Final answer:
The only appropriate time to use a cell phone while driving is to report an emergency. Using a phone for any other reason while driving is discouraged or illegal. Hands-free devices may be permitted in some areas.
Step-by-step explanation:
When considering when it is appropriate to use a cell phone while driving, the only time it is considered permissible is to report an emergency, such as a car crash or serious road hazard. Using a cell phone for any other reason, including calling home, or when on an open road with no traffic, is generally discouraged or illegal due to the increased risk of accidents. In some jurisdictions, hands-free devices are allowed, but the safest policy is to avoid using your phone while operating a vehicle unless it is absolutely necessary for an emergency.