When is it legal to use a cell phone while driving?

Using a cell phone while driving is legal when employing hands-free devices because these allow drivers to maintain better control of the vehicle and keep their focus on the road. Hands-free devices minimize the need to physically handle the phone, which can reduce distractions. Many states recognize that hands-free technology helps in mitigating some of the risks associated with using a phone while driving.

The other options highlight scenarios that either restrict or don't accurately represent current legal standards in many jurisdictions. For instance, using a cell phone only when the car is parked suggests that there are no circumstances under which phone use is allowed while driving, which is not true when using hands-free methods. The suggestion that it is legal anytime as long as it is not distracting overlooks the specific laws that many states have regarding the use of phones. Finally, mentioning federal law doesn’t apply as there are state laws specifically concerned with mobile device usage while driving, making them more relevant in determining legality.