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Cell phones and driving: latest research
Cell phones, driving don't mix
By Mark Floyd
Dec. 9, 2005 -- Most people can rather efficiently walk and chew gum at the same time, but when it comes to more complicated "multi-tasking" - like driving and talking on a cell phone - there is a price to pay.
And no one, it seems, is immune.
"There is a cost for switching from one task to another and that cost can be in response time or in accuracy," said
Mei-Ching Lien, an assistant professor of psychology at Oregon State University. "Even with a seemingly simple task, structural cognitive limitations can prevent you from efficiently switching to a new task."
Psychologists who study multi-tasking have argued for years about whether these "information bottlenecks" occur because people are inherently lazy, or because they have a fundamental inability to switch from one task to another. New studies by Lien and her colleagues at the NASA Ames Research Center in California suggest it is the latter.
Results of their study have been published in the Journal of Experimental Psychology.
In their study the researchers asked volunteers to respond to a variety of auditory and visual cues then measured the responses. When the volunteers prepared for one task, such as responding to the color red, their responses were swift and accurate. When the researchers added a second element - the recognition of shapes as well as color - the task switch considerably delayed the responses, even when the volunteers were prepared for it.
"People are surprised that there is such a delay," Lien said. "Practice can help a person reduce the 'cost' of switching tasks, but it apparently cannot eliminate that cost."
Lien said the study can be applied to the real world, especially to drivers who talk on cell phones. On the surface, she said, it appears that drivers are trying to accomplish just two tasks - driving and conversing. But each task is complicated and multi-faceted, greatly increasing the "cost" of switching. The result: inattention and slow reaction times.
"A lot of people think talking on the cell phone while driving is natural, but each time someone asks a question or changes the subject, it's like taking on a new task," Lien said. "It requires a certain amount of thought and preparation. It's actually quite different than listening to the radio, where you don't need to respond.
"And it's also different from talking to a passenger in the vehicle," she added. "In most cases, a passenger can observe when there is a dangerous traffic situation and keep quiet. But someone calling you on a cell phone won't have a clue."
There are individual differences in the costs of multi-tasking, Lien said. In her lab studies, a typical response to a single stimulus might take 300 milliseconds. Adding a second task increases the response to about 800 milliseconds. A millisecond is 1/1000th of a second, so the delay may not seem like much - until you extend the difference to a car driving 60 miles an hour and realize the response rate more than doubles, Lien said.
In her lab studies, she has yet to test any volunteers who are immune to delays in multi-tasking, though she says some students do much better than others.
"I have to say that the best ones are those who play a lot of video games," she pointed out. "Those are lab studies, however, and not driving tests."
She became interested in multi-tasking while working at the NASA Ames Research Center in Moffett, Calif., where she was part of a team analyzing cockpit design and pilot function. One of the projects focused on how much information can safely and efficiently be included on screens and monitors so the pilots' delay and loss of accuracy are minimized.
"We learned to modify some of the screens to mitigate their weaknesses," she said.
While Lien's studies suggest that simplifying tasks leads to greater efficiency, technology is complicating everything we do - including driving. Drivers often use cell phones, CD players, global positioning systems, radar detectors, complicated dashboards and other devices. At the same time, they must navigate increasing traffic, read a plethora of signs, and handle other distractions.
"We may be undermining our ability to drive safely," Lien said.
New study shows drivers using cell phones twice as likely to cause rear-end collisions
Drivers talking on cell phones are nearly twice as likely as other drivers involved in crashes to have rear-end collisions, according to a new University of North Carolina at Chapel Hill study. Crashes involving cell phone use, however, are less likely to result in fatalities or serious injuries than crashes not involving the devices.
Almost 60 percent of licensed N.C. drivers have used a cell phone while behind the wheel, investigators from the UNC Highway Safety Research Center (HSRC) found. The most common violations for drivers involved in collisions while talking on phones were failure to reduce speed, traffic signal violations such as running red lights, speeding, following too closely and failing to yield to other vehicles.
"Not surprisingly, cell phone users were less likely than those who don't have them to perceive talking while driving as a distraction or safety concern," said Dr. Jane Stutts, associate director for social and behavioral research at HSRC. "They were also less supportive of legislation that would ban drivers' use of cell phones or issue stricter penalties for cell phone users involved in crashes. However, three-fourths of both groups indicated they would support legislation prohibiting the use of hand-held phone by drivers, except for emergencies."
