Rapid Responses to:
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Rapid Responses: Rapid Responses published:
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![[Read Rapid Response]](/icons/misc/sectionDOWN.gif)
Scrutiny of Cell Phone Statistics
- A. Elizabeth Griffith (13 July 2005)
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Ban Conversation
- Alexander C. Tsai (14 July 2005)
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Talking and driving
- Sam Richmond (14 July 2005)
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Re: Scrutiny of Cell Phone Statistics
- Andrew Thatcher (15 July 2005)
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Causality
- Ben Palmer (16 July 2005)
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Limiting selection of participants to those involved in an accident skews results.
- Mitchell L Frieder (16 July 2005)
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Attitudes to transport casualties: private versus public
- Tony H. Reinhardt-Rutland (29 July 2005)
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Re: Attitudes to transport casualties: private versus public
- Ben Palmer (3 August 2005)
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Conversation with passengers likely to be safer than via the phone
- Matthew L Grove (4 August 2005)
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Re: Conversation with passengers likely to be safer than via the phone
- Ben Palmer (4 August 2005)
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Reply to Ben Palmer
- Matthew L Grove (5 August 2005)
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RF from a cell phone may be a factor
- John M. Williams (20 August 2005)
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Driving time is not "downtime"
- Richard K Howell (22 August 2005)
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Methodologic Limitations of the Case-Crossover Study
- David A Lombardi (25 August 2005)
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Re: Multi-tasking
- John H. Lange (28 August 2005)
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Re: RF from a cell phone may be a factor
- Ben Palmer (29 August 2005)
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Re: Re: RF from a cell phone may be a factor
- John M. Williams (30 August 2005)
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Mobile phones, alcohol or high speeds?
- Frank J Leavitt (31 August 2005)
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Driven To Distraction
- LAYAN B GAMAGE, Sohail Akhtar, Steven S Southern. (10 September 2005)
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Authors' reply
- Suzanne P McEvoy, Stevenson MR, McCartt AT, Woodward M (15 September 2005)
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mobile phone health issues
- Anthony G Harrison (7 November 2005)
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cell phone usage while driving
- Jeremy C. Klein (1 February 2006)
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A balanced view of driver distractions
- David Clegg (20 February 2007)
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Study Bias
- Ian Thomason (2 April 2008)
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A. Elizabeth Griffith, Senior Analysis Engineer Orbital Sciences Corp, 3380 S. Price Rd., Chandler, AZ 85248
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The conclusion that cell phone users are four times as likely to crash and go to hospital was not actually borne out by the data presented by McEvoy et al on July 12, 2005. Astute readers can see that only 2% of the crashed drivers (40 out of 1625) used a cell phone for up to 10 minutes before their collisions. Further, common sense dictates that once you hang up from a call, and minutes tick by, your attention for driving increases back to normal. Therefore, less than 2% of the crashed drivers were actually on the phone (or influenced by the phone) during the collision. Is it worth world-wide headlines (not to mention road-rage against cell phone users) to get worked up over a trend that was shown by less than 2% of the drivers? Surely more than 0.5% of drivers are using cell phones at any given time, so that if they were four times as likely to be in a collision, we would see more than 2% of the hospitalizations to occur due to cell phone use. I would urge fellow scientists to keep a watchful eye in the face of elaborate statistical methods. Competing interests: None declared |
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Alexander C. Tsai, Medical Student Case Western Reserve University School of Medicine, Cleveland, Ohio, USA 44106-2459
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Editor -- In the recent case-crossover study by McEvoy et al. on the use of mobile phones and their role in motor vehicle crashes, the authors found that mobile phone use was associated with an increased likelihood of crashing. The odds ratios for hand-held vs. hands-free mobile phone use were similar.
