Using mobile phones while driving can be dangerous as it is mentally demanding, increases reaction time, and reduces the driver's field of view. Research has found that drivers engaged in phone conversations are four times as likely to crash as other drivers, with risks comparable to drunk driving. Phone conversations require mental visualization that takes attention away from the road, and people have difficulty focusing on more than one task at a time. Reaction times are significantly slower for drivers using mobile phones, whether handheld or hands-free.