PUBLIC EDUCATION AND MASS COMMUNICATIONS THE RATE OF MOTOR VEHICLE ACCIDENT INVOLVEMENT ASSOCIATED WITH PATTERNS OF ALCOHOL USE

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1 FO U R TH INTERNATIONAL CONFERENCE ON ALCOHOL AND TRA FFIC SAFETY SECTION I PUBLIC EDUCATION AND MASS COMMUNICATIONS Chairman: Alcoholism Research Foundation Toronto, Canada D r. W o l f g a n g S c h m i d t THE RATE OF MOTOR VEHICLE ACCIDENT INVOLVEMENT ASSOCIATED WITH PATTERNS OF ALCOHOL USE by B e r t h o l d B r e n n e r * t h e r e i s a n i n c r e a s i n g a m o u n t o f e v id e n c e t h a t t h e r e l a t i o n s h i p b e t w e e n p a t t e r n s o f a lc o h o l u s e a n d m o t o r v e h ic l e a c c i d e n t i n v o lv e m e n t is r a t h e r c o m p le x. Though m uch of the research on the relationship between drinking patterns and motor vehicle accidents is still underway or has yet to be undertaken, present findings an d observations, especially when pulled together and subject to a little further analysis, are beginning to provide a preview of what might be expected upon further, more careful study. At least two studies indicate that, as a category, drivers who are frequent, even daily, drinkers have a lower accident rate than less frequent drinkers. By means of a sample survey of Iowa adults, M ulford (1964) obtained inform ation on the drinking practices, average yearly mileage, and reportable driver accidents during the previous three years of a sample of Iowa drivers. H e reports a rate of 1.4 accidents per 100,000 miles among those who drink once a week or more frequently as compared to a rate of 1.5 among abstainers and a rate in excess of 2.0 for those who drink but usually do so less than once a week. * Research Sociologist, Epidemiology and Surveillance Branch, Division of Accident Prevention, Public H ealth Service, U nited States D epartm ent of H ealth, Education, and W elfare, W ashington, D.C. In a somewhat different type of study, Borkenstein and his associates (1964) obtained information on the drinking practices and other personal characteristics of both a sample of drivers involved in traffic accidents in Grand Rapids, M ichigan, and of a control sample of drivers similarly exposed to the probability of being involved in an accident. A comparison of the distribution of accident drivers in various drinking frequency categories with that expected on the basis of the distribution of the control drivers among those categories reveals that those who drink once a week or more frequently were about three fourths as likely to be involved in a traffic accident as those who do not drink or do so once a year or less. As in the Iowa study those with an inbetween drinking frequency (i.e., more than yearly but less than weekly) had the highest likelihood of accident involvement, though only slightly higher than those who do not drink or do so once a year or less. One-Sitting Drinkers However, if we consider only those drivers who usually consume substantial amounts of alcohol a t one sitting, the relationship between drinking frequency and accident in volvement is somewhat different. Thus, among the drivers in M ulford s study (1965) 57

2 58 PUBLIC EDUCATION, M ASS COM M UNICATIONS who usually drink at least three drinks (or equivalent amounts of wine or beer) at one sitting and who do so once a week or more h ad a rate of 1.9 reportable accidents per 100,000 miles; those who do so two or three times a month had a rate of 2.3 accidents per 100,000 miles; while those who do so one to twelve times a year had the highest rate of 3.0 accidents p er 100,000 miles. M ulford suggests that experience might make a driver more skillful at driving after drinking. C ertainly his d ata are not inconsistent with (but hardly sufficient evidence to really support) the hypothesis that a certain am ount of experience in driving w ith ap preciable alcohol levels lowers the risk in doing so. M ulford also suggests, as others have done in an attem p t to explain a somew hat lower accident rate for drivers with some as opposed to no alcohol in their system, that alcohol may reduce tensions in some drivers and thereby lower their risk of accident involvement. Some inform ation relevant to the possible tension-reducing effects of alcohol and possible differences in skill in driving is provided w hen the relative risk of accident involvem ent is computed from the distributions, by both drinking frequency and alcohol level, of the accident and control drivers in the G rand Rapids study (Borkenstein et al, 1964). Regardless of usual drinking frequency, the risk of accident involvement a p pears to increase steadily with alcohol level. Thus there appears to be no dip in the curve which describes the relationship between alcohol level and accident risk when usual drinking frequency is held constant. This does not necessarily mean, however, that certain types of drivers do not have their lowest rate of accident involvem ent a t some alcohol level slightly above zero. Only further research can reveal this. Infrequent Drinkers T he increase in accident