A Review of the Literature on the
Effects of Low Doses of Alcohol on
Driving-Related Skills

April 2000

(PDF version)

A review of the scientific literature regarding the effects of alcohol on driving-related skills was conducted. One hundred and twelve articles - from 1981 to 1997 - were reviewed. Results were indexed by BAC and behavioral area and entered into a database. Two separate analyses were conducted. The first analysis determined the lowest BAC at which impairment is reliably present in driving-related skills. The second analysis determined the thresholds of impairment for each of twelve separate behavioral areas. It was concluded that:


Table of Contents

1. Introduction
2. Method
3. Results
  3.1 Overall Impairment
  3.2 Impairment, by Behavioral Areas
   
3.2.1
3.2.2

3.2.3

3.2.4
3.2.5
3.2.6
3.2.7
3.2.8
3.2.9
3.2.10
3.2.11
3.2.12
3.2.13
Driving and Flying: On the Road and Simulators
Divided Attention

Drowsiness

Vigilance Tasks
Tracking
Perception
Visual Functions
Cognitive Tasks
Psychomotor Skills
Choice Reaction Time
Simple Reaction Time
Critical Flicker Fusion
Aftereffects
4. Discussion and Conclusions
  4.1 Major Findings
4.2 Methodological Issues

4.3 Future Research

Reference List A [Articles used as reference]

Reference List B [Articles included in the review]

Appendix A [Tests results by behavioral area]

Appendix B [Data comparison between Moskowitz and Robinson (1988) and Moskowitz and Fiorentino (1999)]

List of Tables

List of Figures


1. Introduction

Historically, deterrence has been the principal approach for prevention of driving under the influence of alcohol. Legislatures have established blood alcohol concentration (BAC(1)) limits for driving and law enforcement agencies have enforced those laws. Scientists have contributed to the establishment of BAC limits with data from experimental and epidemiological studies to identify the alcohol levels which produce driving skills impairment and increased crash rates.

In the scientific literature, impairment refers to a statistically significant decrease in performance under alcohol treatment from the performance level exhibited under placebo treatment. To reach statistical significance, performance differences in subjects under the two treatments must be reliable and substantial in magnitude.

In a report published by the National Highway Traffic Safety Administration (NHTSA), Moskowitz and Robinson (1988) reviewed the experimental literature from the 1950's through 1985 on alcohol effects on driving related skills performance. The report summarized 177 studies which met the following criteria for inclusion: Placebo treatments, statistical significance, and the ability to determine the BAC at the time of testing. Overall, 21% of the studies reported performance impairment by 0.04 g/dl, 34% by 0.05 g/dl, 66% by 0.08 g/dl and nearly all by 0.10 g/dl. The skills performance measures were organized into 10 response categories. The BAC at which impairment was first measured and the percent of studies reporting impairment at the various BACs differed by response area. Divided attention, visual functions, and tracking were impaired in the 0.01-0.02 g/dl range, with the number of studies reporting impairment increasing rapidly with increasing BACs. On the other hand, the impairment of simple reaction time and psychomotor measures began at higher BACs. Simple reaction time in particular was found to be an insensitive and unreliable measure.

Moskowitz and Robinson criticized studies which examined performance at one BAC only since a report of impairment at a single BAC sheds no light on the question of whether lower BACs might also be impairing. They concluded that the data identified no threshold BAC below which impairment does not occur. They also concluded that the scientific evidence supported a reduction of the BAC limit for driving to 0.05 g/dl. Finally, to facilitate the classification of examined behaviors, they urged investigators to include fuller descriptions of methods and procedures in reporting future research over a wider range of BACs.

Subsequently Kruger, et al., (1990) in Germany, performed a literature review capturing the European non-English language literature (English summary in Kruger, 1993). The Kruger, et al., review encompassed studies of alcohol effects on subjective reactions such as mood, and social relations, as well as on skills performance. The studies were organized into categories including: subjective reactions, social behaviors, psycho-physical functions, automatic behaviors, controlled behaviors, and driving. The terms automatic and controlled are taken from cognitive psychology theory. Automatic behaviors refer to over-learned tasks which require little conscious mental activity (easy tracking, simple and choice reaction time, mental arithmetic, concentrated attention, etc.). Controlled behaviors involve a greater mental workload (difficult tracking, divided attention tasks, information processing, etc.). Studies of controlled behaviors report impairment beginning at 0.03 g/dl. Impairment appears at somewhat higher BACs for automatic behaviors. The authors concluded that social and controlled behaviors are impaired at 0.030-0.049 g/dl in actual traffic whereas automatic behaviors are not impaired before 0.05 g/dl.

Holloway (1994, 1995) used Kruger's schema in a review for the period 1985 - 1993. In agreement with Kruger, he found that subjective effects and controlled behaviors are affected by alcohol at lower BACs than psycho-physical or automatic behaviors. He reported that 70 to 80% of studies examining controlled behavior and subjective intoxication reported impairment by BACs at or below 0.04 g/dl.

Determining whether a behavior is automatic or controlled, however, can be difficult. Shinar, et al., (1998), for example, demonstrated that the frequent description of gear shifting in a manual transmission vehicle, as an "automatic" process was erroneous. Subjects showed decreased detection of roadside signs during manual shifting in comparison with automatic transmission cars. This is not to argue the potential value of the cognitive psychology model of driving behavior, but as Ranney's (1994) review of driving behavior models noted, accurate assignment of driving activities as controlled or automatic awaits further research. Moskowitz and Robinson (1988) noted the difficulty of assigning studies to behavioral areas given that reports of experimental methods and procedures often are quite limited. As an example, driving simulator studies vary greatly in the types of roads traversed, the degree of interacting traffic, the length of travel, and mental workload. Such variability, which is obvious in simulators, also exists in other measured behaviors. To expand the boundaries of response categories into theoretical groupings without empirical studies validating that placement would only inflate the problem. A fully satisfactory resolution awaits a better taxonomy of behavior which, coupled with better specification and execution of experimental studies, will permit organization of diverse studies into theoretical formats.

This review examines the 1981 to 1998 literature on driving related behavior primarily under low BACs. The behavioral response categories have been organized in a form slightly different from that used by Moskowitz and Robinson (1988). Two caveats apply to the 13 categories of driving-related behaviors in the categorization scheme used in this review. First, note that assignment of tasks to the behavioral categories is arbitrary to some degree and, in some cases, is different from the investigator's categorization. For example, results from an experiment which reported that subjects were required to perform two tracking tasks simultaneously appear under divided attention rather than under tracking. Second, even within each of the 13 behavioral categories, there is great variability in experimental tasks and corresponding demands on the subjects. An attempt to incorporate the studies into larger categories of a theoretical schema would serve to increase within-category variability and would result in a blurring of distinctions between categories.

1. Alcohol in blood is measured in terms of weight per volume. In the US, BACs are typically reported in grams of absolute alcohol per deciliter of whole blood (0.08 g/dl). The symbol "%" is frequently used to denote g/dl. Note, however, that the "%" symbol is not a true percentage since it is describing a measure of weight in a measure of volume.

In this paper, g/dl is the measure utilized. Th values remain the same if the symbol "%" is substituted to g/dl. Other countries frequently use mg/dl (e.g., 80 mg/dl) or g/l (e.g., 0.8 g/l) as their units of measure.

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2. Method

As in the Moskowitz & Robinson (1988) review, the search was limited to experimental measures of skills performance. Without denying the importance of motivational and subjective behaviors as possible factors interacting with alcohol effects on safety, it was our decision that including these response variables would unduly broaden the scope of the review. No one denies, for example, that alcohol increases aggression; there is adequate literature to demonstrate that. What is less clear is how the increased aggressiveness under alcohol would interact with driving behavior. The study of the effects of alcohol on motivation, emotion, etc., therefore, deserves a separate review. This review is confined to more clearly defined measurable variables that are relevant to driving.

Using various search engines, a wide computer search of the literature reporting the effects of alcohol on driving skills was conducted. Abstracts were obtained for 1733 titles produced by the computer search. Based on the content of these abstracts, 358 articles were identified for retrieval and further review. Seventy-three of selected publications were not available.

The 285 published articles retrieved were evaluated to determine whether they met the following, pre-determined inclusion criteria:

The evaluation determined that 112 studies met the review's inclusion criteria. These 112 articles were reviewed and indexed by driving behavior and BAC, and the pertinent data from each article were entered into a computer data base. Table 1 provides a short description of the behavioral tasks included in the 112 studies by the 13 behavioral domain areas which categorized those studies. It lists the number of articles in each behavioral domain and the number of BAC levels tested across those studies within the domain.


