additional freight; extra fare; surcharge
Refers to an extra charge added to the base fare, often for express services, reserved seats, or special conditions.
When you take the limited express, an additional fare is required.
運賃 is the base fare or freight charge, while 割増運賃 is the extra amount added on top of it.
割増料金 is a more general term for any surcharge, whereas 割増運賃 specifically refers to additional transport fares.
Compound of 割増 (わりまし, 'extra charge, premium') and 運賃 (うんちん, 'fare, freight charge').