involvement with increasing alcohol level tends to be greater for the infrequent than for the frequent drinkers. Thus those who report drinking yearly or less frequently appear to be about eight times more likely to become involved in an accident when they have an alcohol level of 0.05% or more, while those who report drinking weekly or more frequently are only about four times more likely to become in volved in an accident when they have an alcohol level in this range. This is true in spite of the fact th a t a much higher p ercentage of the frequent drinkers w ith alcohol levels above 0.05% had levels well in excess of 0.10%. T h e G rand Rapids d ata are not inconsistent with the hypothesis that the frequent drinker tends to attain some skill in driving after drinking but not enough to eliminate or reduce to insignificance the increase in risk of driving with an alcohol level approaching 0.10%. However, skill in driving after drinking cannot explain the finding that, even if only those in the zero alcohol category are considered, the frequent drinker s risk of accident involvement is still only about one half that of the infrequent drinker. Furthermore, the frequent drinker with an alcohol level in the range of 0.01% to 0.04% (or as high as 0.05% to 0.07% for the case of the daily drinker) is less likely to become involved in an accident than the infrequent drinker with zero alcohol. Apparently the frequent drinker is also favored by something not attributable to skill in driving after drinking perhaps he is simply a more sophisticated driver or somehow more able and/o r motivated to stay out of driver accidents. CBS Drivers Test An analysis of the background data for the 1,675 drivers constituting the studio audience for the recent CBS N ational D rivers Test, selected to be representative of drivers in Chicago, Los Angeles, New York, and Philadelphia, reveals that the estimated 23% who usually drink more than once or twice weekly are more likely to have been licensed to operate a motor vehicle for more than seven years, more likely to drive almost every day, more likely to drive as part of their job, and more likely to feel that they are better than average drivers. Those frequent drinkers are also more likely to be male, above 20 years of age, and college graduates. Though most of the drinking studies published to date do not present d ata on quantity of drinking by frequency of drinking, in a recent report on drinking in H artford, Connecticut, Cahalan, Cisin, Kirsh, and Newcomb (1965) do present data which show that three fourths of the respondents who reported that they drink daily or more frequently are persons who usually have only one to two drinks per sitting; in fact, over one third report never having as many as three drinks. Thus drivers who are frequent drinkers are mainly moderate drinkers, more experienced as drivers than less frequent drinkers, and

3 B E R T H O L D B R E N N E R 59 more likely to have characteristics (Borkenstein, et al, 1964, p. 219) which are related to lower driver-accident involvement. H ow ever, about 10% of the H artford respondents who drink daily or more frequently reported that they usually have five or more drinks per sitting, and about one half of these reported they do so three or more times per day. Also, in the G rand Rapids study the drivers who reported drinking weekly or more frequently include most of the approximately one-half per cent of drivers found driving with 0.15% or higher alcohol levels (Borkenstein, et al, 1964, p. 235) and probably also most of the drivers who are alcoholics. Alcoholic Drivers The rate of accident involvement among alcoholic drivers was studied by Schmidt, Smart, and Popham (1962) in Ontario. They found that a sample of clinically identified alcoholic drivers had 2.5 times as many reported traffic accidents or 1.8 times as many per mile driven as expected on the basis of data for the general population of drivers. This ratio of 1.8 is very close to the ratio of 1.7 found by W aller (1964) for California drivers w ith alcoholism. Actually this higher rate of driver accidents among alcoholics could reflect the net effect of several factors, such as, on the one hand, considerable experience w ith driving after drinking and, on the other hand, more frequent heavy drinking and behavior expressive of feelings of invulnerability, hostility, or self-destructiveness which, as Payne and Selzer (1962) suggest, may be released by drinking. Insofar as drinking releases feelings of self-destructiveness, one would expect alcoholics to have a rate of serious injury or death due to driver accidents which is more elevated than their rate of driver accidents. U nfortunately there appear to be no solid findings along these lines. However there are some findings which relate problem drinking and alcoholism to motor vehicle accidents involving serious or fatal injuries w ithout regard as to whether the problem drinker or alcoholic was injured as driver, passenger, or pedestrian. Bjerver, Goldberg, and L inda (1955) compared the distribution of drinking practices among traffic