Cell phones while driving: hands free doesn't mean risk free

Don't ask me why I am so fixated on this topic but whenever I see an article about driving and cell phone use I post on it (example here). The idea that talking on the phone, dialing or texting while driving might be a wee bit of a cognitive problem doesn't seem too controversial, but many people think that the "hands free" version gets around the dangers. The little work that has been done on that subject suggests otherwise. Does that mean that just talking to another passenger is just as bad? Apparently not:

Hands-free mobile phone calls are significantly more distracting than even the most talkative passenger, a new study by US psychologists has found.

It is the latest in a line of studies calling into question the safety of hands-free devices for drivers. Previous research in Australia found that using them while driving is just as dangerous as talking on a regular cellphone, increasing the risk of crashing by a factor of four. (New Scientist)

David Strayer and colleagues at the University of Utah's Applied Cognition Laboratory have been studying phone use while driving using a driving simulator for some years. In a paper in press at the Journal of Experimental Psychology: Applied they studied 96 drivers, aged 18 to 49 year old. Using a hands free phone resulted in straying out of their lanes and missing exists more frequently than when they carried on similar conversations with a passenger in the car. This seems kind of odd and the explanation isn't completely clear. Strayer's explanation is that passengers add cognitive value, or at least take less of it away:

"When you take a look at the data, it turns out that a driver conversing with a passenger is not as impaired a driver talking on a cellphone," says Strayer. "The passenger adds a second set of eyes, and helps the driver navigate and reminds them where to go."

What's more, passengers simplify or slow their conversation in response to conditions on the road. "The difference between a cell-phone conversation and passenger conversation is due to the fact that the passenger is in the vehicle and knows what the traffic conditions are like," he says.

There is certainly value to having a phone in the car in the event of emergency. Under certain circumstances it can save money and lives. But I know too many people who fill up their commute times by calling friends and family as they whiz down the highway at 100 feet per second. And they are sharing the road with me. That scares the crap out of me.

And I know I'm not the only one.


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Interesting. I'm pretty sure I've heard suggestions that talking on the phone is worse than talking to a passenger, but never seen it demonstrated this clearly before. As you say, it does seem a little odd...

I wonder if the cognitive load of talking to an essentially "imaginary" person is perhaps heavier than talking to someone who's actually there? I ask this because I find I can do other things whilst talking to someone who's there in person quite easily, but if I try that when talking on the phone, I tend to forget that I'm on the phone. It can lead to all sorts of awkwardness when phone conferencing... ;)

I don't drive, but being a pedestrian and cyclist has gotten me into the habit of paying attention to everything that's going on on the road. Once I was riding with somebody from out of town, and was giving a running commentary about various things we were driving past; after she missed a sign, I added navigation and road conditions to what I was talking about. She seemed surprised that somebody who doesn't drive would pay that much attention to what was going on.
But anyways... the point that was meant to illustrate is that it seems perfectly obvious to me that somebody in the car is going to be less distracting than somebody on the other end of a phone connection; I'm probably an extreme case, but a passenger knows what's going on outside the car, and knows when to shut up and let the driver focus on driving, which is information the person on the other end of the phone doesn't have.
(It would be interesting to see how kids in the back seat compare to adult passengers and cell phone conversations; I'd guess closer to the cell phone.)

I've seen this claim before (including the 'passenger is another set of eyes' bit) and find it highly questionable (note that these tests are in simulators, which are hardly representative of real world situations including fatigue). I can hardly imagine that the powerful instinct for eye contact with the passenger does not have a very negative effect on road attention.

Other studies based on accidents have concluded that children and eating in the car are one of the major distracting influences

jayh: I don't think there is any argument that there are other distractions for drivers. Even being alone can be a distraction because I often am thinking about science when I am driving alone. The question here is which distractions are more important and which ones can we do something about. No one would argue that texting while driving isn't more dangerous than talking on the phone. So there are degrees of distraction and simulators can help in figuring out which ones are more troublesome and maybe why. The argument isn't whether simulators are or aren't the same as driving. They aren't.

