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. (2020) “GIScience, fast and slow – Why faster geographic information is not always smarter,” Progress in Human Geography, 44, 129-138.
Abstract. The growing maturity and deployment of low-cost georeferenced sensors, navigation systems, fast wireless communication, cyberinfrastructure and the Internet of Things (IoT) is accelerating the speed of geographic data flowing from the environment and our capabilities for reacting quickly to geographic information, often automatically and in real-time. This is leading to the rise of real-time GIS and smart cities technologies. While reacting quickly to changing circumstances has value, there are potentials for unintended consequences and rebound effects resulting from our inability to build geographic knowledge quickly and the selective acceleration of societal processes. This report discusses why these unintended outcomes may occur, and suggests technical and scientific approaches for understanding and managing the potential impacts of fast geographic data.
New publication: Park, Y., Mount, J., Liu, L., Xiao, N. and Miller, H.J. (2020) “Assessing public transit performance using real-time data: Spatio-temporal patterns of bus operation delays in Columbus, Ohio, USA,” International Journal of Geographical Information Science, 34, 367-392.
ABSTRACT: Public transit vehicles such as buses operate within shared transportation networks subject to dynamic conditions and disruptions such as traffic congestion. The operational delays caused by these conditions can propagate downstream through scheduled transit routes, affecting system performance beyond the initial delay. This paper develops an approach to measuring and assessing vehicle delay propagation in public transit systems. We fuse data on scheduled bus service with real-time vehicle location data to measure the originating, cascading and recovery locations of delay events across space with respect to time. We integrate the resulting patterns to construct stop-specific delay propagation networks. We also analyze the spatiotemporal patterns of propagating delays using parameters such as 1) transit line-based network distance, 2) total propagating delay size, and 3) distance decay. We apply our methodology using publicly available schedule and real-time location data from the Central Ohio Transit Authority (COTA) public bus system in Columbus, Ohio, USA. We find that delay initiation is spatially and temporally uneven, concentrating on specific stops in downtown and specific suburban locations. Core stops play a critical role in propagating delays to a wide range of connected stops, eventually having a disproportional impact on the on-time performance of the bus system.
KEYWORDS: Mobility, urban applications, public bus delay propagation, public transport reliability assessment, spatio-temporal data modelling