New Jersey is set to become the second state in the U.S. to ban handheld phone use while driving, joining New York and several dozen other countries, including Britain, Japan, and Israel. Although not yet extended to other in-vehicle systems, these bans provide a dramatic wake-up call for the users of mobile-data applications, not just cell phone users, as well as their employers.

Many jurisdictions both in the United States and elsewhere are getting increasingly tough on the perceived problem of drivers distracted by cell phone usage. This is likely to have repercussions for mobile workers far beyond hanging up on phone conversations. Although legislation to date is mostly narrowly targeted at handheld phone usage, the risks created by divided attention can apply to in-vehicle data systems as well as voice interfaces, not merely to phone conversations. This problem isn't new, but the increasing pervasiveness of mobile IT as well as the growing body of legislation means that many companies need to take a fresh look at the demands they are making on mobile employees.

Academic research increasingly confirms that talking on a cell phone is distracting for a driver to a far greater extent than, for example, a conversation with a passenger. Furthermore, although most legislation so far has targeted handheld phones (for example, the U.K. still permits hands-free conversations using a permanently installed kit), research demonstrates that the problem has far less to do with taking one hand off the wheel and far more to do with the mental load. Consequently, there's little difference between hands-free and hand-held usage. Mentally overloaded drivers are more likely to miss important events on the road ahead, react more slowly to emergencies, and narrow the focus of their attention on the road directly ahead to the exclusion of peripheral events. Research has shown that normally attentive drivers continuously scan the road ahead, checking from side to side and looking in their mirrors. Drivers engaged in other mental tasks, such as conversing or even counting, seem to fix their gaze directly ahead, and the normal scanning stops.

Other research indicates that it's not only voice conversations that can cause problems: data systems that demand concentration also may cause a user to mentally screen out important events. Again, this isn't simply a question of looking away from the road toward a screen: concentration on one task can cause people to miss what is literally in front of their eyes, a situation known as inattentional blindness. This problem was demonstrated most entertainingly by researchers who asked subjects to count passes in a basketball game. A large proportion of participants were so engrossed in the task they failed to notice a man in a gorilla suit wander through the middle of the game, pausing to beat his chest! Consequently, listening to E-mail and dictating responses is likely to be a dangerous practice, too, as is the use of other data systems that require extended interactions.

Perhaps the most insidious element of this problem is that the person who's distracted is likely to be unaware of the problem until there's an emergency. One reason for this is that it's perfectly possible to drive without incident as long as nothing unexpected happens--consequently, few people are aware of how distracted they are. (One example: an early reviewer of a certain in-car navigation system complained that he couldn't adjust the screen to allow the maps to be viewed from the driver's seat, not realizing this was an intentional design point.) It's only when an emergency requiring rapid reaction arises, such as another driver cutting in, or an exit coming up sooner than expected, that slowed reactions or divided attention cause an issue.

Concerned employers should go beyond the bare (and increasingly often legally required) minimum of refraining from asking employees to use a phone while driving. They should recognize that hands-free phone usage offers little improvement, and that other applications that demand extended conscious attention are as problematic as phone conversations. Mentally demanding applications other than navigation aids should be designed to be used when the vehicle is stationary and the driver is safe, or to be used by a passenger rather than by the driver. Where an application must be used in motion--for example, driving directions--design it to provide short interactions or updates, rather than engaging the driver in a long conversation or transaction. Use voice input so the driver can ask for a repeat of instructions or confirmations without taking his eyes off the road.

Distractions while driving are primarily a mental challenge, not a physical one. It's even more important to keep your mind on your driving than it is to keep your hands on the wheel and your eyes on the road ahead. It's not just the law: it's a good idea.

Carl Zetie is an analyst with Forrester Research.

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