It could be that the risk factor for crashing is conversation itself, not necessarily mobile phone use. The most direct way to assess this would be to compare not only mobile phone use during crash trips vs. control periods -- but also conversation (with or without mobile phone use, perhaps making the reasonable assumption that conversation is occurring with mobile phone use) during crash trips vs. control periods. If conversation is the true risk factor, then the odds ratios for mobile phone use (hand-held or hands-free) and conversation would be similar and elevated compared to non-use and silence. McEvoy et al. do not report this data, however, but one easily accessible proxy for conversation would be the presence of additional occupants in the motor vehicle. Did McEvoy et al. stratify their results by number of additional occupants in the motor vehicle? This raises an additional policy question: If further study finds that conversation is a risk factor for motor vehicle crash and that conversation generates the same elevated risk for crash as mobile phone use, what are the policy implications? To ban conversation while driving? Competing interests: None declared |
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Sam Richmond, Consultant Neonatologist Sunderland, SR4 7TP
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I seem to remember that all London Transport buses, and probably many others, have a sign asking passengers not to talk to the driver while the vehicle is in motion. Competing interests: None declared |
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Andrew Thatcher, Senior Lecturer University of the Witwatersrand
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I am afraid the author's are correct (40 out of 456 or 9%). While 1625 drivers were initially approached, all but 456 volunteered to participate (including making cell phone records available for scrutiny). There results say nothing about the people who chose not to participate or were excluded for a variety of reasons (not-related to the outcome of the study). The author's are also correct in assuming that this is a conservative statistic (the volunteers may very well have withdrawn for social desireability or legal reasons related to their cellphone use, we just don't know). It is conservative for other reasons too. For example, their study only looked at people who sought hospitalisation (what about the other people who just had a little bumper-bashing, or bumped the curb? what about people who died as a result of a collision or accident? and what about the many near-misses because of the vigilance of other driver's on the roads?. To me 9% is frighteningly high in this type of self- admitting research. Competing interests: None declared |
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Ben Palmer, Engineering 1200 Geneva
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In over 85% of the cases, multiple vehicles where involved. Did the study take into consideration the causality of the use of the phone? Was the driver initially causing the accident using the phone at the time of crash? How can an accident be attributed to the use of a mobile phone if it is caused by a driver not included in the study? This study is singling out one possible (?) cause for accidents, and comes to the conclusion that the use of mobile phones should be prohibited in moving vehicles. Didn't accidents happen before the invention of mobile communication? What would/could the driver have done had he/she not used the phone at the time of the crash? Talk to a passenger, listen to the radio, change a CD, think about a job related problem, sing a song, look in the rear mirror while the car in front slams the brakes, ... there is no guarantee that the driver wouldn't have been occupied by any of these other distracting activities. There is no mention of these potential confounders in the study. Competing interests: None declared |
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Mitchell L Frieder, Educator Art Institute of California 90405
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In reponse to the article: "Role of mobile phones in motor vehicle crashes resulting in hospital attendance: a case-crossover study" by Suzanne P McEvoy, et al. BMJ, Jul 2005; 10.1136/bmj.38537.397512.55. The selection of participants only from a pool of drivers who had been involved in automobile accidents skews the results of the study. It is quite possible that there exists a large number of cellphone-using drivers who are able to properly control their vehicles while using phones and therefore never be involved in an accident. In order to correctly conduct a study of this subject, one must draw participants from the population of all cellphone owners who drive while using their phones, not just from those who have been in accidents. Competing interests: None declared |
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Tony H. Reinhardt-Rutland, Reader School of Psychology, University of Ulster, BT37 0QB
