Safest Proximity Sensor type for use in public: RF vs IR vs Ultrasonic

Sensors Distance
1

I have a WIP project for a proximity-sensor to drive a motor for motion tracking…

Expected range will be ~1m to 5m+

Desired update & motion response ~.5 seconds (somewhat ‘twitchy’)

This will be in a public space, so exposure to passers-by is also an important consideration

Which would be the better instrument to go with between IR, RF, or Ultrasonic?

2

None of these are inherently dangerous at reasonable power levels. For example, most nanny cams use infrared LEDs for nighttime illumination. Ultrasound for medical imaging is common. A lot of modern cars use radar for blindspot monitoring.