Table 1: Behavioral Areas and Tasks, by Articles and BAC
Domain Tasks Number of Articles Number of BAC Levels
Aftereffects Testing measured residual alcohol effects on a drinker's performance following a drinking session and the drinker's return to zero BAC. Various tasks from all other domains were used. 12 25
Cognitive Tasks Digit-symbol substitution, mathematical and verbal reasoning, memory, pattern recognition, visual backward masking, card sorting. 31 145
Critical Flicker Fusion Determination of the lowest frequency at which a flickering on-off light appears to be constant. 7 18
Divided Attention Simultaneous performance of two or more tasks such as tracking, visual search, number monitoring, and detection of auditory stimuli. 18 52
Driving Skills Actual driving, simulated driving, simulated flight, motorcycle simulator. 25 50
Perception Detection of visual and/or auditory stimuli, time estimation, traffic hazard perception, anticipation time. 12 35
Psychomotor tasks Finger tapping, body balance, hand steadiness, drill press operation, assembly of electronic parts. 18 57
Reaction time - Choice Choice reaction time, choice reaction time with auditory distraction. 15 37
Reaction time - Simple Single known stimulus with a single response. 5 20
Tracking Pursuit tracking, compensatory tracking, critical tracking. 11 23
Vigilance Vigilance. 9 18
Visual Functions Contrast sensitivity, depth perception, smooth pursuit, saccadic peak velocity, saccadic latency, saccadic inaccuracy, nystagmus, etc. 19 63
Drowsiness Multiple sleep latency test, repeated test of sustained wakefulness. 6 13
Total   112 556
Note: Many articles covered more than one behavioral area

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3. Results

The following sections present the results of two approaches in reviewing the literature. The first approach presents the data for impairment across all behavioral areas, counting the number of studies with each study counted once at the lowest BAC for which impairment was found. Most studies, however, reported on more than a single measure and, in fact, several reported findings for multiple driving skills across different behavioral areas (i.e., vigilance and divided attention and psychomotor skills). In addition, several studies reported tests of performance in different behavioral areas and at different BACs. The second analysis, which focused on specific behavioral areas, examined reports of more numerous behavioral tests across BACs.

3.1. Overall Impairment

The following analysis is based on 109 of 112 reviewed studies. Three studies were not included. The following is a brief discussion on the rationale for the exclusions.

Willumeit, et al., (1984) described their apparatus as a driving simulator, but it is better described as a tracking device. Subjects moved a light signal in a horizontal plane to coincide with the appearance of a light stimulus. The light signal appeared in one of 50 possible blocks along a horizontal scale. Each appearance of the step signal was preceded by one of two arrows to indicate the direction of stimulus appearance. The study treatments were alcohol, two benzodiazepines, and a beta-blocker. The three drugs and a placebo were administered with and without alcohol for eight treatments total. At 0.05 g/dl BAC, there was no difference between alcohol and placebo treatments. Ten mg diazepam also failed to impair in comparison to placebo. Since this analysis focused on the BAC threshold for impairment, studies in which impairment was not found at any BAC were excluded, whether the result was due to instrument insensitivity, flawed methodology or other cause.

A study by McMillen, et al. (1989), which is described as a study of risk taking in a driving simulator, also was dropped from the analysis. The simulator was a video driving game (Sego, Model 100), and dependent measures were number of lane changes, cars passed, and time at maximum speed during a 4.5 minute drive. A mean BAC of 0.07 g/dl had no effect on any response measure. These results are at variance with studies which report alcohol effects on risk taking (Cohen, et al.,1958; Light and Keiper,1969; Fromme,1997). Similar research has reported that alcohol affects speed selection. Since McMillen, et al. (1989) reported no alcohol effects at the tested BACs, this study was not included in the analysis on the assumption that the measures obtained with the video driving game were insensitive to alcohol.

Finally, one other study was not included, although it did report a response measure sensitive to the effects of alcohol. Yesavage and Leirer (1986) examined the aftereffects of alcohol ingestion. Although other studies of aftereffects include data obtained before subjects' BACs dropped to zero, this one did not. Since it only measured performance at zero BAC, the results do not pertain to the issue of BACs at which alcohol impairment first appears.

Figure 1, based on 109 studies, shows the number of studies reporting impairment by the lowest BAC at which impairment appeared. Note that the BAC categories used here are slightly different than those in the Moskowitz and Robinson study. Here each BAC category ends with a 9 (e.g., 0.020-0.029 g/dl) whereas Moskowitz and Robinson used BAC categories ending in zero(e.g., 0.021-0.030 g/dl). Twenty-seven percent of the studies reported impairment by 0.039 g/dl, 47% by 0.049 g/dl and 92% by 0.079 g/dl. The impairment appeared in one or more of the response variables examined in the study. As shown in Tables B1 and B2 in Appendix B, impairment was reported by more studies and for lower BAC than in the 1988 review by Moskowitz and Robinson. The difference may be accounted for in two ways. First, pre-1988 studies included very few which examined more than one BAC. If impairment is reported only for a single selected BAC, no inference can be drawn about alcohol effects at lower BACs. In this review of more recent literature, the majority of studies have examined multiple BACs, which permits the identification of lower BAC at which impairment appears. Second, the methods and instruments used by researchers in this past decade have improved.

Figure1. Chart of Number of studies reporting impairment (109), by loweat BAC at which impairment was found.
Figure 1. Number of studies reporting impairment (109), by the lowest BAC at which was found.

3.2. Impairment, by Behavioral Areas

The following analysis is based on all 112 reviewed studies.Figure 2 summarizes the number of test results by BAC for all the tasks examined.Note that these are not the number of studies, but the total number of tasks across experimental conditions for all studies. In some cases, impairment was reported at BACs as low as 0.009 g/dl. By the time subjects reach BACs of 0.030 g/dl, the number of impaired behavioral areas is greater than the number not impaired. As BACs increase, the number of areas showing impairment also increase. Clearly, the measurement of impairment at very low BACs requires highly sensitive measures. Also, as will be seen later, some behavioral areas are far more sensitive to the effects of alcohol than others. Even within a given area, there was considerable variation in the BAC at which impairment was first reported. As previously noted, it is relevant that experimental procedures vary greatly since procedures affect the sensitivity of response measures. The following are comments on the results within each behavioral areas.

Figure2. Chart of Summary of behavioral tests results (556). Aftereffects are reported at zero BAC.
Figure 2. Summary of 556 behavioral test results. Aftereffects are reported at zero BAC

3.2.1. Driving and Flying: On the Road and Simulators (Figure 3, Table 1 in Appendix A).

Twenty-five studies produced a total of 50 behavioral tests. Impairment was reported for BACs below 0.01 g/dl. As shown in Figure 3, nearly all driving and flying simulator studies or on-the-road studies of driving reported impairment by alcohol. The lowest BAC at which impairment was found (0.001 g/dl) was reported by Morrow et al. (1990) who, using a flying simulator, required subjects to integrate information about aircraft, traffic, and weather conditions; maneuver the aircraft along a dynamic flight path; and maintain radio communications.

McMillen et al. (1989) reported the highest BAC at which impairment was not found (0.070 g/dl). The methodological and instrumental problems in that study were discussed in the preceding section.

In the decade since the Moskowitz and Robinson report was published, the sensitivity, reliability and face validity of driving and flying simulators have improved. Driving simulators now present scenarios which better reflect the mental workload of actual driving, which may account for their increased sensitivity to alcohol. Note that subjects in the Morrow et al. study, which reported impairment at 0.001 g/dl, were required to perform multiple tasks simultaneously in a divided attention paradigm.

3.2.2. Divided Attention (Figure 3, Table 2 in Appendix A)

Eighteen studies of divided attention yielded 52 behavioral tests. In general, experimental tasks aimed at measuring the ability to divide attention are sensitive to alcohol effects, beginning at BACs of 0.005-0.010 g/dl. Divided attention tests require subjects to perform two tasks concurrently, and most use a central tracking task and a peripheral visual search task. This approach is appropriate since it models the divided attention characteristics of driving; tracking can be considered analogous to maintaining lane position and visual search corresponds to monitoring the environment. Roehrs et al.(1994) used this configuration and measured impairment at BACs as low as 0.005 g/dl.

A few divided attention tasks use apparatus which requires subjects to simultaneously monitor number displays in central and peripheral vision. This approach appears less sensitive than the combined tracking-visual search task, possibly due to the similarity of the two number tasks and the lack of a continuous component (such as tracking).

3.2.3. Drowsiness (Figure 3, Table 3 in Appendix A)

Although wakefulness is not a measure of skills performance, it is an essential requirement for safe driving. Sleep, or more accurately drowsy driving due to sleep loss or deprivation, has been identified as a contributing variable to crashes, and its potential interaction with alcohol is of import because most alcohol-related crashes occur at night, when drivers are more likely to need sleep.

Figure3. Charts of Behavioral test results, by behavioral area.

Six studies of the effects of alcohol on drowsiness produced 13 behavioral test reports of which 11 showed impairment. The findings were obtained with two tests, the multiple sleep latency test (MSLT) and the repeated test of sustained wakefulness (RTSW). The MSLT is a highly standardized measure of physiological sleep tendency. Subjects are connected to polysomnographic equipment, and are given the opportunity to fall asleep at regular intervals. Sleep latency is a measure of elapsed time from when the subjects are told to fall asleep to the occurrence of the first epoch of any sleep stage. The RTSW also measures physiological sleep tendency, but in this test subjects are instructed to resist falling sleep. It has not been validated as extensively as the MSLT.

In general, wakefulness tests were found to be very sensitive to the effects of alcohol. The time to fall asleep was shorter with BACs of 0.010 g/dl and higher, except for two instances, one time at 0.021 g/dl and the other at 0.034 g/dl. The latter result was obtained with the RTSW, arguably the less sensitive of the two test.