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McEvoy et al show that use of a cell phone - whether hand-held or not - increases the chances of the driver crashing. This seems perfectly plausible: distraction from performing the complex task of driving must be a likely prelude to a crash. What is interesting is the somewhat negative responses from some of the commentators. One may want to dispute the size of the effect (eg Griffith), but if the research had referred to other modes of transport - Richmond refers to London Transport buses - the attitudes might be entirely different. To take an issue that has affected the British rail network: at immense cost, legislation has virtually eliminated slam-door rolling-stock - but the saving in casualties will be puny. We expect a disproportionate amount of effort in saving casualties in public transportion, but any minimal curtailment of the private motorist's "freedom" is too often accompanied by a vociferous backlash. Competing interests: None declared |
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Ben Palmer, Engineering Geneva
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As Reinhardt-Rutland points out: "distraction from performing the complex task of driving must be a likely prelude to a crash". Singling out a trendy object such as the mobile phone, makes this study more attractive, but doesn't really address the problem. Any activity besides driving, and even activities directly related to driving, may distract the driver from an upcoming situation that requires special attention. The problem is not the mobile phone in particular. Conversation with a passenger, having kids in the car, operating the radio, checking the speedometer, looking in the rear mirror, are all potential sources of distraction. Some of them may be avoidable, some not. As long as humans drive cars, human errors will not be avoidable, even with the most restrictive legislation. Don't even try it ... Competing interests: None declared |
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Matthew L Grove, Consultant Rheumatologist NTGH, NE29 8NH
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Thank you to McEvoy and colleagues for a detailed and thorough attempt at a tricky research subject. The critical commentators on the paper don't seem to fully understand the research methodology - the results show that 9% of the 456 subjects available for analysis were on the phone shortly before the time of their crash, according to phone company records. They were four times more likely to be on the phone shortly before their accident than at a similar time of day when they were also driving their car but did not crash. This finding was tested robustly using different control periods with the same result. All the various biases introduced by the interview-style study design are likely to make this a conservative risk estimate. The true risk is probably greater, but harder to measure where subjects can refuse to participate. I'm not at all surprised that hands-free units were no less risky than hand-helds. I agree with various of the other respondents that the distracting effects of conversation is probably at fault. However I don't think passengers (at least adult passengers) are a good control group. A passenger (particularly in the front seat) is aware of the road conditions, and, if a driver themselves, will vary their conversation to match the conditions and allow the driver to concentrate. Someone on the phone has no idea of traffic conditions, and in this is similar to a petulant child in the back seat who keeps talking and asking questions no matter what is transpiring in the immediate vicinity outside the car. Whether hands-free or voice activated, such a conversation will be a distraction that will increase the risk of a crash if road conditions become more dangerous. Competing interests: Have a mobile phone in my car, but always pull over to use it. |
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Ben Palmer, Engineering Geneva
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Grove disputes the fact that a passenger could be as much of a distraction as using a cell phone. He is proven wrong by another study based on accident data, conducted by the University of North Carolina Highway Safety Research Center. http://www.hsrc.unc.edu/pressrelease/distraction_testimony.htm This study clearly shows that the highest distraction comes from an outside person, object or event (out of control of the driver!) 29.4%, followed by adjusting radio (11.4%), other occupant in the vehicle (10,9%), [...], adjusting vehicle/climate controls (2.8%), eating/drinking (1.7%), using/dialling cell phone (1.5%), [...]. Other distractions account for 25.6%. Having a cell phone in a car, even if not used while driving, is nevertheless a potential source of distraction, unless it is switched off. An incoming call while driving forces the driver to rapidely take the decision whether to answer the call or not, hence focusses all the attention. Pulling over (in a hurry) is a hazardous manoeuvre, also for the surounding traffic. Competing interests: None declared |
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Matthew L Grove, Consultant Rheumatologist NTGH, NE29 8NH
