This paper discusses the methodology used in the development of advanced traveller information system (ATIS). This system is designed as a part of web geographical information system (GIS) based advanced public transport systems. Web GIS-based ATIS system includes spatial data for the designed functionalities and provides GIS capabilities to the users through the internet. In addition to these functionalities, a route planning algorithm to plan the shortest route between the selected bus transit points is also designed using ant system algorithm and is integrated with web GIS. This study presents the ant system algorithm adopted for the shortest route finding with the methodology developed for the web GIS-based ATIS system for the study area of the city Chandigarh in India using open source software MapServer as web map server. This study also discusses the three-tier logical architecture used in the methodology for providing GIS capabilities to the user over the internet.