The majority of transit trip planners exist as proprietary systems based on particular vendor products. With the incorporation of more functional components, system maintenance and regular transit information updates become burdensome tasks for transit agencies. In addition, the proprietary nature of the systems makes it difficult to take advantage of the rapid advancement of geospatial information and web technologies. The authors proposed an open and interoperable transit trip-planning system based on a service-oriented architecture, with the principle of reusing the existing modular resources, while providing user-friendly interfaces for expansion of functionality. The objective was to integrate geospatial services available onl...