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Thanks to Ben for setting me right and pointing me towards the North Carolina study. However the figures he quotes simply refer to the proportion of drivers distracted by a particular form of hazard. Ie whilst 10.9% of drivers were distracted by another vehicle occupant, only 1.5% admitted to using a cell phone at the time of the crash. This amounts to asking how often a particular distraction was present, rather than how distracting it was to the driver. In the words of Jane Stutts, the author of the study herself: "Our analysis was not intended to provide definitive answers as to which distractions pose the greatest risk to drivers. Additional data are needed to address this question, including information on how often and under what conditions drivers engage in different distracting behaviors." Which is exactly what McEvoy and colleagues have tried to do. Furthermore, Jane Stutts clearly suspects the 1.5% cell phone figure may be an underestimate: "People may believe that admitting to cell phone use at the time of their crash puts them in more legal or financial (insurance) jeopardy than admitting to spilling a cup of coffee or dropping a CD." For the record, my mobile phone is usually switched off. I use it to respond to my aircall pager - once I've found a safe place to pull over, of course! Competing interests: None declared |
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John M. Williams, Business owner Markanix Co., P. O. Box 2697, Redwood City, CA, 94064
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It can be shown rigorously that microwave radio-frequency (RF) from a cell phone causes hyperpolarization of cell membranes independent of any measurable thermal effect. The effect on active neural or muscle membranes is greater than on resting membranes. I can supply a copy of a paper to interested readers giving the calculations proving this. Now, when a cell phone is transmitting, there are two possible different paths for RF from the device to the user's head: First, there is the path through air. About 40% of the device output power will be incident on the head if the device is held against the head. When hands-free mike and earphones are in use, the power on this path is reduced to very low levels because of the inverse-square law governing intensity as a function of distance from the transmitter. Secondly, any hands-free wiring is conductive metal and is terminated in the eletronics of the transmitting device. Therefore, there is a second nonradiative path for RF electrical transmission along the hands- free wiring directly to the head. I can not quantify this possible path (the problem is very difficult and poorly constrained), but it surely exists. Further study of this possibility should be done and reported to health authorities. So, it would seem that RF input to the head might not differ much whether the device was operated hands-free or on the side of the head. Obviously, a wireless hands-free appliance would itself produce RF on or near the head. Membrane hyperpolarization can cause loss of smooth-muscle tonus and thus possibly lowered blood pressure or headache. On skeletal muscle, it could cause weakness or miscoordination. It could interfere with the primarily inhibitive action of the neural circuitry of most of the brain. Therefore, perhaps the reported lack of influence of the hands-free appliances on accident rate might be explained because elevation of the accident rate primarily was because of RF and not inattention to the road? On a related issue, I also should point out that regardless of the cause of these accidents, having two hands on the wheel should improve chances of recovery from danger; therefore, there would seem to be something wrong with studies not showing an effect of the hands-free appliances. Perhaps, persons using a cell phone while driving would not be competent enough drivers to recover from a dangerous situation any way? Competing interests: The author owns shares in companies manufacturing cell phones. |
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Richard K Howell, Director of driver safety and wellbeing Macclesfield UK SK10 4TF
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Whilst agreeing with the other respondents that passengers can be distracting (we have a 3-year old) a key issue is the use of cell phones during work time, presumably when the 3 year-old is not in the vehicle! Work-related driving accidents are a significant percentage of all accidents in companies with commercial drivers - a third of our accidents are vehicle-related. Cell phone use is an avoidable risk when driving - the perception is that it is an acceptable activity to increase business during the "downtime" of driving. This is a frightening increase in risk to employees during an 8 hour day. Legislation is unlikely to affect this perception greatly; only when all levels of management visibly demonstrate that cellphone use whilst driving is unacceptable will this change. This study is an excellent tool to help safety professionals to begin this transformation of perceptions. Competing interests: Project director for global driver safety at a large pharmaceutical company |
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David A Lombardi, Injury Epidemiologist Liberty Mutual Research Institute for Safety
