the same time as the car stock has more than doubled in magnitude. However, there have been very few comparisons and decomposition analyses of the data underlying this increase in travel. This paper addresses this gap by (i) refining passenger transport data estimates, in particular improving existing estimates of passenger-kilometre data, (ii) comparing trends in Irish private car ownership, usage, and activity to international historical trajectories, and (iii) performing a decomposition analysis of Irish passenger transport using the Refined Laspeyres Method. The international comparison indicates that Ireland's per capita private car usage and car activity have followed intermediate trajectories relative to the historical paths of Sweden and the UK. These trajectories of car usage and activity have contributed to the growth in fuel use, and the Refined Laspeyres decomposition formally decomposes the factors accounting for this growth. Activity was the main driver of the increase in fuel use, although intensity also contributed significantly. Despite decreasing load factors and average annual distances in cars, activity has continued to rise each year.

► Refinements are made to Irish passenger transport sector estimates on annual distance driven, load factor, and fuel use.
► Private car by relative share dominated passenger transport vehicle usage and activity.
► Irish private car usage and activity have trajectories intermediate to those of Sweden and the UK.
► A Refined Laspeyres Decomposition indicates activity accounted for 61% of the increases in fuel use.
► It is recommended that policy specific scenarios are developed on passenger transport fuel use.