快车
kuài chē · HSK 6
bus etc
🚄 快车 = fast + vehicle — the express ride
快 means fast or quick, 车 means vehicle or car. Stack them and you get the fast vehicle — any express service like a bullet train or shuttle bus.
快 — heart radical 忄 + 夬 (phonetic)
快 is a semantic-phonetic compound. The heart radical 忄 carries the meaning, since the original sense referred to a feeling of pleasure or delight. The right side 夬 supplies the sound. The meaning later extended from 'pleased' to 'quick, fast', the dominant modern sense.
车 — pictograph of a chariot/cart
车 is a pictograph originally drawn as a top-down view of a chariot, showing the axle, wheels, and carriage box. The ancient form 車 clearly depicted two wheels connected by an axle. It still means vehicle, cart, or car today.