Travel Time Information Using Global Positioning System and Dynamic Segmentation Techniques

Abstract

The architecture and application of an updated methodology based on the Global Positioning System (GPS) for conducting travel time studies are described. The methodology is called Travel Time with GPS (TTG). TTG uses a general data model that includes a spatial model, a geographic relational database, and a procedure for linearly referencing GPS data using dynamic segmentation tools. This architecture allows users to conduct travel time studies at various levels of resolution (from regionwide studies down to studies of signalized intersections). The data reduction and data reporting for such a system are outlined. Data reduction is based on linear referencing of GPS data using highway links, where highway links are defined as vector representations of directional centerlines delimited by physical discontinuities. Data reporting is based on the use of dynamic segmentation tools to compute travel time and speed along highway corridors using any highway segmentation scheme. The resulting aggregated data can be used for the production of tabular reports and color-coded maps to document travel time, delay, and speed data. The database management system built into TTG allows users to handle many GPS data files using a centralized, structured procedure, which is critical for data archival purposes and the development of clientserver applications. In conclusion, quantitative values for data storage requirements and processing speeds are provided. Those values should be useful to practitioners currently designing travel time information systems.