Relative Reachability Analysis as a Tool for Urban Mobility Planning - Position Paper.

There is a plethora of user-oriented route planning applications and systems that enable the computation of the fastest journey between two locations using different transportation modes, e.g., car, public transport, walking, bicycle. While useful for individuals, they are of limited interest to a class of users that may be interested in a more global and comparative view of transportation systems in general. In this context, we adopt the view of an urban planner. Urban planners may be interested in queries such as "if a new transit stop was to be introduced in a given location, would that bring the travel time to a given point-of-interest (POI) or area-of-interest (AOI) by bus closer to the travel time by car, therefore improving air quality and/or overall traffic congestion?" To answer queries such as this one, as well as many other interesting ones, we propose the concept of relative reachability which aims at measuring how efficient a given transportation mode is (or may be) in comparison to other competing modes. We discuss the challenges associated with the computation of relative reachability of POIs (or AOIs) within a city, which reveal directions for interesting research in spatial data management towards better informed urban mobility planning processes.