Rob Bennett for The New York Times

Updated, July 21, 12:01 p.m. | On Tuesday, two consumer advocacy groups, using the Freedom of Information Act, made public for the first time federal research about the serious and growing threat of cellphone use on America’s roadways. The research was for a study by the National Highway Traffic Safety Administration that never happened in part because of concerns about angering Congress.

An increasing number of studies show that driving while talking on a cellphone can be dangerously distracting. Yet most states have not barred handheld phones, and none have banned all drivers from using hands-free devices. (Half a dozen states and the District of Columbia prohibit driving while holding a phone; currently 14 states and the District of Columbia ban texting while driving.)

Some opponents say cellphone bans are simply not enforceable. Others argue that drivers do all sorts of distracting things while driving — like eating, arguing with kids in the back seat, listening to music — so it makes little sense to outlaw one activity.

We asked several experts how significant is the cellphone hazard? As a matter of public safety, should all cellphone use while driving be banned?

Education, Backed by Law

Janet P. Froetscher is president of the National Safety Council.

More than 50 research studies have reported the risks of cellphone use while driving. Talking on a cellphone while driving makes a person four times more likely to be in a crash. This is a much higher risk than most other distracting activities, including eating, drinking, reading billboards, listening to the radio, or talking to other passengers. It’s the cellphone conversation that diverts people’s attention from the road.

The National Safety Council has called for a total ban on cellphone use while driving because more than 100 million people are engaged in this high-risk activity every day. We do not support laws that would permit the use of hands-free devices, because there is no scientific evidence that those devices are any safer for drivers.

Hands-free-only laws send the wrong message and may actually encourage more unsafe behavior.

In fact, hands-free-only laws tend to send the wrong message — that drivers can safely talk on phones without getting into crashes. And such laws may actually do harm, if drivers, lulled into a false perception of safety, start using hands-free phones to make more calls and talk longer.

Some argue that the cellphone laws are not enforceable. But many law enforcement officers involved in the setting of our policy don’t agree. There are various approaches available, and there are some good models to follow.

For example, a “high visibility mobilization” strategy — letting drivers know laws will be enforced — has been developed to enforce drunk driving, speeding, seat belts, child safety seats and graduated licensing for teens. With this approach, several times each year, people are informed that law enforcement is paying special attention to a particular law.

Read more… These programs are designed to increase compliance with a law, not to write more tickets. The science is clear: high visibility mobilizations can cause people to change their high-risk behavior and comply with the law. The same model could be use to increase compliance with cellphone laws. Laws, of course, are not the only way to address this problem. Educating people about the risks and the science is also important. Verizon Wireless, one of the major carriers, does this well on its Web site: “For your well being and the well being of those around you, you should consider turning your phone off and allowing calls to go to Voice Mail while you are driving.” That message needs to go mainstream.

Total Bans May Be Impractical

David Champion is director of automobile testing at Consumer Reports.

There is no question that talking on a cellphone while driving is a dangerous distraction. The issue that has caused much debate is the magnitude of the distraction. Many studies have shown that the level of distraction has more to do with the intensity of the conversation and not whether the phone is hand-held or hands-free. An in-depth conversation that requires a good deal of thought causes a higher level of distraction than a relatively short “Can you pick up milk on the way home, Honey” type of call.

Both the length and intensity of the call increase the risk of a crash. The longer the call or the more in-depth or emotional the conversation is, the more the driver concentrates on the call rather than on his or her driving.

Why not make the punishment for crashes caused by cellphone use extremely high?

According to a study by the University of Utah cellphone users drive slower, pass less often and take longer to get to their destination. Compared with undistracted drivers, those who used cellphones drove an average of 2 miles per hour slower. This is a good sign, but even driving slowly can cause accidents because annoyed drivers who are being held up may drive recklessly to pass the cellphone user.

Whether it’s talking on a cellphone, eating or drinking, adjusting the radio, or programming your navigation system, increasingly, it seems that driving is not always the top priority in the car.