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I read with interest the case-crossover study published by McEvoy, Stevenson, et al. (BMJ 2005; 331:428) that reported that use of a mobile phone up to 10 minutes before a crash by a driver was associated with a fourfold increased likelihood of crashing. The authors were innovative in choosing the case-crossover design to control for many of the important and challenging between-subject confounders (age, visual acuity, etc) to evaluate the role of mobile phones in vehicle crashes. However, we previously published a number of methodological caveats when using this relatively new study design that may impact the validity of their findings (Sorock, Lombardi, et al, 2001). Primarily, the reasonable possibility of uncontrolled within-subject confounding in their study. This confouding is possible for multiple, correlated, transient factors which change over time within a subject. One example in this study would be the use of a mobile phone (ie, distraction) which either speeding or moving thru hazardous roads. Thus, within-subject confounding would uncontrolled for and a potential threat to the internal validity of their findings. Sorock GS, Lombardi DA, Gabel C, Smith GS, Mittleman MA. Case- crossover studies of occupational trauma: Methodological caveats. Inj Prevention 2001; 7 (suppl I):38-42. Competing interests: None declared |
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John H. Lange, Environmetnal and Occupational Health Consutlant Envirosafe Training and Consutants, P.O. Box 114022, Pittsburgh, PA 15239 (USA)
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What McEvoy et al., in their paper of July 12, 2005 (BMJ 2005; 331:428), should really emphasize is that multi-tasking is not an appropriate or applicable function for people, especially when risk is involved. It is not difficult to realize that attempting to concentration on two or more subjects simultaneously is not possible. When this does occur one of the activities will suffer, as noted, although with methodological problems associated, in the study by McEvoy et al. It is likely that if a similar study were conducted involving other activities that are distracting and/or require multi-tasking (Grove, B. August 4, 2005, BMJ, Rapid Response, Conversation with patients likely to be safer than via cell phone, in response to McEvoy et al.) results will be similar to that observed in the McEvoy et al., investigation. So, let’s not blame cell phones for our brains inability to serve multiple functions. Competing interests: None declared |
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Ben Palmer, Engineering Geneva
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John M. Williams wrote: " So, it would seem that RF input to the head might not differ much whether the device was operated hands-free or on the side of the head. Obviously, a wireless hands-free appliance would itself produce RF on or near the head." In fact, RF is present as long as the phone is switched on, whether a conversion takes place or not. If simply the presence of RF was the cause, then the study would not have shown an association between mobile phone conversation, because presumably the phone was also present in the control situations. Competing interests: None declared |
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John M. Williams, Business owner Markanix Co., P. O. Box 2697, Redwood City, CA 94064
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Yes, RF is present. The problem is that I don't have the information to estimate the RF dose from a WIRED hands-free appliance. The way cell phones work, is that they greatly increase their transmitting power while the user speaks. I can detect nearby conversation using a pocket microwave detector, but only when the user is speaking, not while he or she is listening. Therefore, time-averaged RF dose definitely increases during conversations. My point of puzzlement is that the degradation of driving performance occurs, apparently, when a hands-free appliance is in use. This MIGHT be because of RF conducted along the wires to the head. I mentioned this because, if so, RF power to the head might well be the same whether a hands-free WIRED appliance was in use or not. Of course, a wireLESS hands-free appliance also would transmit during conversation. But, I think, it would not transmit at all otherwise, because such appliances would have no cause to try to maintain contact with the best of several distant cell towers. I wonder if anyone has a handed vs. hands-free accident database in which hands-free WIRED vs WIRELESS appliances are distinguished? Competing interests: The author owns shares in companies manufacturing cell phones. |
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Frank J Leavitt, Chairman, Centre for Asian and International Bioethics Faculty of Health Sciences, Ben Gurion University of the Negev, Beer Sheva, Israel. 84105
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With all due respect to the authors, it may not have been necessary to do such an elaborate study for something so obvious. Just watch all those cars wandering drunkenly around. Every time I catch up with one and have a look, the driver has a mobile phone in his hand, and not a bottle of whisky. I would be interested in seeing some epidemiology on which is the greater road hazard: mobile phones, alcohol or high speeds? Of course maybe with time people will get used to talking on phones while driving and learn how to do it more safely. But we'll have to go through plenty of accidents before we get to that. Competing interests: None declared |
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LAYAN B GAMAGE, SHO In Plastic Surgery Pinderfields General Hospital, Wakefield, Yorkshire WF1 4DG, Sohail Akhtar, Steven S Southern.