3.2.4. Vigilance Tasks (Figure 3, Table 4 in Appendix A)

Nine vigilance studies produced 18 behavioral test results, of which 16 showed alcohol impairment. None of the studies reviewed examined vigilance at BACs below 0.020 g/dl, and two studies reported that there was no impairment at BACs of 0.021 and 0.028 g/dl. Note that one of the studies (Gustafson, 1986) required the subjects to press a switch as rapidly as possible when a tone of 1000 hz at 90 db was presented. A tone of that magnitude might alert subjects and offset the effects of alcohol, particularly at low BACs. At BACs of 0.030 g/dl and above, impairment was reported consistently across all studies.

Vigilance studies which had been published in the literature at the time of the Moskowitz and Robinson review were considerably less likely to show impairment by alcohol. Clearly, since then, more sensitive measures of vigilance have been developed.

3.2.5. Tracking (Figure 3, Table 5 in Appendix A)

Eleven studies of tracking produced 23 behavioral test results. Overall, the results indicated that threshold of impairment varied as a function of the type of tracking task used.


3.2.6. Perception (Figure 3, Table 6 in Appendix A)

Twelve studies produced 35 test results. Studies in this category used tasks which differed widely in terms of information processing requirements. Tasks included time estimation, auditory signal detection, visual search, pattern recognition, and traffic hazard perception. The diversity of mental workload is believed to underlie the reported diversity in alcohol sensitivity. In general, the evidence indicates a lack of significant impairment of perceptual abilities below BACs of 0.080 g/dl, although there were some reports of impairment at lower BACs. The lowest impairing BAC (0.037 g/dl) was reported by Lapp et al. (1994), and the highest BAC at which impairment was not found (0.080 g/dl) was reported by Heishman et al., (1997). Interestingly, both of these findings were both obtained with time production/estimation tasks.

Moskowitz and Robinson found perception tasks to be far more sensitive to alcohol than the previous paragraph reports. However, the studies in that earlier review reported on the examination of behaviors quite unlike those examined by investigators in the more recent studies reviewed here.

3.2.7. Visual Functions (Figure 4, Table 7 in Appendix A)

Nineteen studies examined alcohol effects on visual functions, producing a total of 63 behavioral tests. In general, the reports of impairment were consistent at 0.030 g/dl and higher. Many different behavioral functions were included in this category, including visual acuity, contrast sensitivity, eye movements and ocular motor control. Visual acuity appears not to be affected by alcohol below 0.070 g/dl BAC, a finding which is consistent with earlier studies. On the other hand, contrast sensitivity (the ability to discern spatially distinct luminance differences) and tests of oculomotor control were impaired by alcohol at 0.030 g/dl. Mattila et al. (1992), for example, found that subjects' coordination of extra-ocular muscles was significantly affected at 0.026 g/dl.

3.2.8. Cognitive Tasks (Figure 4, Table 8 in Appendix A)

This category encompassed 31 diverse studies with 145 test reports. The tasks varied considerably in assumed information processing characteristics and in sensitivity to alcohol. So perhaps it is not surprising that the appearance of impairment by alcohol varied from as low as 0.005 g/dl to as high as 0.160 g/dl.

Figure 4. Charts of Behavioral test results, by behavioral area.

Studies of backward masking, a well established measure of information processing rate or perceptual speed, found impairment at 0.030 g/dl (Wilkinson, 1995). Digit-symbol substitution tasks, on the other hand, did not reliably show a deficit until BACs above 0.060 g/dl. Even higher thresholds applied to card sorting, grammatical reasoning, and the Sternberg memory task. Card sorting tests were not generally affected by BACs below 0.090 g/dl, although Lyvers & Maltzman (1991) reported impairment at BACs below 0.050 g/dl. Grammatical and mathematical reasoning tests were not generally affected by BACs below 0.080 g/dl, although Heishman et al. (1997) and Kennedy et al. (1993) reported impairment at BACs of 0.025 g/dl and 0.060 g/dl, respectively. Memory tests, including the Sternberg memory tests, which require subjects to memorize a set of symbols (letters or numbers) and to later determine whether a short sequence of symbols contains the memorized set, were not affected by BACs below 0.060 g/dl. A notable exception was the results reported by Millar et al. (1995) who reported impairment at BACs below 0.020 g/dl in selective reminding tasks.

It is difficult to summarize the evidence concerning alcohol effects on cognitive tasks. As can be recognized, the tasks discussed above have little in common behaviorally, and some are complex and likely require more than one cognitive function.

3.2.9. Psychomotor Skills (Figure 4, Table 9 in Appendix A)

Eighteen studies of the effects of alcohol on psychomotor skills produced 57 tests, 33 of which found impairment and 24 did not. Because of the diverse nature of psychomotor skills and the tests of those skills, it is difficult to establish a threshold for alcohol effects. For that reason, the results have been further divided into three task groups: Finger tapping, body balance, and skilled physical tasks.

3.2.10. Choice Reaction Time (Figure 4, Table 10 in Appendix A)

Choice reaction time experiments use multiple stimuli and response possibilities, thereby placing a greater information processing load on subjects than simple reaction time. Fifteen choice reaction time studies produced 37 behavioral test results. Although most choice reaction time studies showed impairment by alcohol, it was only at 0.060 g/dl that there were more reports of impairment than of no impairment. By 0.080 g/dl, however, more than 80% of the studies reported evidence of complex reaction time impairment. Differences in findings are attributable to a wide range of stimulus and response conditions. There is no doubt that choice reaction time is more sensitive to the effects of alcohol than simple reaction time, but a variety of experimental methods under this single rubric leads to differing findings.

3.2.11. Simple Reaction Time (Figure 4, Table 11 in Appendix A)

Five studies with 20 test results at various BACs examined alcohol effects on simple reaction time. Moskowitz & Robinson (1988) concluded that simple reaction time is an insensitive measure. The experiments involve repetitive testing with a single known stimulus and a single known response. Subjects not only know where and what the stimulus is and what the single response option is, they may also be cued when a stimulus is about to occur. As Figure 4 suggests, most experiments using simple reaction time as a measure failed to show any alcohol effects. These tasks, of course, are unrelated to the reaction time demands of actual driving where it is rare for a drivers to know about the initiating stimulus in advance or to know what response will be required.

3.2.12. Critical Flicker Fusion (Figure 4, Table 12 in Appendix A)

In Critical Flicker Fusion (CFF) a subject indicates the threshold at which he/she perceives a flickering on/off light to be constant; that is, not flickering anymore. It has frequently been used in studies of psychoactive drugs. In seven studies at 18 BACs, CFF was an extremely insensitive measure for which impairment occurred only above 0.100 g/dl BAC. Continued use of this test to examine the effects of alcohol on driving related behavior is unwarranted, both because of its insensitivity to alcohol, but also because there is no known relationship to driving.

3.2.13. Aftereffects (Table 13 in Appendix A)

The research area of alcohol aftereffects emerged during the last decade. It examines the residual effects after a positive BAC has declined to zero. Aftereffects are distinguished from hangovers, which are experienced subjectively, and may affect performance without subjective reaction. Twelve studies examined aftereffects of alcohol and produced 25 behavioral test results, of which six reported impairment and 19 did not. A variety of measures included tracking, body sway, eye movements, simple reaction time, critical flicker fusion, symbol copying and others. In the reported impairment, however, only three response measures were used: the MSLT, a flight simulator, and a measure of angular motion.

Reported findings appear to be a direct function of the measures used to study aftereffects. Angular motion, for example, as studied by Ross et al. (1995) used unusually elaborate and complex testing equipment. Subjects were seated in a compartment which rotated clockwise until they reported that the sensation of motion had stopped. Starting from 3 rpm, thresholds for detection of right turns (acceleration of the compartment) and for detection of left turns (deceleration of the compartment) were determined for each individual subject. The subjects' task also included calling out the direction of the turn while depressing a yoke button until the turning ceased, maintaining constant altitude by observing the altimeter and vertical speed indicator, making appropriate yoke inputs, and monitoring for two numbers on a separate visual search task. A significant shift in the threshold of angular motion was observed after the subjects ingested small quantities of alcohol and after a return to zero BAC.

Most other studies used less sensitive measures. Although this area of study has no bearing on the issue of BAC limits, the findings of impairment as a consequence of aftereffects is a traffic safety issue which needs further study.


4. Discussion

4.1 Major Findings

This review of the literature provides strong evidence that impairment of some driving-related skills begins with any departure from zero BAC. By 0.050 g/dl, the majority of studies have reported impairment by alcohol. By BACs of 0.080 g/dl, 94% of the studies reviewed reported impairment. These results include behavioral response areas which are on the one hand insensitive to the effects of alcohol and on the other hand scarcely representative of the demands of driving, such as critical flicker fusion and simple reaction time.

There is evidence that behavioral areas differ in their relative sensitivity to the impairing effects of alcohol. This is in agreement with Moskowitz and Robinson (1988), Kruger (1990), Holloway (1994), and other investigators. Table 2 reports the lowest BACs at which different behavioral areas exhibit impairment.

