Human Energy Expenditures and Travel Time Budgets

Abstract

This research aims to explore the cause of stability in travel-time expenditures for an individual, which is seen to be invariant within the context of geographic location and time, and which is commonly known as the ‘travel-time budget’. The concept of biological energy expenditure on travelling is introduced in this research as a possible means to explain why travel-time expenditures have shown stability for a long time. The stochastic frontier modelling framework is used to estimate the ‘travel-energy budget’, which is seen as a controlling mechanism for travel-time expenditure. This research thus uncovers a very fundamental aspect from human physical considerations that has considerable implications in transport policy and practice. Even though understanding the similarity and variability of individual travel behaviour, particularly time use in travelling, has been considered one of the key issues in travel behaviour research for over four decades, limited availability of longitudinal data has restricted the analysis from deeper insights. Most of the past data in transport research come from self-reporting mechanisms. These self-report methods are fraught with error along with other problems. In contrast, GPS travel data has been regarded as more accurate, comprehensive, and complete in nature. This study aims to undertake a highly disaggregate analysis of travel-energy expenditures using multi-day and multi-year GPS data, which has never been studied in this way in the past. The greatest strength of this thesis clearly lies in its empirical contribution to address and explore new insights on travel behaviour and travel-time and travel-energy expenditures through the use of a novel multi-day, multi-period panel GPS data set. It contributes to the transport literature in theoretical and empirical aspects and the existence of stable travel-energy budgets. It also opens a new window of rethinking and making major changes in policy directions for transport.