Final answer:
The legal time to use a cell phone without a hands-free device while driving is when calling for emergency assistance. Using a hands-free device minimizes distractions and is typically required even when stopped at a red light, unless it's an emergency.
Step-by-step explanation:
It is generally legal to use a cell phone without a hands-free device while driving only when making a call for emergency assistance. Laws vary by jurisdiction, but typically this is the only time it is allowed for safety reasons. Even when stopped at a red light, drivers are usually required to remain attentive to the road and should use a hands-free device if they need to make a call.
However, during an emergency, such as if a passenger is in urgent need of medical help, drivers are permitted to use their phones to seek assistance. It is essential to remember to use hands-free devices to minimize distractions and increase safety when making calls in non-emergency situations.