When is it legally acceptable for a taxi or rideshare driver to interact with their digital dispatch device or GPS screen while driving?

1. At any time, as commercial drivers are completely exempt from distracted driving laws
2. Only when the device is securely mounted, and the driver can use it with a brief touch or voice commands without distracting from driving
3. Only when driving on high-speed highways where steering is minimal
4. Only when looking at the screen for less than 15 seconds at a time