Anecdotal evidence doesn't count--except that it does in the real world. The rate of people driving badly has skyrocketed with the introduction of cellphone technology. It's freakin' awful out on the roads now. People have been driving with children in their cars for years. They've been eating in their cars for years. It's the cellphones that have turned simple commutes into a demolition derby.

Driving while on a cell call should be flat out illegal.

I did not get a cell phone 2002 or so (somewhat unique for my age group) and had observed bad driving and cell phones for a while. I was determined not to be a bad or inconsiderate driver when I got a cell phone and got a hands free set-up.

I had to do more driving than usual (for me) in that period (250-350 miles a week) and decided I would use the time better to call people especially when traffic was light. One night I had a 20 minute phone conversation at the end of which I realize I could not remember anything about the road/traffic conditions for the last 15 miles or so. It was then I realized that this was a problem for me and started seeing some research stating the same. I seldom use my cell phone when driving and when I do I make sure it IS NOT hands free as I need to be reminded that I should not be on the phone and driving. Luckily I live in a densely populated area where attentive driving is mandatory so I am not tempted to use the cell phone.

Other people make very different choices and what strikes me is how unapologetic people are about driving with cell phones. The same people who would scream about risks 1000 times less if they were imposed on them.

By floormaster squeeze (not verified) on 03 Dec 2008 #permalink

Using a cell phone definitely impairs my driving in a way that I can actually feel, in the form of a sort of cognitive fog. It's more like driving while drowsy or on, say, Benadryl. Talking to a passenger (or eating, or fiddling with the iPod or the air conditioning), not so much.

I don't think this is correct, though:

"The passenger adds a second set of eyes, and helps the driver navigate and reminds them where to go."

That makes no sense to me at all. Assuming that we're not electromagnetically scrambling our brains in some way, I'd say a larger part of the problem is that voices on cell phones are harder to hear clearly; even when the reception is good, they're lower in volume and tinnier, so it takes more concentration to decipher what people are saying.

As a comparison, I have a fair amount of music and speech recorded on cylinders circa 1900. I've been listening to it long enough that I can usually make the words out, despite the noise and the poor frequency response. But for friends of mine who aren't used to it, it just sounds like static; they really have to concentrate to pick the words out. I suspect that the bad sound of cell phones is at least partially to blame for their cognitive effects.

Anyway, I've found that seven times out of ten, when people tailgate me on the freeway, they're on cellphones. You can always spot 'em because when you switch lanes, they don't speed up to pass you. That said, I'm probably more worried by the people who use cellphones while driving on city streets. There's usually a bit more margin for error, and fewer distractions, on the freeways.

We could outlaw electronic billboards too, for all I care.

All cell phone use should be illegal while driving, no and, if or buts about it. I am probably considered a dinosaur as we don't have cell phones, did when they first came out but quickly realized the distraction and disruptions they caused in our lives and others. Just didn't want to be a part of all that.
If there's an emergency then I'll have to rely on the goodwill of another person or just plain deal with it.

Utah local news talked about this awhile back and they showed pictures of people on the road with cell phones. There was absolutely zero eye contact with pedestrians and other drivers. You think Los Angeles has bad drivers, come to Utah.
Sometimes I drive through a heavy truck distrubtion area to get to my MD, I've seen numerous times semi drivers on the cell, going around curves, making left hand intersection turns.

I'm with you revere, it scares the crap outta me.

You think Los Angeles has bad drivers, come to Utah.

Was just there last week, and I have to agree. Took a steep, winding road from I-70 to I-15, and SUVs were tailgating each other at about 75mph. On a rainy night, no less. With lots of patches of road construction. Completely terrifying.

I shudder to think how many of 'em were chatting on the phone.

Driving while on a cell call should be flat out illegal.

It's illegal here in Utah, but nearly everyone I know does it, and I often times see drivers doing it as I cross intersections.

That's just dandy llewelly as I actually saw a highway patrolman on his cell phone the other day!

