text: Cell phone use behind the wheel shortens brain activity with driving. Typing text messages shortens a driver's ability to direct attention to the road, and react to traffic situations. People shouldn't fully depend on cell phones while they are in their cars because they are not reliable. Therefore, nowadays cell phones are unnecessary devices in your vehicle because you should give your full attention to what's around you. It's safer to use a hands free device so you won't have to reach for your phone, or connect a watch to your phone so all your texts and calls would come through.