accident victims brought to a Stockholm city hospital to the distribution of drinking practices determined by a survey of the Swedish population. T h eir d ata indicate that the 3.5% of the Swedish population which they classified as either alcohol ad dicts or alcohol abusers are about six times as likely to become traffic accident victims as the bulk of the population, i.e., the m oderate users. I obtained similar results in a study of fatal accidents among San Francisco Bay Area alcoholics. Approximately 1,300 persons who came to the attention of C alifornia alcoholism treatm ent facilities and were selected for study by the California Division of Alcoholic Rehabilitation were followed for a total of over 7,000 m an years. These alcoholics were found to be four and one-half times as likely to die in a motor vehicle accident (i.e., as driver, passenger, or pedestrian) as expected on the basis of their age, sex, and Bay Area residence (that is, four and one-half times plus or minus a standard error of about one and one-half). H ow ever, it seems reasonable to hypothesize that this elevated rate of motor vehicle accident mortality among alcoholics reflects not only the im m ediate effects of alcohol and behavior released by alcohol b u t also the alcoholic s pattern of life, his state of health, and the care he receives when injured. SUMMARY To summarize, recent findings indicate that frequent drinkers have lower accident rates than less frequent drinkers or abstainers. As a category, frequent drinkers seem to consume moderate quantities of alcohol at one sitting, be more experienced drivers, and may also be more experienced in driving after drinking. However, frequent drinkers also have an increasing risk of accident involvement with increasing alcohol levels. In fact, the alcoholic driver, for example, has a definitely elevated accident rate. Another high risk category appears to be the infrequent drinker who consumes more than moderate am ounts of alcohol at one sitting. R e f e r e n c e s Bjerver, K. B., Goldberg, L. and Linda, P. (1955). Blood-Alcohol Levels in Hospitalized Victims of Traffic Accidents. Proceedings of the Second International Conference on Alcohol and Road Traffic, pp Brewer s W arehousing Co., L td., Toronto. Borkenstein, R. F., Crow ther, R. F., Shum ate, R. P., Ziel, W.B., and Zylman, R. (1964). The Role of the D rinking D river in Traffic Accidents. D e partm ent of Police A dm inistration, Indiana U niversity, Bloomington, Indiana. Cahalan, Don, Cisin, Ira H., Kirsch, A rthur D., and Newcomb, Carol (1965). Behavior and A tti

4 60 PUBLIC EDUCATION, M ASS COM M UNICATIONS tudes Related to D rinking in a M edium -Sized Urban C om m unity in N ew England. Report No. 2, Social Research Project, the George Washington University, W ashington, D. C. M ulford, H arold A. (1964). Iowa s Drinking Driver, 1961: W ith a M ethod for Identifying D rinking Drivers in a Survey Sample. Social Problems, Vol. 12, pp , (Fall, 1964). M ulford, H arold A. (1965). Unpublished tabulation from the 1961 Iowa Survey (prepared December 1965). Payne, Charles E., and Selzer, M elvin L. (1962). Traffic Accidents, Personality and Alcoholism; A Preliminary Study. Journal of Abdom inal Surgery, Vol. 4, pp (January, 1962). Schmidt, Wolfgang, Sm art, Reginald G., and Popham, Robert E. (1962). T he Role of Alcoholism in M otor Vehicle Accidents, Traffic Safety, Vol. 6, pp (December, 1962). Waller, Julian A. (1964). Alcohol and Traffic Accidents: Can the Gordian K not Be Broken? Selected Papers Presented at the 15th Annual M eeting, pp T he N orth American Association of Alcoholism Programs, W ashington, D. C. Question: Could you say something about the frequent and infrequent drinkers in terms of age o r social class? Do we know anything about th a t? Mr. Brenner: In the CBS National Drivers Test, those who were frequent drinkers, that is the studio audience, tended to be above 20 years of age, college graduates, and male. Question: T hat would be mainly adult? Mr. Brenner: It was an audience of drivers. It did include some under 20, but it was a random sample, a more or less of a random sample of drivers. In th a t sample, the frequent drinkers tended to be above 20 and college graduates. Question: You said before that when you controlled for frequency of drinking that there is a steady increase in accident probability in regard to the level of alcohol. Does this mean that when you look at each drinking frequency group separately that you don t get this dip from zero to.03%? Is this correct? Mr. Brenner: Exactly. Question: I am interested in the source of data concerning the frequent drinker versus the infrequent drinker. Have these been made from your personal studies, from police experience, or w hat is the source of data presented? DISCUSSION Mr. Brenner: I pulled together several things. I started by telling the accident rates of the frequent versus the infrequent drinkers, and th at was based on two studies, Iowa and G rand Rapids. T hen I tried to explain the findings, and I looked at other studies to get the characteristics of the frequent