Table 2: BAC and Impairment, by Behavioral Area
BAC
(g/dl)
By Lowest BAC at Which
Impairment Was Found

By First BAC at Which
50% or More of Behavioral Tests
Indicated Consistent Impairment

0.100 Critical Flicker Fusion Simple Reaction Time, Critical Flicker Fusion
0.090-0.099    
0.080-0.089    
0.070-0.079    
0.060-0.069   Cognitive Tasks, Psychomotor Skills, Choice Reaction Time
0.050-0.059   Tracking
0.040-0.049 Simple Reaction Time Perception, Visual Functions
0.030-0.039 Vigilance, Perception Vigilance
0.020-0.029 Choice Reaction Time, Visual Functions  
0.010-0.019 Drowsiness, Psychomotor Skills, Cognitive Tasks, Tracking Drowsiness
0.001-0.009 Driving, Flying, Divided Attention Driving, Flying, Divided Attention

The first column lists behavioral areas by the lowest BAC at which impairment was found. The second column lists behavioral areas by the first BAC at which 50% of the behavioral tests indicated impairment. That is, the point at which the majority of behavioral tests showed impairment. Note that, with the exceptions of simple reaction time and critical flicker fusion, all driving-related skills exhibited impairment by 0.070 g/dl in more than 50% of tests.

This review supports the suggestion by Ferrara et al. (1993) that discrepancies in test results reflect a lack of standardization in testing methods and that failures to find alcohol impairment at low BACs may be attributable to the use of tasks which are not sensitive to behavioral changes caused by alcohol. If studies only involving driving (in simulators and on the road), simulated piloting, divided attention, and vigilance are examined, 73% of the test results in those areas exhibited impairment by 0.039 g/dl. Including tracking and drowsiness, 65% of the tests performed by 0.039 g/dl showed impairment. Decisions with regard to BAC limit should not be determined on the basis of behavioral areas that are relatively insensitive to alcohol. Crash risk is determined by impairments of those behavioral areas which are important determinants of driving and which are the most sensitive to alcohol.

Virtually all subjects tested in the studies reviewed here exhibited impairment on some critical driving measure by the time they reached 0.080 g/dl.

4.2. Methodological Issues

It is impossible for a reviewer who is not physically present at the execution of the study to stipulate beyond the authors designation how to classify some of these studies. Unfortunately, the variability in results between studies, even within a category, limit the ability to provide advice on the use of response measures to investigate alcohol effects on driving. Researchers in psychometrics, who develop new behavioral tests, are obligated to provide adequate evidence of the validity and reliability of these tests before they are used in measuring behavioral functions in patients. It would appear incumbent on experimental investigators of alcohol and other drug effects to at least provide some defense as to the adequacy of their response measures. Hopefully, this review will contribute to putting to rest the utilization of critical flicker fusion and simple reaction time as measures for examining alcohol effects.

In discussing the imposition of BAC limits, the issue has been raised that not every individual is necessarily impaired at that specific limit. It should be noted that the BAC at which every single individual is impaired has not been an issue in any of the above studies. The requirements of experimental design precludes doing such an analysis. None of the behavioral variables examined, except perhaps for drowsiness, is so over-learned that there are no order or practice effects during an experiment. The majority of studies reported are within-subjects designs where each subject acts as his/her control and where the order of treatment, alcohol or placebo, is counterbalanced. Some subjects receive the alcohol treatment on the second day after their performance has improved from the first placebo treatment day. This makes it difficult to demonstrate impairment in all individuals, since the practice or order effect and the alcohol treatment effect are confounded. It is possible to make the assertion that subjects were impaired by 0.08 g/dl because a substantial majority of subjects would have to exhibit impairment in order for the study to report statistical significance. Thus, even for studies which have reported impairment at 0.010 g/dl, nearly all subjects would have had to demonstrate impairment.

4.3. Future Research

A valuable future area of research would be to examine the interaction of alcohol with sleep deprivation and circadian rhythms. There is strong evidence, produced by the studies on drowsiness, that ability to remain alert and functioning is impaired by alcohol. Nearly all the experiments included in this review involving drowsiness were performed during the day. Noting that the majority of alcohol-related crashes occur at night, it is clear that additional research on time of day is called for.

An additional area which should be examined further is the effects of alcohol on subjective responses. This would include effects on emotion, motivation and judgment. Many theories of driver behavior emphasize motivational and attitudinal factors as important determinants of safety. There is experimental literature demonstrating alcohol effects on aggression and other subjective behaviors. If the importance of the topic is granted, it would appear advisable to review the literature on the role of emotional/motivational factors in driving and the effects of alcohol on such factors. At this point in time, the literature appears incomplete. Note that both Kruger (1990), and Holloway (1994) indicated that subjective reactions were among the most likely to demonstrate impairment at low BACs.


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Appendix A
Tests Results, by Behavioral Area

Table A1
Summary of Test Results for Driving/Piloting
Author Year Experimental Task BAC Impairment
Morrow et al. 1990 Flight simulator (severe altitude errors, summary score) 0.001 Yes
Morrow et al. 1993 Flight simulator (severe altitude errors, summary score) 0.002 Yes
Roehrs et al 1994a Driving simulator (left deviations, right deviations, absolute deviations, points out of range) 0.013 Yes
Morrow et al. 1990 Flight simulator (radio performance, summary score) 0.017 Yes
Louwerens et al. 1987 Driving (standard deviation of lane position, speed variability) 0.024 No
Billings et al. 1991 Flight simulator (serious errors) 0.025 Yes
West et al 1993 Driving (hazard perception) 0.025 Yes
Ross et al. 1992 Flight simulator (instrument departure procedural errors) 0.030 Yes
Willumeit et al. 1984 Driving simulator (composite score) 0.032 No
Ross et al. 1992 Flight simulator (intersection holding errors, basic IFR flight control errors, degree of error in position reports, failure to question clearance, communication errors) 0.033 Yes
Ross et al. 1992 Flight simulator (instrument departure procedural errors) 0.034 Yes
Ross et al. 1992 Flight simulator (intersection holding errors, basic IFR flight control errors, degree of error in position reports, failure to question clearance, communication errors) 0.035 Yes
Gengo et al. 1990 Driving simulator (standard deviation of reaction time) 0.040 Yes
Mongrain 1989 Driving simulator 0.040 Yes
Ross & Mundt 1988 Flight simulator (composite score) 0.040 Yes
Brookhuis & De Waard 1993 Driving (car following, standard deviation of lane position) 0.041 Yes
Morrow et al. 1990 Flight simulator 0.041 Yes
Morrow et al. 1993 Flight simulator (severe altitude errors, summary score) 0.042 Yes
Vermeeren & O'Hanlon 1998 Driving (standard deviation of lane position) 0.045 Yes
Roehrs et al 1994a Driving simulator (left deviations, right deviations, absolute deviations, points out of range) 0.049 Yes
Willumeit et al. 1984 Driving simulator (composite score) 0.049 No
Smiley et al. 1987 Driving (speed on open road curves, peripheral stimuli detected, and standard deviation of velocity on runway curves) 0.050 Yes
West et al 1993 Driving (hazard perception) 0.050 Yes
Willumeit et al. 1984 Driving simulator (composite score) 0.050 No
Gawron & Ranney 1988 Driving (curve lateral position deviation, straight lateral position deviation, right road departure, curve speed deviation, straight speed deviation, time between same-side departures) 0.053 Yes
Gawron & Ranney 1988 Driving simulator (lateral position, number of times over the speed limit) 0.053 Yes
Allen 1996 Driving simulator (mean response time, throttle activity, curve error, standard deviation of lane position) 0.055 Yes
Morrow et al. 1990 Flight simulator (course performance, radio performance, summary score) 0.056 Yes
Horne & Baumber 1991 Driving simulator (mean following distance, standard deviation of mean following distance) 0.058 Yes
Colburn et al. 1993 Motorcycle simulator (leaving the roadway, total errors) 0.059 Yes
Flanagan et al. 1983 Driving (penalty points) 0.060 Yes
Louwerens et al. 1987 Driving (standard deviation of lane position, speed variability) 0.060 Yes
Horne & Baumber 1991 Driving simulator (mean following distance, standard deviation of mean following distance) 0.064 Yes
Rimm et al. 1982 Driving simulator (braking, steering) 0.064 Yes
McMillen et al. 1989 Driving simulator (lane changes, cars passed, time at maximum speed) 0.070 No
Ranney & Gawron 1986 Driving simulator (number of times over the speed limit) 0.070 Yes
Morrow et al. 1993 Flight simulator (severe altitude errors, summary score) 0.071 Yes
Taylor et al. 1994 Flight simulator (traffic avoidance, cockpit monitoring, landing) 0.077 Yes
Smiley et al. 1987 Driving (speed on open road curves, peripheral stimuli detected, and standard deviation of velocity on runway curves) 0.080 Yes
Taylor et al. 1996 Flying simulator (summary scores) 0.080 Yes
Louwerens et al. 1987 Driving (standard deviation of lane position, speed variability) 0.085 Yes
Colburn et al. 1993 Motorcycle simulator (leaving the roadway, total errors) 0.088 Yes
Morrow et al. 1990 Flight simulator (course performance, radio performance, severe altitude errors, summary score) 0.098 Yes
Morrow et al. 1993 Flight simulator (severe altitude errors, summary score) 0.101 Yes
Yesavage et al. 1994 Flight simulator (composite score) 0.101 Yes
Gawron & Ranney 1988 Driving (curve lateral position, curve lateral position deviation, straight lateral position deviation, left road departure, right road departure, curve speed, curve speed deviation, straight speed deviation, time between same-side departures, time outside lane) 0.103 Yes
Gawron & Ranney 1988 Driving simulator (# of obstacles struck, lateral position, number of times over the speed limit, total heading error, total lateral position errors) 0.103 Yes
Mongrain 1989 Driving simulator 0.120 Yes
Ranney & Gawron 1986 Driving simulator (curve heading error, curve lateral position, fixed curve lateral position, number of obstacles struck, number of times over the speed limit) 0.120 Yes
Louwerens et al. 1987 Driving (standard deviation of lane position, speed variability) 0.122 Yes

