I'm trying to make a small sensor that would detect a large object coming at me from behind at about 60mph while I'm moving forward at around 7mph. What kind of sensor would I use? I looked up the different types and I found Passive/active infrared, optic-based, piezoelectric, and ultrasonic. I tried to figure it out myself and my best guess is ultrasonic? Like what cars use to detect deer, they use "ultrasonic airflow sensors".
Ideally the sensor would beep and get louder or faster as the object approaches. Thanks!