as compared to the infrequent drinker. One was the data from the CBS National Drivers Test, inform ation obtained on the studio audience. T h e other was the study in H a rtford, Connecticut, in which it was possible to see th at the frequent drinker for the most part is a moderate drinker. All this was pulled together in order to tell you what I had to tell you. Question: I can t understand what claim you make with the studio audience in regard to driving. This, if I rem em ber correctly, was a studio audience that was shown the movie, then they were asked questions, and you related this to the actual driving? Mr. Brenner: No, no. In looking for some information on what is the frequent drinker like, as far as driving experience is concerned, I looked around. Where can I find some information on w hat the frequent drinker is like insofar as his driving experience is concerned. It so happened that among the things asked of that studio audience were questions about their drinking habits and questions about their driving habits. I used that in order to tell you something about the driving experience of frequent drinkers. I used that data only for that. Question: Who substantiated this data that these people only had one or two drinks per se, or that they were moderate drinkers? Was there any substantiation on this? The guy says, I am a moderate drinker; I only drink two drinks. M r. Brenner: Well, in the Connecticut study the people reported themselves as frequent drinkers, and then they went on to report themselves in terms of their quantity. Now at this point we do not know exactly the reliability of self-reports of drinking habits. There is some indirect evidence that it is not bad. However, in this case, why should a person lie about his frequency but not about his quantity? In other words, the same people who reported themselves as frequent drinkers w ent on to report their quantity, and it turned out that the quantity tended to be usually no more than two drinks per sitting. Question: This m ight be outside the realm of your survey, or I may have missed it. Do you have any data or statistics showing the accident or violation frequency between nondrinkers and the sum total of infrequent and frequent drinkers? M r. Brenner: Yes, in Borkenstein s data I believe if one combines all the drinkers (now I haven t done this) and compares them to

5 B E R T H O L D B R E N N E R 61 the abstainers, one would find a lower rate among the drinkers as a group. But of course it is much more fruitful not to lump people quite that much. In fact, in further research, I think it is better not to speak in terms of frequent drinkers b u t to divide it into frequent drinkers who drink moderately and frequent drinkers who do not drink m oderately. Mr. Zylman: I am sorry that I wasn t here for the whole discussion but I think that I might be able to offer something that may be of interest. If I understand correctly, your discussion is why people who drink most often perhaps have less accidents. Is that the question under discussion? Actually this is what was found in the Grand Rapids study that the people who drink most frequently, and vice versa, and people who drink less often have the most accidents. We didn t understand this when we first found this out, so we ran related tests and found that in each case the people who drank most often came from the best driving groups, from the individual or different variables. For example, the people who drink most often came from the age group of 35 to 55, which is the best driving age. Of the sexes, the people who drank most often were the males, again the better of the two. Those who drank most often as far as education is concerned were again the people who were better educated. Conversely we found that the people who drank less were the very young and the very old. They drink the least often but they also come from the poorest driving age groups. As to who drinks least often among the occupational status groups, it was found th a t again the professional people tend to drink more often, whereas the unskilled laborer drinks less often. Again, you have this variance in driving capability between the top and the bottom. Thus we were able to justify that the people who drank most frequently have the least accidents, and people who drink the least often have more accidents. Chairm an Schmidt: May I ask if it has been attem pted to control in these com parisons for age, occupation, and social distinction? M r. Brenner: No, much more can be done with the G rand Rapids data than has been done. However, if age is an indication of driving experience, it m ight be better to go directly to driving experience rather than the control for driving experience rather than age, for example. Now there is not much about driving experience in the G rand Rapids data, which is one of the reasons I h ad to tu rn to other d ata to give some education as to w hat m ight be involved. As for the CBS data, unfortunately w hat is really needed is a study which includes m any of these variables which were not included in the G rand Rapids study.