Every time a legislator submits a proposal to ban the use of cell phones while driving, opponents rise up to attack the bill as onerous and ineffective.

“What’s next?” they say. “If we ban cell phones because they’re a distraction, then we might as well ban every other driver distraction, too, such as eating, combing your hair and fiddling with the buttons on the car radio.”

Which is exactly what would happen if the Legislature approves LD836, otherwise known as “An Act to Prevent Distracted Driving,” which was recently approved by the Transportation Committee. The measure would prohibit a person from doing anything behind the wheel, in other words, that might impair the ability to complete the crucial task of getting a vehicle safely from one place to the next. The distractions might include using a cell phone, eating, reading, grooming oneself or any creative combinations thereof.

While driver distraction is one of the leading causes of crashes in the country, the enforcement section of this bill is about as vague as any driving-related legislation to come down the pike in the last few years. A police officer, the bill says, “may enforce this prohibition only if the officer has detained the operator of the motor vehicle for a violation of another law.”

The more I read that part, the muddier it gets.

Imagine that you have just pulled away from the McDonald’s drive-through and into the flow of traffic with a Big Mac in hand. Having performed this feat a hundred times before, you feel quite confident in your ability to nibble a sandwich without losing your focus and crashing into a telephone pole. But now imagine that you get pulled over for having expired license plates or for improperly changing lanes. Considering the unspecified language of the bill, does the officer then have the authority to bust you for distracted driving, too, based on the prima facie evidence lying half-eaten in your lap? Or perhaps for the travel mug of coffee in the holder, or the used dental floss on the dashboard, or the opened book on the seat beside you?

Is it possible to be nailed, let’s say, for driving and chewing bubble gum at the same time?

The way I see it, the bill appears to be an attempt to address the dangers of driver distraction without singling out the ubiquitous car phone as the primary culprit. Not only does lumping all distractions into one bill make enforcement a guessing game at best for police, it fails to confront the obvious fact that yakking on a phone while doing 70 on the highway is in a high-risk category all its own.

The same Transportation Committee that recently rejected a car-phone ban for the general driving population wisely included one in its list of proposed restrictions for youngsters driving with provisional licenses. The reasoning, it would seem, is that only veteran drivers are capable of safely juggling phone conversations and the demands of rush-hour traffic at the same time.

The New England Journal of Medicine takes the broader view that car phones are an equal-opportunity distraction, no matter the age. Its 1997 study determined that concentrating on a phone conversation while driving is nearly as risky as driving while legally drunk. Reaction time is slowed significantly, the journal reported, when the mental focus necessary for safe driving is being channeled instead into concentrating on a phone call about a crisis at home or at work.

The Journal of Experimental Psychology: Applied, in reporting a study conducted last year at the University of Utah, referred to this mental disconnect as “inattention blindness.” Researchers tested the reactions of 100 people who used sophisticated driving simulators while making calls on cell phones. Results showed that people on phones drove sluggishly, decreasing their speed as the car in front pulled farther away. But when the car in front braked in heavy traffic, several of the simulation drivers didn’t even see the vehicle and plowed into its rear end.

They also looked directly at highway signs without being able to recall later that they had even seen them. Drivers who didn’t use cell phones, on the other hand, experienced no such dangerous disconnection between the brain and eye.

If our lawmakers are unwilling to ban phone conversations while driving, they could do us all a favor by killing off this well-intentioned but unworkable bill entirely. It’s just another distraction from the more serious safety issue, and we obviously have enough of those already.