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Driven To Distraction Dear Sir, I read with interest the article by Mcevoy et. al. in the August issue of the BMJ, regarding the danger of using mobile phones with or without hands free kits(1). The conclusion of a fourfold increase in the likelihood of crashing with mobile phone use is a rather worrying thought. Although most of us are now aware of the dangers of driving whilst using a mobile phone, we assume that a hands-free kit would have significantly decreased this risk. This leads to the obvious question as to why the risk is not reduced. The work has stimulated us to perform a literature search to assess whether other distracting factors whilst driving have been cited as having an impact on traffic related injuries and also contemplate other factors that may result in adverse events during driving. Not paying attention to the immediate environment is one of the main factors in traffic accidents (2). In addition to performing physical tasks requiring the simultaneous coordination of all 4 limbs in different directions with differing force, driving also requires mental alertness. In order to drive safely we are advised to be aware of the environment all around us through the constant use of our windows and driving mirrors. Anything which distracts our attention is surely compromising our alertness. Distractions may be both exogenous –from external objects- and endogenous –from the driver’s thoughts, or cognitive activity(3). While exogenous distractions may obviously provide visual compromise, endogenous distractions have also been shown to impair visual processing(4). The rapid advances of mobile phone technology have been mirrored by the technologically evolving cockpit of the average family car. As such, exogenous distractions are often built into modern cars. Satellite navigation systems, DVD players, audio players, GPS systems, and displays which control the car’s internal environment are all fairly common. Compare the dashboard of a modern executive saloon with a car from 50 years ago, and the need for extra attention becomes obvious. Certain manufacturers have attempted to simply dashboard aesthetics by adopting the concept of one button to control all functions. These devices usually require the operator to scroll through menus and options on centrally mounted computer screens. There are plenty of other exogenous distractions in addition to the car itself. Passengers of whatever age will seldom travel in complete silence. The risks of fatal injury in 16 – 17 year olds have previously been related to the number of occupants in the vehicle (5). The explanation given is that the presence of passengers increased risk behaviour in the younger driver group. We have long since known the dangers of driving under the influence of alcohol and drugs. What of the influence of tobacco in the car? Smoking requires the use of a limb, and distracts the driver. Similarly, eating and drinking require a degree of attention. Despite this, ash trays and cup holders are still ever more common in cars. We feel this discussion may add some more depth and insight into the hazards and potential injury related to distracting factors encountered by the average driver and limiting mobile phone use whilst driving may only be addressing one in a number of factors which will result in a safer driver. 1 McEvoy P, Stevenson M, McCartt A, Woodward M, Haworth C, Palamara P, Cercarelli R. Role of mobile phones in motor vehicle crashes resulting in hospital attendance: a case-crossover study. BMJ. 2005;331:413-464. 2 Rumar K. The basic driver error:late detection. Ergonomics. 1990;33:1281-1290 3 Recarte M, Nunes L. Mental workload while: Effects on visual search, discrimination, and decision making. Journal of experimental psychology: Applied. 2003;9:119-137. 4 Recarte M, Nunes L. Effects of verbal and special imagery tasks on eye fixation while driving. Journal of experimental psychology: Applied. 2000; 6:31-43 5 Chen L, Baker S, Braver E, Li G. Carrying passengers as a risk factor for crashes fatal to 16- and 17-year-old drivers. JAMA.2000;283:1582-1582 Competing interests: None declared |
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Suzanne P McEvoy, Senior Research Fellow The George Institute for International Health PO Box M201 Missenden Rd Sydney NSW 2050 Australia, Stevenson MR, McCartt AT, Woodward M
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We have read the responses to our study with interest and have a number of comments to make. Absolute versus relative risk: In this study we examined the effect of mobile phone use on the odds of having a crash requiring hospital attendance and demonstrated a fourfold increase in the likelihood of crashing. This is akin to calculating a relative risk, as distinct from an absolute risk. The study did not determine the absolute risk of crashing while using a mobile phone. Of course, the risk of having a crash during a given trip is usually very low and may vary by some degree depending on individual factors. Our findings suggest that using a mobile phone will increase that risk fourfold. Thus the absolute risk of having a crash while using a mobile phone remains low and this explains why many drivers have used a phone while driving but not had a crash while doing so. Despite this, given the large number of road injuries and deaths each year, coupled with the fact that the prevalence of mobile phone use varies and may be high in countries without legislation, we believe that a factor that increases the likelihood of a serious crash by fourfold is important. Other driver distractions: We recognise that mobile phone use is one of many potential distractions that may occur while driving. However, the availability of phone activity records during the hazard and control intervals