New publication: Accessibility with time and resource constraints

Mahmoudi, M., Song, Y., Miller, H.J. and Zhou, X.  (in press) “Accessibility with time and resource constraints: Computing hyper-prisms for sustainable transportation planning,” Computers, Environment and Urban Systems.


Accessibility is the ease of obtaining desired destinations, activities, or services in an environment. A common accessibility measure in basic and applied transportation science is the space-time prism (STP) and the network-time prisms (NTPs): these are the envelopes of all possible paths between two locations and times in planar space and transportation networks, respectively. STPs and NTPs focus on time as the scarce resource limiting accessibility. However, other resource constraints can constrain space-time accessibility, such as limits or “budgets” for energy, emissions, or monetary expenses. This paper extends NTPs to include other resource constraints in addition to time. Network-based resource hyper-prisms (RHPs) incorporate other resource constraints into NTP, capturing the trade-offs between time and other resources in determining space-time accessibility. We conceptualize RHPs as a constrained optimization problem and develop a forward and backward resource-dependent time-dependent dynamic programming to determine the boundaries of a RHP given time and other resource budgets. We illustrate our approach using the Chicago sketch network (with 933 nodes and 2967 links) for the use case of an individual with an internal combustion engine vehicle and a carbon emission budget and using portions of Washington, D.C. and Baltimore networks (with 12,145 nodes and 30,697 links) for the use case of siting electric vehicle charging stations to maximize regional accessibility.


Resource hyper-prisms; Space-time prisms; Accessibility; Sustainable transportation; Dynamic programming

Mesogeography Social physics, GIScience and the quest for geographic knowledge

New publication: Miller, H.J.Mesogeography: Social physics, GIScience and the quest for geographic knowledge,” Progress in Human Geography, 42, 600-609.

Abstract: The 20th century witnessed the rise of social physics: the application of models and techniques developed for physical processes to social phenomena. Social physics left an enduring legacy in human geography via its stepchildren, spatial analysis and GIS, shifting geography from microgeography (description-seeking) and towards macrogeography (law-seeking). Social physics is back in the 21st century, and its renaissance with a concurrent rise in computational and data-driven approaches to science and policy raises a wide range of concerns, including the claim that this is just macrogeography writ large: a single-minded pursuit of social laws at the cost of treating people as particles and spatial context as abstract and sterile. I argue that this time is different: a more sophisticated social physics, spatial analysis and GIScience are emerging that emphasize heterogeneity and spatial context as key drivers of interesting behavior. I also argue that new social physics suggests another path to geographic knowledge somewhere in the middle: mesogeography – a focus on how processes evolve in spatial context. I discuss GIScience techniques and approaches that can facilitate the quest for mesogeographic knowledge.

Keywords: GIScience, social physics, spatial analysis, spatial context, spatial heterogeneity

New paper – Street use and design: Daily rhythms on four streets that differ in rated walkability

Werner, C.M., Brown, B.B., Stump, T., Tribby, C.P., Jensen, W., Miller, H.J., Strebel, A. and Messina, A. (2018) “Street use and design: Daily rhythms on four streets that differ in rated walkability,” Journal of Urban Design, DOI: 10.1080/13574809.2018.1448706