New publication: Jaegal, Y. and Miller, H.J. (2020) “Measuring the structural similarity of network time prisms using temporal signatures with graph indices,” Transactions in GIS, 24, 3-26.
Abstract. The network‐time prism (NTP) is an extension of the space‐time prism that provides a realistic model of the potential pattern of moving objects in transportation networks. Measuring the similarity among NTPs can be useful for clustering, aggregating, and querying potential mobility patterns. Despite its practical importance, however, there has been little attention given to similarity measures for NTPs. In this research, we develop and evaluate a methodology for measuring the structural similarity between NTPs using the temporal signature approach. The approach extracts the one‐dimensional temporal signature of a selected property of NTPs and applies existing path similarity measures to the signatures. Graph‐theoretic indices play an essential role in summarizing the structural properties of NTPs at each moment. Two extensive simulation experiments demonstrate the feasibility of the approach and compare the performance of graph indices for measuring NTP similarity. An empirical application using bike‐share system data shows that the method is useful for detecting different usage patterns of two heterogenous user groups.
New publication: Miller, H.J., Jaegal, Y. and Raubal, M. (2019) “Measuring the geometric and semantic similarity of space-time prisms using temporal signatures,” Annals of the American Association of Geographers, 109, 730-753.
Well-established techniques exist for measuring the similarity of space–time paths. These measures support clustering and aggregation of space–time paths as well as moving objects database queries based on similar movement patterns or semantics. Little attention has been paid, however, to the analogous problem of measuring space–time prism (STP) similarity, despite comparable applications. This article presents and evaluates a method for measuring STP similarity through dimensionality reduction that leverages their inherent temporal ordering. The technique sweeps an STP along the time axis and derives one-dimensional temporal signatures based on a measured STP property that captures its geometry or semantics. These temporal signatures can be visualized directly as curves. We can also apply existing space–time path similarity measures to these signatures. To demonstrate the feasibility of this approach, we perform two sets of experiments measuring geometric and semantic similarity among STPs and assess the information within these curves using visualization, Fréchet distances, and clustering techniques. Results suggest that the temporal signature curves capture meaningful similarities and differences among STPs.
Proffitt, D., Bartholomew, K., Ewing, R. and Miller, H.J. (2019) “Accessibility planning in American metropolitan areas: Are we there yet?” Urban Studies, 56, 167-192.
Abstract. Transportation-planning researchers have long argued that the end goal of a transportation system is increasing accessibility, or opportunities for individuals to meet their daily needs, but that US practice tends to focus on increasing mobility, or opportunities to travel farther and faster. This study finds evidence that the gap between theory and practice may be closing when it comes to accessibility, but that significant barriers still exist to the wider adoption of the accessibility paradigm among metropolitan planning organisations, the main entities responsible for regional transportation planning in the USA. We measure this gap by creating an accessibility index based on content analysis of a nationally representative sample of 42 US regional transportation plans (RTPs). We then use regression-tree analysis to determine the characteristics of metropolitan areas that are most likely to employ accessibility concepts. Finally, we identify barriers to a wider adoption of the accessibility paradigm. Most RTPs include accessibility-related goals, but few define the term or use accessibility-oriented performance measures. The lack of clarity on accessibility leaves vehicle speed as the fundamental criterion for success in most plans. Our analysis finds that MPOs serving large regions with high per capita income are the most likely to produce plans that focus on accessibility. We argue that such places produce more accessibility-oriented RTPs because they have greater planning capacity and recommend changes to federal planning guidelines that could speed the adoption of the accessibility paradigm in RTPs.