makes this distraction particularly amenable to study using a case-crossover design. Furthermore, as the use of mobile phones continues to increase worldwide, the potential impact on road safety is a concern. Mobile phone use while driving has a number of potential effects: cognitive (conversation), visual (looking for the phone or at the display or keypad), auditory (listening to conversation) and manual (holding the phone or dialling a number). Under certain circumstances, any of these could lead to an adverse event. The role of additional occupants was raised. However, measuring conversation as an exposure using a case-crossover design is difficult as validating conversation during hazard and control intervals would be limited to self report. The presence and number of passengers has been associated with crashes resulting in driver deaths among teenagers.1 That said the effect of passengers varies by the age and gender of the driver and passenger, and among adult drivers, passengers can have a protective effect. Generally-speaking, as discussed by Dr Grove, a passenger is aware of the road conditions and can moderate his or her conversation as needed. The same cannot be said of a caller on the other end of a phone line. A recent on-road experimental study reported that in the most demanding urban roads conversations with passengers were suppressed, whereas mobile phone conversations were not.2 The study by Stutts and colleagues (2001)3 found that distraction was cited in 8.3% of crashes from the US National Accident Sampling System Crashworthiness Data System between 1995 and 1999 (presence of distraction unknown or no driver present in 35.9% of crashes) and Dr Grove has made some valuable observations that we will not repeat here. This study was not designed to provide risk estimates. For this, exposure data from an appropriate group of controls (or an appropriate control window) would have been needed for comparison. Moreover, the ownership and use of mobile phones has increased since that study was conducted, and police- reported data on driver distractions at the time of a crash may be incomplete, inconsistent and unreliable. Methodological issues: The only drivers we could include in the case-crossover analysis were those who had (1) driven during at least one control interval and (2) had phone activity records available. This is why the final number of drivers in the case-crossover analysis was 456. Of those, 40 (9%) had used a mobile phone in the period up to 10 minutes before the crash. We stress ‘up to’ because for those drivers who had driven less than 10 minutes prior to the crash (63%) we considered only phone activity during the stated duration of that trip (for both the hazard and corresponding control intervals). Of the 941 drivers who were interviewed, 72 (8%) reported using the phone during the trip in which they crashed (Table 1).4 Dr Lombardi raised the possibility of uncontrolled within-subject confounding in our study. This is an issue we discussed in the limitations section ‘circumstances of the control driving intervals may have differed from the crash driving interval’. While this problem is to an extent unavoidable, we did plan our study to explore some of these transient factors. Firstly, we collected information on the presence of other driver factors that may have contributed to the crash outcome including speed, alcohol, drugs and fatigue (Table 2).4 Secondly, we collected self reported data on weather conditions at the time of crash and during the control intervals and validated the information using rainfall reports from the Australian Bureau of Meteorology. While not presented in the paper, weather conditions (defined as wet or dry) did not alter the association between mobile phone use and crash. Finally, we asked drivers about the trip route during the hazard and control intervals. About half (47%) were travelling along the same route during both intervals. Culpability: We did consider driver culpability in planning the study and collected information on the circumstances of the crashes from drivers. While culpability was clear for some crashes, often it was not. Among those drivers involved in paired crashes (i.e. crashes in which two or more parties involved in the same crash were interviewed) accounts sometimes varied. As a result of the difficulty in assigning fault, we did not explore this further. Importantly, it is possible that the use of a mobile phone may impair a driver’s ability to avoid a crash, even if the driver is not at fault. We thank all respondents for their contributions. 1. Chen L-H, Baker SP, Braver ER, Li G. Carrying passengers as a risk factor for crashes fatal to 16- and 17-year old drivers. JAMA 2000;283:1578-82 2. Crundall D, Bains M, Chapman P, Underwood G. Regulating conversation during driving: a problem for mobile telephones? Transportation Research Part F 2005;8:197-211 3. Stutts JC, Reinfurt DW, Staplin L, Rodgman EA. The role of driver distraction in traffic crashes. Prepared for AAA Foundation for Traffic Safety, May 2001 4. McEvoy SP, Stevenson MR, McCartt AT, et al. Role of mobile phones in motor vehicle crashes resulting in hospital attendance: a case- crossover study. BMJ doi:10.1136/bmj.38537.397512.55 (published 12 July 2005) Competing interests: Authors of the study |
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Anthony G Harrison, OH&S consultant Adelaide, South Australia 5062
