You often hear that cellphones are a distraction in the car for a number of reasons, from people looking down to read a text or reaching to pick up a phone that has fallen and taking their hands off of the wheel.
Sometimes, people think that avoiding these specific issues means phone use is safe in the car. It may be safer, as it is clearly better to be watching the road while talking than looking down and texting, but any phone use can be problematic.
The issue is with the brain's cognitive load. This is simply the amount of work it can do at one time, or the amount of mental activity you can handle. This is a finite amount.
When you divide your attention, you increase the mental demand. Instead of just driving, you now have to think about driving and the conversation you're having. You are also subconsciously thinking about holding your phone close to your ear. You are trying hard to listen to what the other person is saying, but you're also formulating responses and thinking through the meaning behind their words.
By taking brain power away from driving, your ability to drive decreases. You're less observant. You make small mistakes, like drifting in your lane or increasing and decreasing your speed. In the worst cases, you overlook a critical factor -- like a stop sign that is slightly hidden by bushes or parked cars -- and cause an accident.
Have you been hit by another driver who was distracted at the time? If so, you must know what rights you have to financial compensation.
Source: Psychology Today, "The Truth About Texting and Talking While Driving," Ellen E. Pastorino, accessed April 13, 2018