Measuring transportation inequality using composite indices of accessibility
Creators: name: Sehatzadeh, Bahareh
Publisher: name: No Publisher Supplied
Year: 2017

description: It is argued here that transportation planners need to incorporate issues of equity into their agenda. Although recent efforts highlight the importance of establishing and utilizing new measures and standards to evaluate transportation performance on different criteria, equality and social considerations are still left out of the discussion to a great extent. Without such measures transportation agencies can hardly integrate the concepts of equality and social inclusion into their planning, programming, and project development activities.   Transportation inequality is a concept with many components and metrics developed to identify and measure it are varied. In the United States, concerns about providing equal access to social and economic opportunities has mostly centered on the issues of access to employment, healthcare, and food. In this study, however, I propose to look at transportation inequality through a social exclusion lens. Based on the academic literature on social exclusion, seven types of facilities and services are selected here as essential activities for social inclusion. These seven categories include education, employment, healthcare, social activities, retail, government and legal offices, banks and financial institutions.  To measure the accessibility of each of these categories three accessibility measures are used including travel time to the closest facility, average travel time to the three closest facilities, and number of facilities within 20 minutes of the origin. Furthermore, to understand the relative nature of access and social exclusion, distributional representations including the Gini coefficient, Sen welfare index, and access disadvantage index, are used here. Expert interviews and Analytic Hierarchy Process (AHP) are also used to determine weights of each category and calculate the overall composite indices. These measures are calculated using Los Angeles County and the City of Commerce as case studies. The analysis is extended to future scenarios where L.A. County’s transportation Measures R and M would be complete and the effect of these measures on access and inequality levels are evaluated.  Overall, what differentiates this study from the existing academic literature is that it combines several factors into its theoretical and methodological framework of measuring access inequality. The definition of accessibility here is multidimensional and covers access to multiple, essential services to support social inclusion. The study is also conducted at the household level and provides a more accurate representation of distribution of access. Basing the accessibility measurement on GIS network analysis as opposed to straight-line analysis help further this accuracy. Finally, using the Gini coefficient, access disadvantage, and the Sen welfare index helps form a new understanding of distribution of access levels throughout communities.  The analysis here is based on data mainly collected by the Southern California Association of Governments and the LA County Office of the Assessor. Similar data has been collected by other MPOs. Therefore the methodology here can be used to evaluate accessibility in other areas without the need for additional data collection and the results can be compared across regions.