Read more… Data from the National Highway Traffic Safety Administration’s 100-Car Study indicated that if a driver takes his eyes off of the road for more than two seconds, it greatly increases the risk of a crash. Together with the intensity of the conversation, cellphone use is becoming a major cause of road crashes and fatalities. Texting while driving raises this level of risk exponentially. Ultimately, if the studies show that talking on a cellphone provides the equivalent impairment of having a blood alcohol level of 0.8 — the limit to drive a car in most states — the use of cellphones while driving should be banned. This is probably an impractical solution, but since other restrictions all have their own issues, the best solution in the near term is to warn drivers with public service announcements of the risks involved with cellphone use and make the punishment for crashes caused by cellphone use extremely high.

Let People Dial While Driving

Katherine Mangu-Ward is a senior editor at Reason magazine.

In 1995, 13 percent of the U.S. population owned a cellphone. Today, cellphone ownership rates are well over 80 percent. In those 14 years, the annual number of motor vehicle deaths has remained eerily constant, hovering around 40,000.

We must resist the impulse to pass a bunch of new laws that simply satisfy our need to do “something.”

These tidy numbers don’t prove that driving while simultaneously talking to your mom and texting your sister is a brilliant, risk-free idea. (Perhaps that figure could have been lower.) But the facts do suggest that the rise of the killer cellphone — and the corresponding need for government intervention — has been exaggerated. As strong as the impulse may be to pass a bunch of new laws in order to satisfy our need to do “something,” we must resist.

The human brain is a funny, quirky thing. We’re not great at estimating risk, especially at the extreme ends of the scale. A few news stories about tragic texting deaths, plus a new brain study or two, and we start to lose track of where cellphone use fits on the risk scale. Rubbernecking, or “looking at an external object,” triples your risk of being involved in a crash or near crash — about the same increase as dialing a phone. “Reaching for a moving object” — a kid, say increases the risk by nine times. Yet there is no clamor to ban mobile parenting.

Read more… We humans are also notably bad at comparing concentrated costs with diffuse benefits. It’s easy to tally up the costs of dialing while driving — there are accident reports and mortality figures. But it’s much harder to add up all the benefits. Think of every carpool disaster averted, grocery list amended, or stress-relieving traffic update made possible by the use of cellphones in cars. Think of every kid who got through to his mom, every long-distance relationship maintained, every roadtrip rescued. True, these aren’t matters of life and death, but billions of tiny gains in happiness and reductions in stress are too often overlooked in public policy debates.

The Trouble With Cellphone Laws

Anne McCartt is senior vice president for research at the Insurance Institute for Highway Safety, a nonprofit research organization funded by auto insurers.

It’s clear that cellphone use while driving increases crash risk. But it’s far from clear that laws prohibiting all cellphone use behind the wheel will have much effect on driver behavior.

Research now links talking on a cellphone to a greater likelihood of crashes. A 2005 Institute study of drivers in Western Australia found cellphone users four times as likely to get into injury-producing crashes. The study, using cellphone billing records to verify phone use of drivers, found that the increased risk was similar for males and females, drivers younger and older than 30, and hands-free and hand-held phones.

If officers can’t readily see whether a driver is using a phone, they can’t enforce the law vigorously.

The problem is making laws banning cellphone use effective. In New York, which enacted the first ban on handheld cellphones in 2001, drivers’ use of such phones went down by about 50 percent shortly after the law took effect. But this decline had dissipated substantially when measured a year later. The result was different after a similar law was enacted in Washington, D.C., where use also declined by about 50 percent and the decline was sustained a year later. More intensive enforcement in Washington could be a reason for the difference.

Evidence is mounting that conversations on both hands-free and handheld phones lead to similar declines in measures of driving performance. There may be advantages of hands-free devices in placing the call, but the cognitive distraction of the conversation remains with a hands-free device.

Read more… Based on this evidence, it makes the most sense to ban the use of any type of phone. But it’s difficult to enforce a hands-free ban, because officers can’t readily see whether a driver is using a phone. And without strong enforcement, behavior won’t change. The record high rate of safety belt use in the U.S., for example, is the result of states enacting belt laws and vigorously publicizing and enforcing them through the Click it or Ticket program. Drivers using phones have to believe there is a high likelihood that they will be stopped and ticketed. Absent tough, sustained, and highly visible enforcement, laws are unlikely to have much effect in convincing motorists to put down their phones.

