The correct import of public transport data from other systems is an important basis for building and updating a multimodal transport model.
The integration of the data into an existing transport model poses two major challenges.
1. The data must first be formally converted to fit into the Visum data model. This results in a georeferenced Visum network model that contains only the public transport data from one data source. The role of this formal transformation is taken over by the specific public transport data importers, which serve proprietary and standard formats (GTFS, HAFAS or VDV 452). The transfer of as much information as possible is advantageous, as it simplifies subsequent processing. Especially route points between the stop points, as they are available in the shp files of GTFS or in the realgraph of HAFAS, help with the later merging of the models.
2. In a second step, this Visum data must then be merged into an existing transport model.
Since a Visum version file already exists after the first import step, the specific interpretation of the data is not necessary. Data from operative planning systems are often available based on an operating days (Fundamentals: Valid days). In Visum a valid day based modeling is preferred.
After the import of timetable data based on operating days, there are often many identical vehicle journeys in Visum that only differ in their validity. With the function "Aggregate vehicle journeys", identical vehicle journeys are combined. Identical vehicle journeys are vehicle journeys with the same time profile and the same timetable situation. Their validity is combined in one valid day. To reduce the number of resulting valid days, operating periods are generated and the valid days are normalized.
Imported line blocks cover only one operating day and do not have to be closed. A block version is inserted for each operating day. If you want to convert these line blocks based on valid days, these individual block versions have to be merged. In this case, the individual line blocks must be adjusted to achieve an optimum combination. For example, additional empty trips or time overlaps to be inserted are evaluated negatively. The result of such a combination of block versions is a new block version that combines the selected versions.
The integration of the vehicle journeys and line blocks into an existing transport model, which usually has a different network base, is carried out by the function "PuT supply from Visum..." (PuT supply import). The stops are referenced and the line routes, time profiles, and vehicle journeys are transferred by means of intelligent map matching. Transport systems and valid days are merged after import and line blocks are transferred.