Stutts' study, "Cell Phone Use in NC: 2002 Update Report," was sponsored by the NC Governor's Highway Safety Program and is an extension of earlier work issued in November 2001.
Co-authors of the new report released today (March 26) are Dr. Herman Huang and William W. Hunter, research associate and associate director, respectively, at HSRC. Senior computer analyst Eric Rodgman helped with data gathering and analysis.
The investigation involved a statewide telephone survey of 500 cell phone users and 150 others to gauge driving-related behavior and opinions.
Also included were analyses of characteristics of cell phone-related crashes based on 452 such incidents found during a computerized search of N.C. crash report narratives from 1996 through August 2000. In addition, the N.C. State Highway Patrol collected more data for the study over two months last summer.
"We wanted to know how many people were talking on cell phones while driving and how many crashes were cell-phone related," Stutts said. "We also wanted to find out more about these crashes."
Based on the data collected, the researchers estimate that cell phones are responsible for at least 1,500 motor vehicle crashes across the state each year.
Other findings were that:
* Drivers most often talking on cell phones were between ages 25 and 39, and a higher proportion of users drove sport utility vehicles than non-users.
* The average time per day spent talking on phones while driving was 14.5 minutes, while the medium time was five minutes. Talk time decreased with increasing age and was higher among males than females.
* One in four users had a hands-free device although they did not always use it when talking.
* Cell phone crashes were more likely to occur during mid-day and afternoon hours in urban areas and on local streets.
* Most cell phone users were at least partially responsible for their crashes.
Investigators identified cell phone-related crashes by running computerized searches for collision reports in which officers specifically mentioned the telephones in their descriptions each crash, Stutts said.
The special two-month data collection effort by the N.C. Highway Patrol found that of the 29 identified cases, all but one involved a hand-held phone.
Most occurred while drivers were talking on their phones but some involved reaching for, dialing, getting ready to dial, answering or picking up dropped phones or hanging up.
Based on reported cases, the team estimated that cell phones were involved in at least 0.16 percent of crashes in non-metropolitan areas or about one in 623 reported crashes, she said. The 29 reported cell phone collisions projects to 174 cases annually.
Nine out of 10 crashes, however, occurred within municipal areas.
"In fact, only an estimated 11.8 percent of the crashes identified from the 1996-2000 narrative search were reported by the Highway Patrol," Stutts said. "Although this number represents only a small percentage of all reported crashes in the state, 1,500 crashes is still too many, especially for something that could easily be avoided. Drivers need to remember that their first responsibility is to pay attention to their driving."
Cell phone users drive like old folks
If you have been stuck in traffic behind a motorist yakking on a cellular phone, a new University of Utah study will sound familiar: When young motorists talk on cell phones, they drive like elderly people, moving and reacting more slowly and increasing their risk of accidents.
"If you put a 20-year-old driver behind the wheel with a cell phone, their reaction times are the same as a 70-year-old driver who is not using a cell phone. It's like instantly aging a large number of drivers," says David Strayer, a University of Utah psychology professor and principal author of the study.
Frank Drews, as assistant professor of psychology and study co-author, adds: "If you want to act old really fast, then talk on a cell phone while driving."
The new study by Strayer and Drews was published in this winter's issue of Human Factors, the quarterly journal of the Human Factors and Ergonomics Society.
The study found that when 18- to 25-year-olds were placed in a driving simulator and talked on a cellular phone, they reacted to brake lights from a car in front of them as slowly as 65- to 74-year-olds who were not using a cell phone.
The elderly drivers, meanwhile, became even slower to react to brake lights when they spoke on a cell phone. But the good news for elderly drivers was that their driving skills did not become as bad as had been predicted by earlier research showing that older people performing multiple tasks suffer additional impairment due to aging.
The study found that drivers who talked on cell phones - regardless of whether they were young or old - were 18 percent slower in hitting their brakes than drivers who didn't use cell phones. The drivers chatting on cell phones also had a 12 percent greater following distance - an effort to compensate for paying less attention to road conditions - and took 17 percent longer to regain the speed they lost when they braked.
In addition, "there was also a twofold increase in the number of [simulated] rear-end collisions when drivers were conversing on cell phones," the study says.
Driving to distraction: How the new study was performed
Strayer and his colleagues are widely known for their 2001 study showing that hands-free cell phones are just as distracting as hand-held cell phones, and for a 2003 study showing that the reason is "inattention blindness," in which motorists can look directly at road conditions but not really see them because they are distracted by a cell phone conversation. The research has called into question legislative efforts by various states to ban motorists from using handheld but not hands-free cell phones.
