A data model for managing GPS travel time data

Travel time studies are widely used to document congestion and to quantify the impact of highway improvements. Global positioning system (GPS) receivers can be used to survey the location of landmarks and to automatically record the speed and location of probe vehicles. However, GPS receivers record location in latitude, longitude pairs. They also tend to produce files having huge numbers of records, particularly if data is collected at short intervals, say every one second. In order to access this data it is necessary to store all GPS point data in a database and provide a linear reference to each GPS point. This paper describes a data model that can be used to map GPS travel time data to a GPS-based highway network. The data model includes a general spatial model, an appropriate geographic relational database schema, and a procedure for linearly referencing the GPS data. The paper also discusses data reporting procedures.