Public transport plays a critical role in the sustainability of urban settings. The mass mobility and quality of urban lives can be improved by establishing public transport networks that are accessible to pedestrians within a specific walking distance, which would also reduce monetary and environmental costs. Accessibility to public transport is the ease with which inhabitants can reach means of transportation such as buses, trams, metros, and trains. By measuring the degree of accessibility to public transport networks using a common data format, a comparative study can be conducted between competitive cities or metropolitan areas with different public transport systems. The General Transit Feed Specification (GTFS) by Google Developers allows this by offering a common format for public transportation stops, routes, trips, schedules, and associated geographic information in a series of text files. This paper suggests a method to measure the degree of accessibility to public transit in different urban areas using the GTFS, which is an open-source data set voluntarily produced and shared by the public transit agencies of many participating cities around the world. Functional Urban Area (FUA), which was identified by the OECD in 2013 for global comparative research, was applied as a spatial unit of analysis. Areas a maximum distance of approximately 330m from each bus and tram node, and 660m from each metro and train node, were considered as Service Areas. These Service Areas were then classified into five levels according to operating frequency at each node to assess and compare the degrees of accessibility across FUAs. The analysis was carried out on the route networks of each urban area using ArcGIS 9.3. The results from eight FUAs show that Melbourne and Portland have higher degree of accessibility to public transport.