Seoul's "Climate Card," offering unlimited public transit rides for a fixed monthly amount, went into operation on a trial basis on Saturday.

Cardholders could use them from Saturday's first bus at four in the morning. They could also use them on subways, buses, public bicycles, and other means of public transportation.

However, since cards don't yet work in Gyeonggi Province and Incheon areas, even if users take a bus or subway in Seoul, they can't get off a stop or station outside the city.

In such instances one must call a station or stop manager and pay an additional fare.

Plastic cards can be purchased at information centers or nearby convenience stores on subway lines one to eight. Android users can also use a mobile app.