Kāichē fànkùn de shíhou, yídìng yào tíng xiàlai xiūxi.
If you feel drowsy at the wheel, you must pull over and rest.
Tips
usage
犯 here means "to have an attack of" something unwelcome that keeps coming back, as in 犯病 "to fall ill again" and 犯愁 "to start worrying". 困 alone is the state, as in 我困了 "I'm sleepy"; 犯困 is drowsiness coming on, usually at the wrong time.
