Academic journal article Geographical Analysis

Space-Time Accessibility under Conditions of Uncertain Travel Times: Theory and Numerical Simulations

Academic journal article Geographical Analysis

Space-Time Accessibility under Conditions of Uncertain Travel Times: Theory and Numerical Simulations

Article excerpt

Recently, several accessibility measures using the space-time prism concept have been suggested in the literature. These measures fail to take into account (i) the ability of individuals to adjust their activity-travel patterns in coping with constrained choice sets, (ii) uncertainty in the perception of travel times, (iii) temporal variability of travel times, and (iv) the influence of travel information on accessibility. The aim of the present article is to contribute to this literature by addressing these four shortcomings. Theory will be developed and illustrated using numerical simulations. The results suggest that the accessibility measure proposed in this article is a useful indicator of social inclusion in terms of the time individuals can spend to conduct their preferred activities. Moreover, accessibility is found to be affected by the presence of schedule delay penalties, restrictions in time allocation to activities, and the provision of travel time information in order to reduce uncertainty.

Introduction

For more than four decades, accessibility measures have been developed to investigate the extent to which individuals can access jobs or services given their geographical location and available transportation options. The most commonly used accessibility measures include contour measures (e.g., Brabyn and Skelly 2002), potential measures (e.g., O'Kelly and Horner 2003), and utility-based measures (Small 1992). These accessibility measures have frequently been applied to assess the effect of developments in land use and transportation on individuals' opportunities to engage in particular activities. Examples include studies of the accessibility to jobs, to health care services, to population, and to stores. A topic that has reappeared on both the political and academic research agenda is social exclusion (e.g., Kenyon, Lyons, and Rafferty 2002; Lyons 2003; Miller in press). The concept of social exclusion refers to the situation that particular segments of the population may have relatively less access to particular service provisions in society. Although many factors, such as personal characteristics and cultural influences, may influence social exclusion, and social exclusion is a multifaceted and complex phenomenon, spatial factors may act as constraints, limiting people's access to service provisions and activity sites in general (Grieco 2003; Lyons 2003; SEU 2003). As argued by Schonfelder and Axhausen (2003) and Miller (in press), the concept of accessibility is therefore a relevant indicator of an individual's degree of social exclusion.

Irrespective of the domain of application, most traditional accessibility measures are limited in scope and are therefore insensitive to various policy concepts. First, a lack of accessibility may not only arise from a lack of transportation options as such but also from the need or desire to combine activities. For instance, Kwan (1999) illustrated that, given women's need to combine household and professional tasks, their labor market position and money-earning potential depend significantly on the opportunity to share household tasks with the spouse in a flexible way and on the spatial and temporal configuration of land uses. Similarly, Lyons (2003) suggested that, especially, the need to combine tasks combined with long travel times may prohibit individuals from participating in all activities that they find desirable.

Traditional accessibility measures (contour, potential, and utility-based measures) are not well suited for analyzing accessibility in the context of task combination as they assume that individuals make single-stop, single-purpose trips from home. In the context of time geography and activity-based analysis, there has been limited research on accessibility measures that combine multistop and multipurpose behavior (e.g., Arentze, Borgers, and Timmermans 1994a, b) with the space-time prism (Miller 1999; Kim and Kwan 2003). …

Search by... Author
Show... All Results Primary Sources Peer-reviewed

Oops!

An unknown error has occurred. Please click the button below to reload the page. If the problem persists, please try again in a little while.