Investigation of alcoholic hang-over effects on driving performance

Statens väg- och trafikinstitut (VTI) - 58101 Linköping

Swedish Road and Traffic Research Institute ■ S-581 01 Linköping Sweden

Investigation of alcoholic hang-over

effects on driving performance

by Hans Laurell and Jan Törnros

Reprint from Blutalkohol Vol. 20/1983 p. 489-499 Nr 98.1984

N a tio n a l S w edish R o a d a n d Traffic R esearch Institute S-581 01 L in k ö p in g / S w ed en

Ha n s La u r e l l a n d Ja n Tö r n r o s

Investigation of alcoholic hang-over effects

on driving performance

Untersuchungen zur Fahrtiichtigkeit

in der post-alkoholischen Phase

1 Introduction

Studies of laboratory tasks as well as of car driving have shown that alcohol can impair performance even after doses, resulting in blood alcohol concentrations (BAC) of less than 50 mg%. Thus, in an investigation of alcohol related perform ­ ance decrement in critical driving situations, significant impairment was recorded at BACs averaging 42 mg% (Laurell, 1977).

It is also a m atter of everyday experience that aftereffects of drinking may remain long after all alcohol has been metabolized.

The after- or post-toxic or hang-over effects have not been subjected to wide- ranging study. This holds true even more when it comes to hang-over effects on driver performance.

L a b o r a to r y s t u d ie s h a v e d e m o n s tr a te d d e c r e a s e d p e r fo r m a n c e in c e r ta in i n t e l ­ le c t u a l fu n c t io n s . T h is is a ls o tr u e o f p e r c e p tu a l a b ilit ie s , h a n d s t e a d in e s s , c o o r d i­ n a t i o n , e t c . (TAKALAet a l ., 1958; