Glossary

Term	Meaning
Accessibility	The ease with which relevant destinations can be reached from a location. See Accessibility.
Attraction ($A_j$)	The size or quality of a destination: jobs, floor space, capacity, places.
Attraction potential	The contribution of one destination to one origin's accessibility, being attraction times travel potential.
Betweenness	Share of shortest paths in a network that pass through a node. See Network centrality.
Catchment area	The set of locations served by a facility. See Isochrones and catchment areas.
Connector, OD connection road	The link joining an origin or destination point to the network. Result of a connect operator.
Contour measure	Synonym for a cumulative opportunity indicator. See Accessibility indicators.
Cut off	A maximum impedance beyond which routing stops and destinations are ignored.
Decay function	A decreasing function converting impedance into travel potential. See Distance decay functions.
Detour factor	Ratio of network distance to straight line distance. See Euclidean versus network distance.
Generalised cost	Impedance combining time, money and penalties in a single unit. See Travel impedance.
Impedance	The cost of traversing a link or a route: time, distance, money, or a combination.
Isochrone	The area reachable within a given travel time.
Junction free section	A chain of links containing no junctions, replaceable by a single link. See Network optimisation algorithm.
Link	An edge of the network graph, connecting two nodes. Referred to by its from node F1 and to node F2.
Logsum	Expected maximum utility over a choice set, the basis of utility based accessibility measures.
MAUP	Modifiable areal unit problem, results depending on zoning scale and boundaries. See Zoning and spatial units.
Node	A vertex of the network graph.
OD matrix, trip table	Impedances between all origins and all destinations. See Origin Destination matrix (trip table).
Potential accessibility	Sum over destinations of attraction times travel potential.
Space time prism	The set of locations an individual can reach given fixed commitments.
Time expanded graph	A graph whose nodes combine time, stop and route, used to route over timetables. See Public transport routing.
Travel potential ($p_{ij}$)	The value of a destination after decay: $f(d_{ij})$.
2SFCA	Two step floating catchment area, a competition corrected accessibility measure.