How the Brain Reacts

Marcel Just is the D.O. Hebb Professor of Psychology and director of the Center for Cognitive Brain Imaging at Carnegie Mellon University. Tim Keller is a senior research psychologist at the center. They are co-authors of the study, “A Decrease in Brain Activation Associated With Driving When Listening to Someone Speak.”

Behavioral studies have shown that talking on a cellphone diverts the driver’s attention and disrupts driving performance. We investigated that question by looking at brain activity that occurs during driving. In our study, using functional magnetic resonance imaging (fMRI), we examined the effect of listening to someone speak on the brain activity associated with simulated driving.

Center for Cognitive Brain Imaging, Carnegie Mellon University

Participants steered a vehicle along a curving virtual road, either undisturbed or while listening to spoken sentences that they judged as true or false. The parietal lobe activation associated with spatial processing in driving decreased by 37 percent when participants concurrently listened to the sentences. We found that listening comprehension tasks drew mental resources away from driving and produced a deterioration in driving performance, even though the drivers weren’t holding or dialing a phone.

These brain activation findings show the biological basis for the deterioration in driving performance (in terms of errors and staying in a lane) that occurs when one is also processing language. They suggest that under mentally demanding circumstances, it may be dangerous to combine processing of spoken language with a task like driving a car in demanding circumstances.

Our listening experiment did not require the participants to speak, so it was probably less disruptive to driving than an actual two-way conversation might be. It’s likely that our study actually underestimates the reduction in driving performance.

Read more… If listening to sentences degrades driving performance, then probably a number of other common driver activities — including tuning or listening to a radio, eating and drinking, monitoring children or pets, or even conversing with a passenger — would also cause reduced driving performance.

It would be incorrect, however, to conclude that using a cellphone while driving is no worse than engaging in one of these other activities. First, it’s not known how much these other distractions affect driving (though that would be an interesting study). Second, talking on a cellphone is a particular social interaction, with demands different from a conversation with a passenger. Not responding in a cellphone conversation, for instance, can be interpreted as rude behavior. By contrast, a passenger in a car is more likely to be aware of the competing demands for a driver’s attention. Indeed there is recent experimental evidence suggesting that passengers and drivers suppress conversation in response to driving demands. Third, with spoken language, a listener cannot willfully stop the processing of a spoken utterance. These considerations suggest that talking on cellphones while driving can be a risky choice, not just for common sense reasons, but because of the way our brains work.

Cellphone Use as a Moral Issue

Tom Vanderbilt is the author of “Traffic: Why We Drive the Way We Do (and What It Says About Us).” He writes the “Transport” column for Slate and blogs at How We Drive.

Human attention is imperfect and prone to gaps under the best of circumstances. In a well-practiced task like driving, it is virtually impossible to assume, much less legislate, that an individual will always devote sufficient attention.

That said, the science is growing increasingly conclusive that a cellphone conversation — whether hand-held or hands-free — exacts a toll on things like reaction time and hazard detection; that these conversations quantitatively differ in their effects from other forms of in-car distraction (including talking to a passenger); and, perhaps most important, we are not fully able to gauge exactly how distracted we are.

Since driving is the only thing most of us do that can cause the loss of someone else’s life, isn’t it wrong to compromise our driving ability?

And texting while driving, which emerged so quickly as an activity that the science is still catching up, is even more insidious, compromising not only one’s mental workload, but requiring many more glances away from the road.

In an ideal world, we wouldn’t need a law banning such activities — rather, they would be simply common-sense measures taken by the operators of heavy industrial machinery (which, despite the marketing messages that car companies put out, is what driving is). As the late visionary Dutch traffic engineer Hans Monderman put it to me a few years back, “There are so many things that can be forbidden. The stranger thing is that we believe everything that isn’t forbidden is allowed.”