That's why VTTI and others have disagreed with the National Transportation Safety Board's recent call for an outright ban on cellphone use by drivers. The real problem, they say, isn't talking, it's glancing away from the road.
"Talking on a cellphone and talking to passengers does not increase risk," Klauer says. "But if a driver looks away from the road for two seconds during a six-second period, even if the two seconds aren't consecutive, the risk doubles."
By extension, the issue of visual distraction almost certainly applies to a variety of other electronics now migrating into the vehicle. GPS systems, Internet services, iPods, and complicated center consoles all call for visual contact. The statistical effect is as yet unknown, however, since they're appearing in the vehicle faster than researchers can study them.
For now, though, researchers say they are more concerned about the growing tide of smartphone use. That, they say, is an immediate and very large source of risk.
"We know that people are talking less in their daily communication patterns, but they are typing more text messages and reading more emails," McGehee told us. "That's where the major distraction is."