Driving while using a handheld device can reduce a drivers response time just like a drink driver. Also, over half of high school drivers use their phones while driving, and some of them think it's safe, but it's clearly not. People get more distracted when preparing to speak than when they are listening, and this can lead to many deaths on the road.
Driving an automobile already requires an immense amount of concentration and attention. While undergoing auto education, there's a specific section in the curriculum that focuses on auto accidents due to distractions while driving. They list loud music, conversations, food, and most importantly cell phones. They detract a significant amount of attention from driving, and with their fast-growing list of applications, cell phones have become increasingly hard to navigate without full attention. This simply spells danger in an already dangerous situation.
People who use their cellphones and drive are not only a danger to themselves but also to everyone else on the road with them. People that use their cell phones are not focused on driving and as a result can turn into oncoming traffic or not apply the breaks in time. Even while using hand free headsets the drivers attention is still not on driving.