Scope
A journey planner finds one or more suggested journeys between an origin and a destination. The origin and destination may be specified as geospatial coordinates, named topographical places (e.g. 'Timperley', 'Scunthorpe', 'Grimsby' ), Points of Interest e.g. 'British Museum', or names or identifiers of points of access to public transport such as bus stops, stations, airports or ferry ports. A location finding process will typically first resolve the origin and destination into the nearest known nodes on the transport network in order to compute a journey plan over its data set of known journeys.
Journey planners for large networks typically use a search algorithm to search a graph of nodes (representing access points to the transport network) and edges (representing possible journeys between points). Different weightings such as distance, cost or accessibility may be associated with each edge.
Searches may be optimised on different criteria, for example fastest, shortest, least changes, cheapest. They may be constrained for example to leave or arrive at a certain time, to avoid certain waypoints, etc.
- Also known as a "Trip Planner", a Journey Planner may cover a single mode of transport, e.g. rail, or many transport modes for a combined journey, e.g. bus rail, air, in which case it is an Intermodal Journey Planner.
- A Road Route Planner is a journey planner specialised for road network use. Road networks are characterised by a large number of nodes and edges which may typically be used at any time.
- A Public Transport Journey Planner (or in American English usage, a Public Transport Route planner) is specialised for journeys on Public Transport. A public transport network is characterised by a smaller graph, with services that typically run only at a particular time or at a specified frequency.
Historically a Route planner has covered just the Route, showing a path by which it is possible to travel between two points at any time; in contrast a Journey Planner has also take into account the timetable of services that run over the network only at certain times, and so the time of travel is relevant when computing a journey. However with the development of "road timetables", associating different journey times for road links at different times of day, time of travel is also relevant for road route planners.
Read more about this topic: Journey Planner
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