Table A2
Summary of Test Results for Divided Attention

Author Year Experimental Task BAC Impairment
Roehrs et al 1994b Divided attention task 0.008 Yes
Roehrs et al 1994a Tracking and visual search 0.013 Yes
Millar et al. 1992 Primary tracking and secondary visual reaction time 0.014 Yes
Hindmarch et al 1992 Tracking and visual search 0.020 No
Landauer & Howat 1983 Tracking and peripheral visual search 0.021 Yes
Mattila et al. 1992 Tracking and secondary task 0.026 Yes
Millar et al. 1992 Primary tracking and secondary visual reaction time 0.030 Yes
Mills & Bisgrove 1983a Central and peripheral number monitoring 0.030 No
Mills & Bisgrove 1983b Central and peripheral number monitoring 0.030 Yes
Wilkinson 1995 Compensatory tracking and visual search task 0.030 Yes
Wilkinson et al. 1989 Compensatory tracking and visual search task 0.030 Yes
Himdmarch et al. 1991 Compensatory tracking and detection of visual stimuli 0.033 No
Roehrs et al. 1993 Divided attention task 0.035 No
Mills & Bisgrove 1983 Central and peripheral number monitoring 0.036 No
Finnigan et al. 1995 Primary tracking and visual secondary RT task 0.040 No
Krueger 1986 Compensatory tracking, number monitoring and visual perception 0.040 Yes
Mills & Bisgrove 1983 Central and peripheral number monitoring 0.041 No
Marks and MacAvoy 1989 Central and peripheral light monitoring 0.043 Yes
Mills & Bisgrove 1983 Central and peripheral number monitoring 0.047 No
Roehrs et al 1994a Tracking and visual search 0.049 Yes
Landauer & Howat 1983 Tracking and peripheral visual search 0.050 Yes
Lex et al. 1994 Compensatory tracking and visual search task 0.050 No
Mattila et al. 1992 Tracking and secondary task 0.050 Yes
Wilkinson 1995 Compensatory tracking and visual search task 0.050 Yes
Hindmarch et al 1992 Tracking and visual search 0.052 No
Roehrs et al. 1989 Divided attention task 0.055 Yes
Finnigan et al. 1995 Primary tracking and visual secondary RT task 0.056 Yes
Lex et al. 1994 Compensatory tracking and visual search task 0.060 No
Millar et al. 1992 Primary tracking and secondary visual reaction time 0.060 Yes
Mills & Bisgrove 1983 Central and peripheral number monitoring 0.062 Yes
Finnigan et al. 1995 Primary tracking and visual secondary RT task 0.063 Yes
Himdmarch et al. 1991 Compensatory tracking and detection of visual stimuli 0.066 No
Maylor et al. 1990 Tracking and auditory detection 0.068 Yes
Lex et al. 1994 Compensatory tracking and visual search task 0.070 No
Wilkinson & Moskowitz 1989 Compensatory tracking and visual search task 0.070 Yes
Landauer & Howat 1983 Tracking and peripheral visual search 0.073 Yes
Finnigan et al. 1995 Primary tracking and visual secondary RT task 0.075 Yes
Lex et al. 1994 Compensatory tracking and visual search task 0.075 No
Mattila et al. 1992 Tracking and secondary task 0.076 Yes
Hindmarch et al 1992 Tracking and visual search 0.078 Yes
Krueger 1986 Compensatory tracking, number monitoring and visual perception 0.080 Yes
Lex et al. 1994 Compensatory tracking and visual search task 0.080 Yes
Wilkinson 1995 Compensatory tracking and visual search task 0.080 Yes
Mills & Bisgrove 1983 Central and peripheral number monitoring 0.089 Yes
Marks and MacAvoy 1989 Central and peripheral light monitoring 0.093 Yes
Mills & Bisgrove 1983 Central and peripheral number monitoring 0.095 Yes
Hindmarch et al 1992 Tracking and visual search 0.100 Yes
Mills & Bisgrove 1983 Central and peripheral number monitoring 0.100 Yes
Himdmarch et al. 1991 Compensatory tracking and detection of visual stimuli 0.104 Yes
Mills & Bisgrove 1983 Central and peripheral number monitoring 0.106 Yes
Krueger 1986 Compensatory tracking, number monitoring and visual perception 0.120 Yes
Himdmarch et al. 1991 Compensatory tracking and detection of visual stimuli 0.142 Yes

Table A 3
Summary of Test Results for Drowsiness

Author Year Experimental Task BAC Impairment
Roehrs et al 1994b Multiple sleep latency test 0.010 Yes
Roehrs et al 1994a Multiple sleep latency test 0.013 Yes
Roehrs et al. 1989 Multiple sleep latency test 0.020 Yes
Papineau et al. 1998 Multiple sleep latency test 0.021 No
Walsh et al. 1991 Multiple sleep latency test 0.034 Yes
Walsh et al. 1991 Repeated test of sustained Wakefulness 0.034 No
Roehrs et al. 1993 Multiple sleep latency test 0.035 Yes
Roehrs et al 1994b Multiple sleep latency test 0.040 Yes
Roehrs et al 1994a Multiple sleep latency test 0.049 Yes
Roehrs et al. 1989 Multiple sleep latency test 0.050 Yes
Papineau et al. 1998 Multiple sleep latency test 0.055 Yes
Roehrs et al 1994b Multiple sleep latency test 0.060 Yes
Roehrs et al. 1989 Multiple sleep latency test 0.060 Yes

Table A4
Summary of Test Results for Vigilance
Author Year Experimental Task Domain BAC Impairment
Gustafson 1986 Auditory RT in a Sustained attention setting Vigilance 0.021 No
Gustafson 1986 Visual RT in a Sustained attention setting Vigilance 0.028 No
Rohrbaugh et al. 1987 Sustained attention Vigilance 0.030 Yes
Rohrbaugh et al. 1988 Sustained attention Vigilance 0.030 Yes
Wilkinson 1995 Sustained attention Vigilance 0.030 Yes
Wilkinson & Moskowitz 1989 Sustained attention Vigilance 0.030 Yes
Horne & Gibbons 1991 Auditory Sustained attention Vigilance 0.034 Yes
Vermeeren & O'Hanlon 1998 Sustained attention Vigilance 0.045 Yes
Jansen et al. 1985 Sustained attention Vigilance 0.054 Yes
Gustafson 1986 Visual RT in a Sustained attention setting Vigilance 0.059 Yes
Rohrbaugh et al. 1988 Sustained attention Vigilance 0.063 Yes
Rohrbaugh et al. 1987 Sustained attention Vigilance 0.065 Yes
Horne & Gibbons 1991 Auditory Sustained attention Vigilance 0.066 Yes
Wilkinson & Moskowitz 1989 Sustained attention Vigilance 0.070 Yes
Wilkinson 1995 Sustained attention Vigilance 0.080 Yes
Rohrbaugh et al. 1988 Sustained attention Vigilance 0.086 Yes
Gustafson 1986 Auditory RT in a Sustained attention setting Vigilance 0.088 Yes
Rohrbaugh et al. 1987 Sustained attention Vigilance 0.090 Yes

Table A5
Summary of Test Results for Tracking
Author Year Experimental Task BAC Impairment
Mangold at al. 1996 Pursuit tracking 0.011 No
Mangold at al. 1996 Pursuit tracking 0.014 No
Cohen at al. 1987 Adaptive tracking 0.018 Yes
Hindmarch et al 1992 Tracking 0.020 No
Kuitunen et al. 1990 Tracking error severity index 0.021 No
Wilkinson & Moskowitz 1989 Critical tracking 0.030 Yes
Mangold at al. 1996 Pursuit tracking 0.036 No
van Steveninck et al. 1993 Adaptive tracking 0.038 No
Kuitunen et al. 1990 Tracking error severity index 0.040 No
Cohen at al. 1987 Adaptive tracking 0.043 No
Mangold at al. 1996 Pursuit tracking 0.043 No
Cohen at al. 1987 Adaptive tracking 0.044 Yes
Vermeeren & O'Hanlon 1998 Critical tracking 0.045 Yes
Hindmarch et al 1992 Tracking 0.052 No
Fillmore & Vogel-Sprott 1994 Pursuit Rotor Task 0.054 Yes
Fillmore & Vogel-Sprott 1995 Pursuit Rotor Task 0.058 Yes
Kuitunen et al. 1990 Tracking error severity index 0.060 Yes
Maylor et al. 1990 Pursuit tracking 0.068 No
Wilkinson & Moskowitz 1989 Critical tracking 0.070 Yes
Collins et al 1987 Compensatory tracking 0.077 Yes
Hindmarch et al 1992 Tracking 0.078 No
Kuitunen et al. 1990 Tracking error severity index 0.079 Yes
Hindmarch et al 1992 Tracking 0.100 Yes