Yo Revere-

Telephone systems engineer, 25 years' experience speaking here, to tell you exactly why headsets make no difference and cellphone calls impair drivers compared to in-person conversations with passengers. I have also designed a controlled experiment to test my hypothesis, so if you're interested, get in touch via email.

Here's the answer:

The audio signal compression and latency (subtle time lag) on cellphones interfere with the nonverbal content of spoken communications: the cues for emotional state and for passing "permission to speak" between two people. These factors force the user to devote more attention and cognitive capacity to attempting to understand the person with whom they are speaking, than is the case on a corded telephone or an in-person conversation.

The added effort and attention needed to understand cellphone speech are sufficient to cause a decrease in attention to driving or other ongoing tasks (even pedestrians suffer from this when crossing streets while on the cellphone). This produces the classic "driving while celled" effects that resemble DUI.

I know I'm right about this, but would be more than glad to see this tested in a controlled experiment, as follows:

The test condition is cellphone conversation, control 1 is conversation over a landline telephone, and control 2 is conversation in person. (Test and Control 1 can each be done with a standard headset.) The experimental task is to drive a realistic driving simulator. The measure of effect is the number of driving errors recorded on the simulator.

The formal hypothesis is that the error level for cellphone conversation (test condition) will be significantly higher than the error level for Control 1 (landline), and further, that the error level for Control 1 (landlilne) will not be significantly higher than that for Control 2 (in-person).


By the way, there is another effect of the compression & latency (lag) on cellphones: it produces an increase in the level of interpersonal frustration, disagreement, and arguement, compared to a landline phone. This occurs such that for any two comparable conversations, the probability of frustration/arguement increases on a cellphone compared to a landline, as the length of the conversation increases.

That is, if you have a sufficient sample number of conversations of a given length of time on cellphones and on landlines, you will see a significant difference in the level of frustration & arguements: cellphones produce more frustration & arguements than landlines. The persons using the cellphones will also erroneously attribute their frustration to the persons with whom they are speaking, since they are usually unaware of the contribution that the cellphone sound issues are making to the loss of emotional cues and speech hand-off cues.

Here is a specific example. Speech hand-off is normally cued by a pause after speaking. However, with a cellphone, the latency (lag time) is longer and variable compared to a landline or an in-person conversation. Thus for example:

Alice: Hi Bob. (pause for Bob to speak)

Bob: Hi Alice (pause for Alice to speak)

Alice: Hey Bob, I was wondering what your thoughts were about the experiment we're running next week. (pause for Bob to speak)

Now Alice does not hear Bob speak right away following her pause, so she believes that Bob is waiting for her to speak. However, Bob has started speaking, but his speech is delayed due to cellphone latency.

Alice continues, thinking she needs to remind Bob of the project: "You know, the assay-"

Bob has started speaking: "Oh, I was thinking-" and now Bob hears Alice's "reminder," and replies to it, saying, "Yeah I know which experiment-"

Alice meanwhile feels that Bob has interrupted her. She pauses briefly. Her pause causes Bob to stop speaking. For a moment neither of them can figure out who is supposed to speak next....

....etc.... You get the idea. It doesn't take long before one person thinks the other isn't listening to them, which contributes to interpersonal friction...


Yes, I happen to believe that the cellular system as it presently exists, has a uniquely pernicious effect on the quality of interpersonal communication, compared to conventional landlines.

For these reasons I have not had a cellphone in well over five years. The "convenience" factor of pandering to "now-ism" is insignificant compared to the stress factor of dealing with sound quality that is worse than any landline telephone made in the USA since about 1925.

Again for emphasis, I'm a telephone systems engineer, and have been in this field for about a quarter-century.

Anyway, if this stuff interests you, write to me at the address I've left in the address block; or if you can't access it, then post a reply here saying where I can reach you.

BTW, Phila is right on target (I hadn't read all the comments before posting).

Something else:

I've read of a study that found that cellphone use before bedtime causes individuals to take longer to enter the sleep state than does landline use or in-person conversation, and that there is a measurable effect of the cellphone handset's radio freqency emissions on brainwave activity. The industry of course tells us that the latter item is of no importance in the real world.

