Activity Spaces and Travel Time in Sydney
D Olaru, University of Western Australia, AU; N Smith, T Ton, CSIRO, AU
The case study is Sydney, Australia, and the paper will report on the relationships between travel time expenditure and activity spaces for individuals and households using pooled data from the household travel survey (HTS) 1997-2002
Complex spatial and temporal ties mark each individual's mobility patterns, their accessibility needs and are reflected in their activity scheduling. While there can be large variation in people's tastes and preferences, there are also similarities in access needs and mobility options between population groupings. In particular lifecycle stages and gender affect both travel needs and options. This study investigates in a structural equation model the relationship between travel time expenditure and activity spaces across population groups at different stages of life cycle, with different ethnic background, and degrees of mobility restriction.
The activity space concept is based on a broad determination of space-time behaviour. In this research we include all locations visited by a traveller, reflecting his/her satisfied needs within the space-time and budget constraints. The activity space is an approximate measure of the size of the individual's mental map correlated with the costs of accessing different opportunities. In this respect, it reflects all three processes influencing accessibilities: scheduling of time-space budgets; the nature of the transport system, and the time-space organisation of accessed services - Church et al. 2001, Harvey and Taylor 2000. Both work and non-work activities are included in the measure.
The position of the centre of gravity of an activity space and the spread around it illustrate the degree of accessibility enjoyed by an individual, accounting for the importance of different locations in the household activities and available transport supply.
The case study is Sydney, Australia, and the paper will report on the relationships between travel time expenditure and activity spaces for individuals and households using pooled data from the household travel survey (HTS) 1997-2002.
For activity space we also compare the relatively simple derivation of an ellipse representing the part of the urban area visited by an individual or household on a certain day and the area of the polygon of visited locations (the coordinates of the activity locations weighted by the frequency of visits). The dispersion of the activities from the centre of gravity of all the activities, the urban area covered (the activity space), and time spent on travel were analysed across groups of individuals (defined by gender, age, life cycle, employment, car use) for weekday and weekend. Analysis was also conducted at household level.
The results have shown that life cycle stages have significant impact on the activity space and time spent on travel, mainly due to the different mobility needs of the households with different groupings, occupations and interests over a lifetime. Gender is also shaping differently the activity areas, and in general Sydney women have their activity space and travel time "budget" reduced.
Car availability and employment's positive impact on activity space and travel time expenditure found in this study is consistent with much research conducted previously. When comparison was made between weekday and weekend, the activity spaces increased for all categories during weekend, even if the travel time expenditure decreases. Gender and language group differences were not as prominent during weekend activities.
As expected, travel time expenditure is related to household characteristics and correlated with the activity space, which includes the most attractive destinations household members can achieve given the travel time. But the travel time expenditure was strong correlated with the polygon area and less with the activity space defined as an ellipse. This is because the activity space, defined by ellipse is higher than the area of the convex polygon connecting all visited locations.
Although not investigated at this stage, we hope to be able to also examine - by the middle of this year - the correlation between more traditional accessibility measures and the activity spaces.
Association for European Transport