As time progresses, New Zealand’s population is projected to increase, with a changed age structure. In particular, older age groups are projected to increase much more than younger age groups, which, in some cases, are projected to fall as a percentage of the overall population. As personal travel tends to decrease for those aged 55 years and older, this change in the population’s age structure is likely to result in reduced travel compared to the travel of a population of the same size and with the present age structure. It is also likely to result in a road user population with different characteristics and needs from the present population.
This research, undertaken in 2010, has projected both future household travel on the road network and safety levels, based on measures derived from New Zealand Household Travel Survey data and official road safety statistics. The projections have been made using three population projection series from Statistics New Zealand:
- series 1 representing low population growth
- series 5 representing medium growth
- series 9 representing high growth.
The ‘mortality’ variable underpinning these series has been used as a rough surrogate for health status. Such questions as ‘to what extent will women increase their travel in the future relative to men?’ and ‘to what extent will older persons’ per capita travel increase or decrease with changed health status or economic growth?’ are addressed qualitatively, rather than in the projections. This is because no population projections are available to shed light on these issues. Time budgets for travel are also treated qualitatively.
The projections prepared as part of this report for household travel on New Zealand roads between 2006 and 2056 suggest that estimates which ignore the changing age structure of a population may overstate the change in travel by around 40%.This is related to large projected increases in the 65+group (273% by 2061), who have a lower propensity to travel relative to younger groups.
Looking at the three New Zealand population projections, differing mainly in regard to mortality assumptions, changes in population health factors make a relatively small difference up to around 2020, but greater variation appears after that time.
Authors: William Frith, Opus Central Laboratories, Lower Hutt, New Zealand; M. Kelly Mara, MKM, Wellington, New Zealand; Jim Langford, Monash University Accident Research Centre, Monash University, Melbourne, Victoria, Australia.