Integrating people and place: A density-based measure for assessing accessibility to opportunities
28 Jul 2014-Journal of Transport and Land Use (Journal of Transport and Land Use)-Vol. 7, Iss: 2, pp 23-40
TL;DR: The goal here is to understand the magnitude and nature of the opportunities a mobile object had access to, given known location points and a time budget for its movement.
Abstract: Mobile object analysis is a well-studied area of transportation and geographic information science (GIScience). Mobile objects may include people, animals, or vehicles. Time geography remains a key theoretical framework for understanding mobile objects' movement possibilities. Recent efforts have sought to develop probabilistic methods of time geography by exploring questions of data uncertainty, spatial representation, and other limitations of classical approaches. Along these lines, work has blended time geography and kernel density estimation in order to delineate the probable locations of mobile objects in both continuous and discrete network space. This suite of techniques is known as time geographic density estimation (TGDE). The present paper explores a new direction for TGDE, namely the creation of a density-based accessibility measure for assessing mobile objects' potential for interacting with opportunity locations. As accessibility measures have also garnered widespread attention in the literature, the goal here is to understand the magnitude and nature of the opportunities a mobile object had access to, given known location points and a time budget for its movement. New accessibility measures are formulated and demonstrated with synthetic trip diary data. The implications of the new measures are discussed in the context of people-based vs. placed-based accessibility analyses.
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TL;DR: Results show that individual and place-based differences in food accessibility may be delineated with the metrics, and possible ‘deserts’ or areas of inaccessibility may be identified through a bottom-up analysis of the travel and mobility experience of a representative sample of individuals.
72 citations
TL;DR: In this paper, the authors investigated the accessibility of the older population to potential activities in a smaller metropolitan area in the state of Florida, using highly disaggregate spatial data containing the locations of populations and possible activities, and implemented accessibility models in a Geographic Information Systems (GIS) environment.
Abstract: Accessibility is facilitated by well-organized transportation systems that move people efficiently, and it is improved as more activities are reachable to people given the means of available travel. As the current population ages, it will ultimately challenge those who manage transportation systems in their attempts to satisfy the older population’s basic needs. Scanning the literature, accessibility has not been fully explored in relation to aging and older populations. We construct a systematic quantitative analysis of the older population’s accessibility to potential activities. Given their residential patterns and the prevailing transportation system, we ask whether they have as much potential accessibility to activities as their younger counterparts. Our study area is a smaller metropolitan area in the state of Florida. Using highly disaggregate spatial data containing the locations of populations and possible activities, we implement accessibility models in a Geographic Information Systems (GIS) environment, accounting for mode of transportation. Scenarios and activities analyzed are informed by a review of the broader literature as well as our own analysis of the 2009 National Household Travel Survey. We find that the potential accessibility of the aging population varies by activity type and differs with other age group cohorts. When we look in detail at subgroups within the aging population, the oldest group (those 85+) tends to have higher levels of accessibility.
61 citations
TL;DR: In this article, the authors highlight the impact of addressing competition for different urban services in the cumulative opportunities measure and show that considering competition changes the spatial patterns of accessibility and its equity.
51 citations
TL;DR: In this paper, the authors examined six income groups in the Los Angeles metropolitan area and found that job accessibility affects the employment status of medium-to-low income groups (household income between US$25,000 and US$75,000).
Abstract: Improving job accessibility can increase the probability for individual persons to be employed and reduce their commutes. Empirical research suggests that the relationship between job accessibility and employment outcomes differ across income groups, but no research has investigated the difference or explored which income groups benefit the most from job accessibility improvements. This research fills the gap by examining six income groups in the Los Angeles metropolitan area. Results show that job accessibility affects the employment status of medium-to-low income groups (household income between US$25,000 and US$75,000). For the lowest-income group (household income lower than US$25,000), owning a car significantly improves their chances to be employed, but job accessibility has no effect. On the other hand, higher job accessibility is associated with shorter commuting distance for the other five income groups, but not for the lowest-income group. These results suggest that transportation and land use policies need to address the specific needs of distinct population groups and underscore the importance of spatial access for the middle-class, which tends to be overlooked in the literature on transportation equity.
44 citations
TL;DR: The results of the case study show that the proposed location-based space-time accessibility measures can well capture the temporal variation of accessibility, due to the dynamics both of traffic conditions and of individuals' intensities in performing activities at different times of day.
41 citations
References
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TL;DR: This paper examines how different aspects of lifelines become relevant at refined or coarse granularities, which generalizes spatial and temporal aspects of movement allowing for an improved understanding of movement.
