Finnish Transport Infrastructure Agency's Open API's
FTIA aims to make the use of open data as easy as possible. At this site users can find information on open API's and open source applications.
Suomen Väylät -mapservice
Open data for road, railway, and waterway network can be accessed through the Suomen Väylät -mapservice.
An educative video on how to access open infrastructure data (in Finnish only)
Data distribution service
FTIA also maintains a service for sharing open data files that are of large size (AVA). Via the AVA service users can download, for example, road network and Digiroad data from whole Finland as ZIP-files. Go to AVA service.