What must you anticipate with this road sign?

This traffic sign warns of low-flying aircraft or an airport nearby. When you see it, you must expect sudden aircraft noise. Such noises can distract you or other road users, which may lead people to respond unpredictably—like braking suddenly or not paying full attention. That's why all three answers are correct: sudden airplane noise, distracted road users, and vehicles that might brake unexpectedly are all possible in these areas. Always stay alert and maintain a safe distance when you see this sign.