Drivers have long tried to manage any number of distractions ranging from eating a snack and reading a map to dealing with unruly children in the backseat and putting on makeup. But with the increasing popularity of cellphones and texting, distracted driving has emerged as a central concern of safety experts. Studies indicate that distractions are involved in more than 5,000 traffic fatalities every year. Most states have enacted laws to restrict texting or talking on handheld cellphones, and policymakers face calls for a near-total ban even on hands-free communications devices — including those that are built into the dashboards of new cars and heavily marketed by automakers. But even if more restrictive laws were passed, many motorists would find it hard to set aside the devices they have come to rely upon to make business and personal calls and also to check websites or update their Facebook pages.