However, the reports of celled drivers behaving as if in a trance state, and reports such as Floormaster Squeeze's above, of subjective symptoms of trance (s/he didn't remember the road conditions), are convergent with the hypothesis of EEG entrainment by cellphone radio-frequency emissions. Clinical research shows that EEG entrainment, typically through audio signals embedded in music, is a viable method for inducing altererd states (typical applications are in teaching meditation and in stress reduction exercises).

This subject deserves further research. The experiment suggests itself:

Attach a cellphone to a headband worn by a subject on a driving simulator. Test condition: the cellphone is "live" and in conversation mode with no actual conversation occurring. Control condition: the cellphone has its batteries disconnected and is entirely dead. Hypothesis: test will show significantly greater error rate than control, and error rate will increase as a function of the length of time the cellphone is active.

I agree that all cellphone use, handsfree or not, should be illegal while operating a vehicle. Pull over to make the phone call. Cellphones in cars are for emergencies, not for convenience or amusement.

And as for texting, that should obviously be illegal on the road altogether, since it requires taking one's eyes off the road for long enough intervals as to result in a high risk of accidents.

The degree to which individuals are willing to sacrifice "the basics" of life in order to have "bling and frills" never fails to amaze (and disgust) me. For example we demand automobiles with all manner of garbage features, but still don't even have miles-per-gallon meters on the dashboard (except in a few hybrids), which are utterly simple technology. Research shows that when drivers have MPG meters, they change their driving habits to improve fuel efficiency.

Anyway, rant mode off; Revere, feel free to get in touch if this interests you.

Question: Where do cordless telephones used at home fall in the spectrum of user impairment?

By Rene Theberge (not verified) on 05 Dec 2008 #permalink

Hi Rene-

Depends on two things: sound quality, and radio frequency output (RF).

RF output from current generation (last 5 years) household cordless phones is a fraction of that from cellphones, and uses different frequencies that are not associated with potential biological effects. On that count, they're safe.

Sound quality of current-generation cordless phones is also good enough to not pose a problem. I can tell the difference but I have trained ears; but in general the sound quality on a good modern cordless phone (Panasonic or AT&T for example) is excellent.

There are two safety notes about household cordless phones.

One, they get their power from the AC mains, so when you have a power failure, they will cease to function. Power failures are more likely to coincide with other public emergencies such as weather emergencies, earthquakes, and so on. For this reason it's urgently important to have at least one hard-wired telephone that does not require batteries or a wall transformer.

For example Panasonic KX-TS500 or KX-TS550; these can be bought online for about $20 - 25 each and are well worth it (get a few and give 'em out to neighbors:-). Or for example the old fashioned "type 2500 set" that you may recall from when you were a kid, and has the jangly bells. These can be found on Ebay for about $20 "as is" or $50 or more in new condition, or more expensively for older ones in good condition (collectors' items). The 2500 set is designed to last 40 years in constant use.

Two, cordless phones are safe to use in lightning storms under the following conditions: Never use any phone in a lightning storm unless the call is urgent, and keep calls as short as possible; the reason for this has to do with reducing the likelihood of lightning damage to your inside wiring in the building. Never stand close to a window in a lightning storm in case the building or something nearby is hit. (And don't take baths or showers during lightning storms, don't use hand-held appliances plugged into the wall, and all the other usual common-sense measures.)

Since a cordless handset has no wires to the wall, a lightning strike has no way to get to you. In contrast, using a corded phone, lightning can kill you instantly.

So for home use, you should have at least one corded phone for use in power failures, and if you live in an area that gets lightning storms, at least one cordless phone for use during lightning storms.

I remember reading that the phone convo sets up something of a VR in your brain, you are constructing a sort of virtual space that the convo is happening in, since they aren't there with you, and hence a big chunk of attention goes to that. Don't know how much merit it has, but my own experience leans this way too. I think it ties in with some of what has been said about lacking the other cues present in face-to-face communications.