We've reported on studies about cell phones and driving before. A general consensus has formed that driving with cell phones (even hands-free phones) is dangerous. What matters most, it appears, isn't so much the physical aspect -- holding and operating the phone -- but how demanding the conversation itself is.
Research on aging has suggested that older drivers may be even more impaired by driving with a cell phone than younger drivers, since older adults tend to perform worse on "dual task" activities than younger adults. But what about the years of driving experience that older adults have? Can't they compensate for slower reaction time with more careful driving?
David Strayer and Frank Drews had older and younger adults perform the same driving simulator task. Half of them talked on a hands-free cell phone while driving, and the other half didn't. The task was to follow a pace car in the right lane of a three-lane freeway. The pace car was programmed to randomly brake at random intervals along the 24-mile simulated course. Here's a picture of the simulator they used (from the manufacturer's web site):
Are you having a flashback to driver's ed class yet? The simulator is actually the type used for police training, with feedback on the steering wheel and pedals for a relatively realistic driving experience -- probably a bit more high-end than the typical high school setup (my high school had a big room with a movie projector in the back, and plastic box with a toy steering wheel on each student's desk). Strayer and Drews charted the braking action of each group of participants starting at the point the pace car's brake lights came on. Here are the results:
As you can see, older adults display a different pattern of braking than younger adults, with two distinct humps in their braking curve, one about a second after the pilot car braked, and a second one about two and a half seconds later. But both younger adults and older adults showed a decrease in performance when talking on the cell phone (dual task). The best way to see the difference is to compare the back side of the curves for each group -- for the dual task groups, the brakes came on later and were released later, whether the drivers were old or young. Older drivers performed worse than younger drivers, but the difference between single- and dual-task conditions was the same for both groups.
Of greater significance were the six collisions that occured during the study. Two were during the single-task condition, and four were in the dual-task condition. While this difference wasn't significant, when combined with the results of two similar studies performed by the same research group, with a total of 121 participants, there were two crashes in the single-task condition and ten in the dual-task condition -- a significant difference in collisions while driving with a cell phone.
Older drivers were actually involved in fewer collisions than younger drivers, which Strayer and Drews attribute to the fact that older adults drove significantly slower than younger adults throughout the experiment (an average of 53.7 mph compared to 62.1 mph in the dual-task condition).
Strayer and Drews do point out that all the older drivers in their study, though they averaged 69.6 years of age, were quite healthy and vigorous. Since they were recruited via newspaper ads, they may have been healthier than average people the same age, and this may account for the lack of an effect of age of drivers.
I'd add an additional concern: the study included only 6 older women (compared to 14 older men), and we have reported here on a study showing that older women are less able to compensate for driving with cell phones than other individuals. It's possible that if more older women were included in the study, the results would have been different.
Strayer, D.L, & Drews, F.A. (2004). Profiles in driver distraction: Effects of cell phone conversations on younger and older drivers. Human Factors, 46(4), 640-649.
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On driving with cell phones- There was a great study we learned about in intro to cog sci: Subjects were asked to observe a screen of (I think) black and white objects moving around and count every time a black one hit a boundary. Half of the participants were talking on a cell phone and half weren't. They did equally well on counting, but of course there's a fun part: In the middle of the animation, a funky green shape moved across the screen. Subjects were asked if they noticed anything odd during the trial. The non-cell phone talkers noticed the green shape at a rate something like ten times that of the cell phone talkers. That sounds like it relates to the real danger of driving while talking: all of your unconscious, secondary attention goes away.
Trying to use a cell phone while driving sure impairs me, so I avoid it unless there's very little traffic and I have lots of room around me. Maybe it's because I rarely use the phone anyway, so manipulating it has not become reflexive (or compulsive, for that matter).
Another thing the authors point out is that talking on a cell phone makes a 20-year-old's reaction time about equal to a 65-year-old. Quite something, really!
Maybe the older people have that double-braking pattern because they've become accustomed to pumping their brakes since they learned to do so when they learned how to drive. Now that cars come standard with ABS, pumping the brakes are no longer necessary so younger people aren't likely to doing so.
Anyway, just a theory...
(1)Has anyone compared the reaction times to people talking to someone in (say) the back seat of their own car?
(2) If they do, should we make it illegal to talk while driving?
David,
I see your point, and yes, some research has been done in that area (one such study is linked above, but here's the link again). Indeed, conversations within a car are just as bad.
I don't think we should outlaw in-car conversation, and I don't think we should outlaw cell phones, but I do think the more we know about the dangers of cell phone use and the situations where they are more dangerous, the better off we are.
One important point the authors of this study make is that all drivers tend to increase following distance while on the phone, and that's at least partially a good thing. The downside is, when following distances get too large, the chances that someone will merge in front of you and potentially not be noticed also increase.
Sorry I missed that link! I was (I hope) kidding about illegal. However, I wonder if it is the talking that is the problem. It occurs to me that we use visual cues in conversation and, perhaps, in a phone conversation you mentally picture the person's reactions and expressions close to, creating a conflict with the mid distance visual cues you need to react to. Strictly functional talk may not be distracting (eg between pilot and ground), as it is intended by the participants to be used in that environment and so is used with the minimum of expression.
I think that Andy Affleck makes a similar point in his comment on the conversation study.