The same researchers also gained publicity for another study, which was presented at a scientific meeting in 2003, showing that motorists who talk on cell phones are more impaired than drunken drivers with blood alcohol levels exceeding 0.08.
The new study included 20 older adults (ages 65 to 74, with average age 70) and 20 younger adults (ages 18 to 25, with average age 20). All of them had normal vision and a valid driver's license. Preliminary tests showed older people were slower to process information, as was expected.
Then the psychologists had the young and older study participants "drive" in a high-tech driving simulator. Participants in the simulator used dashboard instruments, steering wheel and brake and gas pedals from a Ford Crown Victoria sedan, surrounded by three screens showing freeway scenes and traffic, including a "pace car" that intermittently hit its brakes 32 times as it appeared to drive in front of study participants. If a participant failed to hit their own brakes, they eventually would rear-end the pace car.
Each participant drove four simulated 10-mile freeway trips lasting about 10 minutes each, talking on a cell phone with a research assistant during half the trips and driving without talking the other half. Only hands-free phones were used to eliminate any possible distraction from manipulating a hand-held cell phone.
Thirty times each second, the simulator measured the participants' driving speed, following distance and - if applicable - how long it took them to hit the brakes and how long it took them to regain speed. Those factors "have been shown to affect the likelihood and severity of rear-end collisions," Strayer and Drews wrote.
The findings: Age and cell phone use impair drivers
The study found that:
-- Compared with young drivers, older drivers were slower to hit the brakes when needed, tended to hit the brakes twice, took longer to regain speed and had a greater following distance. This was true when young and old participants drove with or without cell phones.
-- Compared with drivers who did not talk on cell phones, those who used a cell phone while driving were slower to hit the brakes, had a longer following distance and took longer to regain speed . This was true of both young and old drivers. "Once drivers on cell phones hit the brakes, it takes them longer to get back into the normal flow of traffic," Strayer says. "The net result is they are impeding the overall flow of traffic."
-- When young drivers used cell phones, the reaction time in hitting the brakes slowed to match that of elderly drivers who did not talk on cell phones, namely, an average of 912 milliseconds, or a bit more than nine-tenths of a second. When not talking on cell phones, young motorists hit the brakes within an average of 780 milliseconds, or almost eight-tenths of a second. The difference may seem small, but represents a 17 percent slower reaction time. Strayer says other studies have shown that much of a decrease in reaction time increases both the likelihood and severity of accidents.
-- When elderly drivers used cell phones, their reaction times got worse, but not as bad as had been expected. Previous research "suggested older people should have been really messed up if you put them on a cell phone because, not only are they slower overall due to age, but there's a difficulty dividing attention that should make using a cell phone much more difficult for them than for young people," Strayer said. Yet the study "suggests older adults do not suffer a significantly greater penalty for talking on a cell phone while driving than do their younger counterparts," Strayer and Drews wrote.
That may be because older adults have more experience driving and take fewer risks, and those in the study may have been healthier than other seniors, Strayer says.
Crashing while talking
Federal statistics show that the most accident-prone drivers are the young and old, with fatal accident rates high during teenage years, then declining until age 30 and staying relatively level until age 60, when accident rates climb again as age increases.
Six participants in the new study rear-ended the pace car while driving the simulator. Four accidents (one older adult and three younger adults) happened while the participants talked on cell phones. Two did not (one older adult and one younger adult).
There were too few collisions for statistical analysis. But Strayer notes that twice as many accidents happened to motorists on cell phones compared with motorists who were not talking. And young drivers were in collisions twice as often as elderly drivers.
"Older drivers were slightly less likely to get into accidents than younger drivers," Strayer says. "Why? They tend to have a greater following distance. Their reactions are impaired, but they are driving so cautiously they were less likely to smash into somebody," although in real life, "older drivers are significantly more likely to be rear-ended" because of their slow speed.
When Strayer and Drews combined the new accident data with simulated driving accidents in their earlier studies, they counted 12 rear-end collisions among 121 study participants. Ten of the collisions happened when motorists were talking on cell phones.
That is statistically significant and provides "clear evidence that drivers using a cell phone were more likely to be involved in a collision than when these same drivers were not using a cell phone," the psychologists wrote.