Table A6
Summary of Test Results for Perception

Author Year Experimental Task BAC Impairment
Heishman et al. 1997 Time estimation 0.005 No
MacArthur et al/ 1982 Direction judgment 0.020 No
Heishman et al. 1997 Time estimation 0.025 No
Wang et al. 1992 Anticipation time 0.025 No
Gustafson 1986 Visual search task 0.027 No
Maylor et all. 1987 Visual search task 0.028 No
Post et al. 1996 Visual spatial attention 0.028 No
Wang et al. 1992 Anticipation time 0.030 No
Willumeit et al 1984 Audio-visual perception 0.032 No
Lapp et al. 1994 Time estimation 0.037 Yes
Mongrain 1989 Signal detection 0.040 Yes
Wang et al. 1992 Anticipation time 0.047 Yes
Willumeit et al 1984 Audio-visual perception 0.049 No
Deery & Love 1996 Traffic hazard perception 0.050 Yes
Wang et al. 1992 Anticipation time 0.050 No
Willumeit et al 1984 Audio-visual perception 0.050 No
Baker 1985 Pattern reproduction following short visual presentation 0.055 Yes
Wang et al. 1992 Anticipation time 0.055 No
Gustafson 1986 Visual search task 0.058 Yes
MacArthur et al. 1982 Direction judgment 0.060 No
Wang et al. 1992 Anticipation time 0.060 No
Wang et al. 1992 Anticipation time 0.065 No
Maylor et al. 1990 Auditory detection task 0.068 Yes
Wang et al. 1992 Anticipation time 0.070 No
Wang et al. 1992 Anticipation time 0.075 No
Lapp et al. 1994 Time estimation 0.078 Yes
Post et al. 1996 Visual spatial attention 0.078 Yes
Heishman et al. 1997 Time estimation 0.080 No
Mongrain 1989 Signal detection 0.080 Yes
Wang et al. 1992 Anticipation time 0.090 Yes
Wang et al. 1992 Anticipation time 0.095 Yes
Wang et al. 1992 Anticipation time 0.100 Yes
Mongrain 1989 Signal detection 0.120 Yes
Maylor et all. 1987 Visual search task 0.130 Yes
Mongrain 1989 Signal detection 0.160 Yes

Table A7
Summary of Test Results for Visual Functions

Author Year Experimental Task BAC Impairment
Nicholson et al. 1994 Contrast sensitivity 0.011 No
Cohen et al. 1987 Eye movements 0.018 No
Kuitunen et al. 1990 Coordination of extraocular muscles 0.021 No
Wang et al. 1992 Visual sensitivity, depth perception 0.025 No
Mattila et al. 1992 Coordination of extraocular muscles 0.026 Yes
Mattila et al. 1992 Nystagmus 0.026 No
Wang et al. 1992 Visual sensitivity, depth perception 0.030 No
Ross & Mughni 1995 Flight simulator (detection of angular acceleration) 0.037 Yes
van Steveninck et al. 1993 Smooth pursuit, saccadic peak velocity, saccadic latency, saccadic inaccuracy 0.038 Yes
Katoh 1988 Eye saccadic velocity 0.040 Yes
Kuitunen et al. 1990 Coordination of extraocular muscles 0.040 No
Cohen et al. 1987 Eye movements 0.043 Yes
Nicholson et al. 1994 Contrast sensitivity 0.043 Yes
Hogan & Gilmartin 1985 Amplitude of accomodation, tonic accomodation 0.045 No
Hogan & Gilmartin 1985 Heterophoria (6m), heterophoria (33cm), Accomodative-convergence/accomodation ratio, lateral fusional ability, near point of convergence 0.045 Yes
Wang et al. 1992 Depth perception 0.047 Yes
Wang et al. 1992 Visual sensitivity 0.047 No
Katoh 1988 Eye saccadic velocity 0.048 Yes
Barnes et al. 1985 Eye velocity 0.049 Yes
Mattila et al. 1992 Coordination of extraocular muscles 0.050 Yes
Mattila et al. 1992 Nystagmus 0.050 Yes
Pearson & Timney 1998 Contrast sensitivity 0.050 Yes
Wang et al. 1992 Depth perception 0.050 Yes
Wang et al. 1992 Visual sensitivity 0.050 No
Wang et al. 1992 Visual sensitivity, depth perception 0.050 No
Wang et al. 1992 Visual sensitivity, depth perception 0.055 No
Kuitunen et al. 1990 Coordination of extraocular muscles 0.060 No
Pearson & Timney 1998 Contrast sensitivity 0.060 Yes
Wang et al. 1992 Depth perception 0.060 Yes
Wang et al. 1992 Visual sensitivity 0.060 No
Hill & Toffolon 1990 Visual acuity, color vision, stereo vision 0.061 No
Hill & Toffolon 1990 Horizontal visual field, vertical visual field, accomodation, convergence 0.061 Yes
Wang et al. 1992 Depth perception 0.065 Yes
Wang et al. 1992 Visual sensitivity 0.065 No
Katoh 1988 Eye saccadic velocity 0.066 Yes
Reker 1988 Latency of isolated eye 0.066 No
Reker 1988 Velocity of isolated eye, coordinated head-eye movement 0.066 Yes
Hogan & Linfield 1983 Accomodative-convergence/accomodation ratio, near heterophoria, positive fusional ability, accomodation 0.067 No
Hogan & Linfield 1983 Negative fusional ability, distance heterophoria, near point of convergence 0.067 Yes
Pearson & Timney 1998 Contrast sensitivity 0.070 Yes
Wang et al. 1992 Depth perception 0.070 Yes
Wang et al. 1992 Visual sensitivity 0.070 No
Andre 1996 Contrast sensitivity 0.073 Yes
Barnes et al. 1985 Eye displacement gain, eye velocity, vestibulo-ocular response 0.073 Yes
Wang et al. 1992 Depth perception 0.075 Yes
Wang et al. 1992 Visual sensitivity 0.075 No
Leibowitz, et al. 1992 Contrast sensitivity 0.076 Yes
Mattila et al. 1992 Coordination of extraocular muscles 0.076 Yes
Mattila et al. 1992 Nystagmus 0.076 Yes
Barnes 1984 Visual pursuit, vestibular-ocular reflex suppression 0.077 Yes
Kuitunen et al. 1990 Coordination of extraocular muscles 0.079 No
Zulauf et al. 1988 Contrast sensitivity 0.080 Yes
Katoh 1988 Eye saccadic velocity 0.085 Yes
Andre 1994 Contrast sensitivity 0.088 Yes
Wang et al. 1992 Depth perception 0.090 Yes
Wang et al. 1992 Visual sensitivity 0.090 No
Wang et al. 1992 Depth perception 0.095 Yes
Wang et al. 1992 Visual sensitivity 0.095 No
Pearson & Timney 1998 Contrast sensitivity 0.100 Yes
Wang et al. 1992 Depth perception 0.100 Yes
Wang et al. 1992 Visual sensitivity 0.100 No
Reker 1988 Latency of isolated eye, velocity of isolated eye, coordinated head-eye movement 0.107 Yes
Hill & Toffolon 1990 Visual acuity, horizontal visual field, vertical visual field, color vision, stereo vision, accomodation, convergence 0.134 Yes

