Fribourg is on the country's main railway axis, which links Geneva to Zurich. In Switzerland, rail transport is operated by the SBB. In the Canton of Fribourg, the TPF are in charge of most of the public transport services.
Schwarzsee is also easily accessible by public transports.
Take the train to Fribourg, from where the bus , operated by TPF, takes you to Schwarzsee.
SBB
The Swiss Federal Railways (SBB) serve most of the major transport axes in Switzerland. You will find timetables for nearly all of Switzerland's public transport on the SBB website.
TPF
Transports Publics Fribourgeois are the main transport providers in the Canton of Fribourg. The TPF are in charge of urban public transport in the town of Fribourg, as well as most of the bus connections in the Canton and several railway lines.