When is it illegal to use a cellphone while driving?

Using a cellphone while driving becomes illegal when it interferes with the safe operation of the vehicle. This is because any distraction, including using a cellphone for texting, calling, or navigating, can impair a driver's ability to focus on the road, respond to changing traffic conditions, and make timely decisions. The law is designed to promote safer driving by minimizing distractions that could lead to accidents, protecting both the driver and other road users.

In contrast, using a cellphone while parked does not pose a risk to safety, and having passengers use their phones does not inherently distract the driver if managed correctly. The law does not specify restrictions based on the time of day, so night driving alone is not a factor that makes cellphone use illegal. Ensuring focus on driving should always take precedence, regardless of the context.