Beyond the boundary: New insights from inside the space-time prism

Time geography is a perspective that focuses on the spatial and temporal constraints on an individual’s ability to participate in activities in a given environment (Hägerstrand 1970). A core concept is the space-time prism: this captures spatial and temporal constraints on potential mobility and activity participation. The prism demarcates all locations that a mobile object can occupy in space and time given: (1) the locations of origin and destination anchors; (2) the earliest departure time at the origin and the latest arrival time at the destination; (3) the maximum velocity for moving in space; and (4) the minimum required time for conducting stationary activities (Lenntorp 1977). Advances in geospatial science and technologies have greatly improved the realism of the space-time prism. GPS and other location-aware technologies (LATs) such as cellular phones and radiofrequency identification (RFID) chips enable researchers and practitioners to collect high-resolution mobility data. A number of database management systems (DBMS) such as Oracle, IBM DB2, PostGIS and ESRI Spatial Database Engine have extensions that support geospatial and temporal applications (e.g., Abraham and Roddick 1999; Egenhofer 1993; Lin 2012; Shaw and Wang 2000). These technologies facilitatethe wide application of the space-time prism in transportation science, urban planning, public health and other human sciences that are concerned with individuals’ mobility and accessibility (Bodzina and Cirucci 2009; Dong et al. 2006; Ettema and Timmermans 2007; Kwan 1998, 1999; Miller 1999; Neutens et al. 2007; Nicholls and Shafer 2001).