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While your paper relates to the use of mobile phones and their influence on motor vehicle accidents, I would be most interested to see, or hear, of any research that has been conducted into brain trauma with mobile phone useage, as it may relate to a rise in the incidence of epilepsy and sporadic hemangioma growth with seizure complications. This subject has been covered by different researchers from a generalised point of view and I suspect, behavioural issues were the main focus. My interest is from the OH&S perspective, where employees who are required to use mobile phones as part of their employment and are at twofold risk, the first being the issue discussed in your paper and the second is "forseeable misuse". I suspect that employers are not aware of the ramifications that may surface, given proof of an injury or health issue in respect of mandatory use of mobile phones in the course of employees duties. This, compounded by workers compensation law and civil law issues that would come into play could be very serious indeed, given that there have been a large number of studies past and current on this matter. Apart from the foregoing, the issues you have raised now clearly places every employer, who requires an employee to use a mobile phone whilst travelling in a company vehicle, in a situation of non compliance with work place safety law. Mobile phones are not the only culprits in this matter. Can I suggest that all manner of emegency service vehicles including police, plus taxi drivers would all find themselves in similar circumstances with two way radio communication. Add to the equation the long distance transport drivers who use CB and other radios as well as mobile phones and given your research, then there are problems of significant proportions. The whole issue of use of mobile phones in areas of injury risk is problematic, given the insistent and inherent nature of phone use. I suspect mobile phone use has been a lead contributor to many industrial accidents both minor and major. Competing interests: None declared |
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Jeremy C. Klein, physician Louisa, KY 41230
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To the Editor: The authors of the article concerning mobile phones have found that the risk of a crash increases if the driver uses a mobile phone. I won't dispute that finding; it's probably true. One wonders if there is an increased risk if the driver loads a CD, tunes the radio, or talks with passengers, but the risk of these activities was not addressed. The 'take-home message' of the article was that one ought not to talk on the cell phone while driving. The unstated subtext was that governments ought to ban the practice. Both messages are typically wrong-headed, failing to take into account the possible benefits of cell phone use while driving. While arguably the vast majority of cell phone calls made while driving are inconsequential, a substantial number are of more significance. I have fielded many a call concerning a medical problem while driving. I'm sure that busy executives have made hundreds, nay thousands, of critical business decisions on a cell phone while driving. Who can calculate the increased productivity opportunities available to the citizens of those states of the Union who are enlightened enough to allow them the freedom to use a cell phone while driving? We could substantially decrease crashes by limiting all speeds to 40 MPH; shall we do that, too? Sincerely, Jeremy Klein, M.D., F.A.A.F.P. Louisa, KY Competing interests: I own a cell phone and I use it while driving. |
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David Clegg, Process Engineer non-academic, Maidstone, UK
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I read McEvoy et al. with interest, although I share with other respondents concerns about how some people choose to interpret their valuable research. Road safety is a complex subject and many variables could be judged to contribute to, or to deduct from, the likelihood of being involved in a crash. So it is with driver distraction; an active mind is required for driving in complex conditions. However all conditions are not alike. An absolute statistic from the UK is that 15-20% of crashes were caused by driver sleepiness (ref below). The conclusions from one report clearly infer a link between a road that is "boring" and the likelihood of a crash. Perhaps some light radio, a conversant passenger, or indeed a call to a friend over a mobile telephone, could sometimes be considered a welcome distraction; even an officially recommended tool to reduce the 15- 20% of crashes from sleep-related causes? "...the greater the traffic density the greater the proportion of SRCs [sleep-related crashes]. On motorways, the opposite is true. This could be due to more vehicles on the road creating a less boring driving environment." An extract from 'Diane Flatley, Louise A Reyner and Jim A Horne: Sleep-related vehicle crashes - the relationship to traffic density', a publication by the Sleep Research Centre, Loughborough University, Loughborough LE11 3TU as appears on the UK Department for Transport website (viewed 20 Feb 07) www.dft.gov.uk/pgr/roadsafety/research/behavioural/thirteenthseminar/sleeprelatedvehiclecrashesth4698?page=1#1000 Competing interests: None declared |
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Ian Thomason, Sales Based at home DL15 OJJ
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I am at a loss to see how this study provides evidence that using a mobile phone whilst driving increases risk. The risk of being involved in an accident in the stusy is 100% Therefore any activity measured will show an increased risk i.e tuning a radio or changing a CD as presumably people do not crash each time they do this activity but may crash at another time having just completed the activity. The only valid study would involve a random selection of drivers over a period of time see how many had crashed and of those how many where using or had been using a mobile phone prior to the accident Competing interests: None declared |
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