Table A8
Summary of Test Results for cognitive Tasks
Author Year Experimental Task BAC Impairment
Heisman 1997 Digit-symbol substitution 0.005 No
Heisman 1997 Number recognition 0.005 No
Heisman 1997 Word recall 0.005 No
Mangold et al. 1996 Digit-symbol substitution 0.011 No
Mangold et al. 1996 Digit-symbol substitution 0.014 No
Millar et al. 1992 Auditory short-term memory 0.014 No
Pickworth et al. 1997 Card sorting 0.014 No
Pickworth et al. 1997 Digit-symbol substitution 0.014 No
Pickworth et al. 1997 Letter search 0.014 No
Pickworth et al. 1997 Serial addition/subtraction 0.014 No
Millar et al. 1995 Recognition and memory task 0.016 Yes
Hindmarch et al 1992 Color test 0.020 No
Hindmarch et al 1992 Digit-symbol substitution 0.020 No
Hindmarch et al 1992 Letter recognition 0.020 No
Hindmarch et al 1992 Mental arithmetic 0.020 No
Hindmarch et al 1992 Spatial orientation 0.020 No
Hindmarch et al 1992 Sternberg 0.020 No
Hindmarch et al 1992 Sternberg 0.020 No
Kuitunen et al. 1990 Digit-symbol substitution 0.021 No
Kuitunen et al. 1990 Symbol copying 0.021 No
Heisman 1997 Digit-symbol substitution 0.025 No
Heisman 1997 Number recognition 0.025 Yes
Heisman 1997 Word recall 0.025 No
Mattila et al. 1992 Digit-symbol substitution 0.026 No
Hindmarch et al. 1991 Sternberg 0.027 No
Millar et al. 1992 Auditory short-term memory 0.030 No
Wilkinson 1995 Sternberg 0.030 No
Wilkinson 1995 Visual backward masking 0.030 Yes
Roehrs et al. 1993 Digit-symbol substitution 0.035 Yes
Mangold et al. 1996 Digit-symbol substitution 0.036 No
Pickworth et al. 1997 Card sorting 0.036 No
Pickworth et al. 1997 Digit-symbol substitution 0.036 No
Pickworth et al. 1997 Letter search 0.036 No
Pickworth et al. 1997 Serial addition/subtraction 0.036 No
Lamb & Robertson 1987 Pattern recognition 0.037 No
Doms et al. 1988 Cross-out groups of four dots 0.038 Yes
Doms et al. 1988 Cross-out letter configuration 0.038 No
Doms et al. 1988 Memory 0.038 Yes
Doms et al. 1988 Symbol marking 0.038 Yes
van Steveninck 1993 Digit-symbol substitution 0.038 No
Kuitunen et al. 1990 Digit-symbol substitution 0.040 No
Kuitunen et al. 1990 Symbol copying 0.040 No
Hasenfratz et al. 1993 Digit patterns recognition 0.042 Yes
Mangold et al. 1996 Digit-symbol substitution 0.043 No
Millar et al. 1995 Recognition and memory task 0.043 Yes
de Wit et al. 1987 Digit-symbol substitution 0.046 Yes
Ryan et al. 1996 Item recognition 0.048 Yes
Hartley & Coxon 1984 Reading comprehension 0.049 Yes
Lyvers & Maltzman 1991 Card sorting 0.049 Yes
Lukas et al. 1989 Digit-symbol substitution 0.050 No
Mattila et al. 1992 Digit-symbol substitution 0.050 Yes
Wilkinson 1995 Sternberg 0.050 No
Wilkinson 1995 Visual backward masking 0.050 Yes
Hindmarch et al 1992 Color test 0.052 No
Hindmarch et al 1992 Digit-symbol substitution 0.052 No
Hindmarch et al 1992 Letter recognition 0.052 No
Hindmarch et al 1992 Mental arithmetic 0.052 No
Hindmarch et al 1992 Spatial orientation 0.052 No
Hindmarch et al 1992 Sternberg 0.052 No
Hindmarch et al 1992 Sternberg 0.052 No
Baker 1985 Digit recall 0.055 No
Baker 1985 Velocity estimation 0.055 Yes
Lukas et al. 1989 Digit-symbol substitution 0.058 No
Gengo et al. 1990 Digit-symbol substitution 0.060 Yes
Kennedy et al 1993 Code substitution 0.060 Yes
Kennedy et al 1993 Grammatical reasoning 0.060 No
Kennedy et al 1993 Mathematical processing 0.060 Yes
Kennedy et al 1993 Pattern discrimination 0.060 Yes
Kennedy et al 1993 Spatial orientation 0.060 Yes
Kennedy et al 1993 Sternberg 0.060 Yes
Kuitunen et al. 1990 Digit-symbol substitution 0.060 Yes
Kuitunen et al. 1990 Symbol copying 0.060 No
Lex et al. 1988 Card rotation 0.060 No
Lex et al. 1988 Sentence completion 0.060 No
Lex et al. 1988 Identification of repetitions of sample digits 0.060 Yes
Millar et al. 1992 Auditory short-term memory 0.060 No
Lamb & Robertson 1987 Pattern recognition 0.061 Yes
Lukas et al. 1989 Digit-symbol substitution 0.062 No
Pickworth et al. 1997 Card sorting 0.062 No
Pickworth et al. 1997 Digit-symbol substitution 0.062 No
Pickworth et al. 1997 Letter search 0.062 No
Pickworth et al. 1997 Serial addition/subtraction 0.062 No
Maylor et al. 1990 Recall 0.064 Yes
Maylor et al. 1990 Reading 0.064 Yes
Fillmore et al. 1998 Digit patterns recognition 0.066 Yes
Hindmarch et al. 1991 Sternberg 0.066 No
Maylor et al. 1989 Letter recognition 0.069 Yes
Lukas et al. 1989 Digit-symbol substitution 0.070 Yes
Lukas et al. 1989 Digit-symbol substitution 0.075 Yes
Mattila et al. 1992 Digit-symbol substitution 0.076 Yes
Ryan et al. 1996 Item recognition 0.076 Yes
Collins et al 1987 Mental arithmetic 0.077 No
Collins et al 1987 Pattern recognition 0.077 Yes
Collins et al 1987 Problem solving 0.077 No
Fillmore & Vogel-Sprott 1997 Number patterns recognition 0.077 Yes
Hindmarch et al 1992 Color test 0.078 No
Hindmarch et al 1992 Digit-symbol substitution 0.078 Yes
Hindmarch et al 1992 Letter recognition 0.078 No
Hindmarch et al 1992 Mental arithmetic 0.078 No
Hindmarch et al 1992 Spatial orientation 0.078 No
Hindmarch et al 1992 Sternberg 0.078 No
Hindmarch et al 1992 Sternberg 0.078 No
Kuitunen et al. 1990 Digit-symbol substitution 0.079 Yes
Kuitunen et al. 1990 Symbol copying 0.079 Yes
Nelson et al. 1986 Recall, judgment, and recognition 0.079 Yes
Oborne & Rogers 1983 Sternberg 0.079 Yes
Heisman 1997 Digit-symbol substitution 0.080 Yes
Heisman 1997 Number recognition 0.080 Yes
Heisman 1997 Word recall 0.080 Yes
Lukas et al. 1989 Digit-symbol substitution 0.080 No
Wilkinson 1995 Sternberg 0.080 No
Wilkinson 1995 Visual backward masking 0.080 Yes
Pickworth et al. 1997 Card sorting 0.096 Yes
Pickworth et al. 1997 Digit-symbol substitution 0.096 No
Pickworth et al. 1997 Letter search 0.096 No
Pickworth et al. 1997 Serial addition/subtraction 0.096 Yes
Hindmarch et al 1992 Color test 0.100 No
Hindmarch et al 1992 Digit-symbol substitution 0.100 Yes
Hindmarch et al 1992 Letter recognition 0.100 No
Hindmarch et al 1992 Mental arithmetic 0.100 No
Hindmarch et al 1992 Spatial orientation 0.100 No
Hindmarch et al 1992 Sternberg 0.100 No
Hindmarch et al 1992 Sternberg 0.100 No
Hindmarch et al. 1991 Sternberg 0.104 No
Kennedy et al 1993 Code substitution 0.110 Yes
Kennedy et al 1993 Grammatical reasoning 0.110 No
Kennedy et al 1993 Mathematical processing 0.110 Yes
Kennedy et al 1993 Pattern discrimination 0.110 Yes
Kennedy et al 1993 Spatial orientation 0.110 Yes
Kennedy et al 1993 Sternberg 0.110 Yes
Pickworth et al. 1997 Card sorting 0.117 Yes
Pickworth et al. 1997 Digit-symbol substitution 0.117 Yes
Pickworth et al. 1997 Letter search 0.117 No
Pickworth et al. 1997 Serial addition/subtraction 0.117 Yes
Pickworth et al. 1997 Card sorting 0.139 Yes
Pickworth et al. 1997 Digit-symbol substitution 0.139 Yes
Pickworth et al. 1997 Letter search 0.139 No
Pickworth et al. 1997 Serial addition/subtraction 0.139 Yes
Hindmarch et al. 1991 Sternberg 0.142 Yes
Kennedy et al 1993 Code substitution 0.160 Yes
Kennedy et al 1993 Grammatical reasoning 0.160 No
Kennedy et al 1993 Mathematical processing 0.160 Yes
Kennedy et al 1993 Pattern discrimination 0.160 Yes
Kennedy et al 1993 Spatial orientation 0.160 Yes
Kennedy et al 1993 Sternberg 0.160 Yes