Abstract: This paper introduces a framework for modeling the movement of objects or individuals over multiple granularities. i>Granularity refers to selecting the appropriate level of detail for a task. At fine granularities, spatio-temporal information is revealed that was not previously known, such as additional locations that an individual visited or multiple visits to the same location. Conversely, moving to a coarser granularity or simpler view generalizes spatial and temporal aspects of movement allowing for an improved understanding of movement. Movement is modeled as i>geospatial lifelines, time-stamped records of the locations that an individual has occupied over a period of time. Depending on the desired granularity, lifelines are modeled as lifeline beads, necklaces, or more general approximations of these structures and this paper examines how different aspects of lifelines become relevant at refined or coarse granularities.
274 citations
TL;DR: In this article, the authors examined whether increased transit access is associated with the case status (employment status) of Temporary Assistance for Needy Families (TANF) recipients in the Atlanta, Georgia, Baltimore, Maryland; Dallas, Texas; Denver, Colorado; Milwaukee, Wisconsin; and Portland, Oregon metropolitan areas.
Abstract: Summary. While policy-makers assert that increased public transit mobility can positively affect employment status for low-income persons, there is little empirical evidence to support this theory. It is generally assumed that public transit can effectively link unemployed, car-less, persons with appropriate job locations—hence the call for more public transit services to assist moving welfare recipients to gainful employment. Thus far, the available evidence is anecdotal, while general patterns of transit access in relationship to labour participation remain relatively unexplored. This analysis examines whether increased transit access is associated with the case status (employment status) of Temporary Assistance for Needy Families (TANF) recipients in the Atlanta, Georgia; Baltimore, Maryland; Dallas, Texas; Denver, Colorado; Milwaukee, Wisconsin; and Portland, Oregon metropolitan areas. Individual TANF recipient location data, transit route/stop data and employment location data were used in limited dependent variable regression analyses to predict the employment status of TANF recipients. The results of this analysis indicate that access to fixed-route transit and employment concentrations had virtually no association with the employment outcomes of TANF recipients in the six selected metropolitan areas.
236 citations
TL;DR: An attempt to adjust the space–time prism concept of Hägerstrand's time geography to identify potential activity opportunities in virtual space, focusing on the virtual space access channels available in physical space.
Abstract: Today, the opportunity for potential human activity has gone beyond physical space to virtual space. Based on a proposed conceptual framework that models the relationships between physical and virtual spaces, this paper presents an attempt to adjust the space-time prism concept of Hagerstrand's time geography to identify potential activity opportunities in virtual space, focusing on the virtual space access channels available in physical space. A three-dimensional (3D) spatio-temporal Geographic Information System (GIS) design has been developed in this research to accommodate the adjusted space-time prism concept to support the representation, visualization, and analysis of potential human activities and interactions in physical and virtual spaces using the prism representation. Following the design, a prototype system has been successfully implemented in a 3D GIS environment. Such a system can provide powerful analytical tools for studies related to potential human activities and applications such as location-based services (LBS) and accessibility analysis in the information age.
194 citations
"Integrating people and place: A den..." refers background in this paper
...More robust visualization capabilities (Yu and Shaw 2008) coupled with the availability of high-resolution spatial movement data (Chen et al. 2011) has fueled these developments....
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...…study a wide range of topics related to transportation, such as analyzing human interactions in both physical (Yin, Shaw, and Yu 2011) and virtual (Yu and Shaw 2008) spaces, mapping people’s activity patterns (Kwan 1999), choosing destinations (Scott and He 2012), and modeling transport systems…...
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...As suggested above, many recent people-based accessibility approaches build on the timegeographic framework of Hägerstrand (1970) and incorporate such conditions within the enabling confines of GIS (Miller 1991; Kim and Kwan 2003; Neutens, Schwanen, and Witlox 2011; Yu and Shaw 2008)....
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TL;DR: This paper reports on the development of GIS software that implement space-time accessibility measures (STAMs), which reflect the benefits that individuals receive from the transportation system and are easily interpreted, particularly with respect to changes in accessibility.
Abstract: Transportation systems exist to improve individual accessibility. However, emerging applications of GIS in transportation (GIS-T) and intelligent transportation system (ITS) focus on throughput (the amount of system flow) rather than accessibility. Throughput is related but not equivalent to accessibility. Sensitive transportation planning requires rigorous, realistic and tractable accessibility measures. This paper reports on the development of GIS software that implement space-time accessibility measures (STAMs). The STAMs reflect the benefits that individuals receive from the transportation system. They are easily interpreted, particularly with respect to changes in accessibility. The STAMs also consider the locations and travel velocities dictated by the transportation system as well as individuals’ daily activity schedules. Tractable computational procedures allow calculation of the STAMs for detailed, urban-scale transportation networks. A prototype ArcInfo^®-linked software system that runs on Windows NT^® or Sun Solaris^® platform implements the STAMs with user-friendly interfaces and project management tools.
186 citations
TL;DR: A review of the contributions of the time-geographic approach to the closely related research areas of transport planning and accessibility analysis can be found in this paper, where the authors focus on the ways in which recent advances in time geography have deepened the understanding of human activities and travel possibilities.
179 citations