Table A9
Summary of Test Results for Psychomotor Skills
Author Year Experimental Task BAC Impairment
Mangold et al. 1996 Body balance 0.011 No
Mangold et al. 1996 Body balance 0.014 No
Pickworth et al. 1997 Circular lights 0.014 Yes
Perrine 1994 Diving 0.017 No
Cohen et al. 1987 Body balance 0.018 Yes
Kuitunen et al. 1990 Body balance 0.021 No
Mattila et al. 1992 Body balance 0.026 No
Price & Flax 1982 Drill press operation 0.028 No
Mills & Bisgrove 1983 Body sway 0.030 Yes
Mangold et al. 1996 Body balance 0.036 No
Pickworth et al. 1997 Circular lights 0.036 Yes
van Steveninck et al. 1993 Body balance 0.038 No
Kuitunen et al. 1990 Body balance 0.040 No
Mongrain 1989 Simulated raquetball 0.040 No
Perrine 1994 Diving 0.040 Yes
Schuckit 1985 Body sway 0.040 Yes
Cohen et al. 1987 Body balance 0.043 No
Mangold et al. 1996 Body balance 0.043 Yes
Cohen et al. 1987 Body balance 0.044 Yes
Price et al. 1986 Electronics assembly task 0.049 Yes
Lukas et al. 1989 Body sway 0.050 Yes
Lukas et al. 1989 Finger tapping, hand steadiness 0.050 No
Mattila et al. 1992 Body balance 0.050 No
Tianwo et al. 1995 Body balance 0.053 Yes
Lukas et al. 1989 Finger tapping, hand steadiness, body sway 0.058 No
Kennedy et al 1993 Finger tapping 0.060 Yes
Kuitunen et al. 1990 Body balance 0.060 No
Maylor & Rabbitt 1987 Video game 0.061 Yes
Lukas et al. 1989 Body sway 0.062 Yes
Lukas et al. 1989 Finger tapping, hand steadiness 0.062 No
Mills & Bisgrove 1983 Body sway 0.062 Yes
Pickworth et al. 1997 Circular lights 0.062 Yes
Price & Flax 1982 Drill press operation 0.062 Yes
Price et al. 1986 Electronics assembly task 0.069 Yes
Lukas et al. 1989 Body sway 0.070 Yes
Lukas et al. 1989 Finger tapping, hand steadiness 0.070 No
Perrine 1994 Diving 0.071 Yes
Laberg & Löberg 1989 Hand steadiness and coordination 0.073 Yes
Lukas et al. 1989 Body sway 0.075 No
Lukas et al. 1989 Finger tapping, hand steadiness 0.075 No
Mattila et al. 1992 Body balance 0.076 Yes
Azcona et al. 1995 Finger tapping 0.078 No
Kuitunen et al. 1990 Body balance 0.079 No
Lukas et al. 1989 Body sway 0.080 Yes
Lukas et al. 1989 Finger tapping, hand steadiness 0.080 No
Schuckit 1985 Body sway 0.081 Yes
Price & Flax 1982 Drill press operation 0.092 Yes
Price et al. 1986 Electronics assembly task 0.093 Yes
Pickworth et al. 1997 Circular lights 0.096 Yes
Perrine 1994 Diving 0.097 No
Perrine 1994 Diving 0.100 Yes
Kennedy et al 1993 Finger tapping 0.110 Yes
Pickworth et al 1997 Circular lights 0.117 Yes
Mongrain 1989 Simulated raquetball 0.120 No
Perrine 1994 Diving 0.123 Yes
Pickworth et al 1997 Circular lights 0.139 Yes
Kennedy et al 1993 Finger tapping 0.160 Yes

Table A10
Summary of Test Results for Choice RT
Author Year Experimental Task BAC Impairment
Millar et al. 1992 RT to 1 of 5 circles 0.014 No
Hindmarch et al 1992 Report wich of 6 lights turned on and off 0.020 No
MacArthur & Sekuler 1982 Choice RT 0.020 No
MacArthur & Sekuler 1982 Choice RT 0.020 Yes
Hindmarch et al. 1991 Estinguish 1 of 6 lights 0.027 No
Maylor et all. 1987 Choice RT to video characters 0.029 No
Jääskeläinen et al. 1995 RT to auditory stimuli 0.030 No
Millar et al. 1992 RT to 1 or 5 circles 0.030 No
Colrain at al. 1993 RT to presence of vertical check pattern 0.032 Yes
Finnigan et al. 1995 Report changes in 1 of 5 circles 0.040 No
Gengo et al. 1990 Report wich of 6 lights turned on and off 0.040 Yes
Colrain at al. 1993 RT to presence of vertical check pattern 0.043 Yes
Antebi 1982 Choice RT 0.045 Yes
Vermeeren & O'Hanlon 1998 Choice RT with distracting cues 0.045 Yes
Hindmarch et al 1992 Report wich of 6 lights turned on and off 0.052 No
Finnigan et al. 1995 Report changes in 1 of 5 circles 0.056 No
Jääskeläinen et al. 1995 RT to auditory stimuli 0.060 No
Kennedy et al 1993 Four-choice RT 0.060 Yes
MacArthur & Sekuler 1982 Choice RT 0.060 No
MacArthur & Sekuler 1982 Choice RT 0.060 Yes
Millar et al. 1992 RT to 1 or 5 circles 0.060 No
Jääskeläinen et al. 1996 Choice RT with auditory distraction 0.062 Yes
Finnigan et al. 1995 Report changes in 1 of 5 circles 0.063 No
Hindmarch et al. 1991 Estinguish 1 of 6 lights 0.066 Yes
Maylor et al. 1992 2-, 4-, or 8-choice RT 0.067 Yes
Colrain at al. 1993 RT to presence of vertical check pattern 0.068 Yes
Mulvihill et al. 1996 Choice RT with inhibitory control 0.073 Yes
Finnigan et al. 1995 Report changes in 1 of 5 circles 0.075 Yes
Collins et al 1987 RT to onset of one of 5 lights 0.077 Yes
Hindmarch et al 1992 Report wich of 6 lights turned on and off 0.078 Yes
Colrain at al. 1993 RT to presence of vertical check pattern 0.096 Yes
Hindmarch et al 1992 Report wich of 6 lights turned on and off 0.100 Yes
Hindmarch et al. 1991 Estinguish 1 of 6 lights 0.104 Yes
Kennedy et al 1993 Four-choice RT 0.110 Yes
Maylor et all. 1987 RT to video characters 0.130 Yes
Hindmarch et al. 1991 Estinguish 1 of 6 lights 0.142 Yes
Kennedy et al 1993 Four-choice RT 0.160 Yes

Table A11
Summary of Test Results for Simple RT
Author Year Experimental Task BAC Impairment
Heishman et al. 1997 Simple RT 0.005 No
Cohen et al. 1987 Respond to onset of visual clock 0.018 No
Heishman et al. 1997 Simple RT 0.025 No
Wang et al. 1992 Respond to light onset 0.025 No
Wang et al. 1992 Respond to light onset 0.030 No
Cohen et al. 1987 Respond to onset of visual clock 0.043 Yes
Cohen et al. 1987 Respond to onset of visual clock 0.044 Yes
Wang et al. 1992 Respond to light onset 0.047 Yes
Wang et al. 1992 Respond to light onset 0.050 No
Baker 1985 RT to auditory or visual stimulus 0.055 Yes
Wang et al. 1992 Respond to light onset 0.055 No
Wang et al. 1992 Respond to light onset 0.060 Yes
Wang et al. 1992 Respond to light onset 0.065 No
Wang et al. 1992 Respond to light onset 0.070 No
Wang et al. 1992 Respond to light onset 0.075 Yes
Azcona et al 1995 Respond to single stimulus onset 0.078 Yes
Heishman et al. 1997 Simple RT 0.080 No
Wang et al. 1992 Respond to light onset 0.090 No
Wang et al. 1992 Respond to light onset 0.095 No
Wang et al. 1992 Respond to light onset 0.100 Yes

Table A12
Summary of Test Results fof CFF
Author Year Experimental Task BAC Impairment
Millar et al. 1992 Critical flicker fusion 0.014 No
Hindmarch et al 1992 Critical flicker fusion 0.020 No
Kuitunen et al. 1990 Critical flicker fusion 0.021 No
Hindmarch 1991 Critical flicker fusion 0.027 No
Millar et al. 1992 Critical flicker fusion 0.030 No
Kuitunen et al. 1990 Critical flicker fusion 0.040 No
Hindmarch et al 1992 Critical flicker fusion 0.052 No
Jansen et al. 1985 Critical flicker fusion 0.054 No
Baker 1985 Critical flicker fusion 0.055 No
Kuitunen et al. 1990 Critical flicker fusion 0.060 No
Millar et al. 1992 Critical flicker fusion 0.060 No
Hindmarch 1991 Critical flicker fusion 0.066 No
Azcona et al. 1995 Critical flicker fusion 0.078 No
Hindmarch et al 1992 Critical flicker fusion 0.078 No
Kuitunen et al. 1990 Critical flicker fusion 0.079 No
Hindmarch et al 1992 Critical flicker fusion 0.100 Yes
Hindmarch 1991 Critical flicker fusion 0.104 Yes
Hindmarch 1991 Critical flicker fusion 0.142 Yes

Table A13
Summary of Test Results for Aftereffects

Author Year Experimental Task BAC Impairment
Cohen at al. 1987 Adaptive tracking 0.000 No
Cohen et al. 1987 Body balance 0.000 No
Cohen et al. 1987 Eye movements 0.000 No
Cohen et al. 1987 Simple visual RT 0.000 No
Kennedy et al 1993 Delta 0.000 No
Kuitunen et al. 1990 Body balance 0.000 No
Kuitunen et al. 1990 Coordination of extraocular muscles 0.000 No
Kuitunen et al. 1990 Critical flicker fusion 0.000 No
Kuitunen et al. 1990 Digit-symbol substitution 0.000 No
Kuitunen et al. 1990 Symbol copying 0.000 No
Kuitunen et al. 1990 Tracking error severity index 0.000 No
Morrow et al. 1990 Flight simulator (severe altitude errors, summary score) 0.000 No
Pickworth et al. 1997 Card sorting 0.000 No
Pickworth et al. 1997 Circular lights 0.000 No
Pickworth et al. 1997 Digit-symbol substitution 0.000 No
Pickworth et al. 1997 Letter search 0.000 No
Pickworth et al. 1997 Serial addition/subtraction 0.000 No
Roehrs et al 1994b Divided attention task 0.000 No
Roehrs et al 1994b MSLT 0.000 Yes
Roehrs et al. 1989 MSLT 0.000 Yes
Ross & Mughni 1995 Detection of angular motion 0.000 Yes
Taylor et al. 1994 Flight simulator 0.000 Yes
Taylor et al. 1996 Flight simulator 0.000 No
Yesavage et al. 1986 Flight simulator 0.000 Yes
Yesavage et al. 1994 Flight simulator 0.000 Yes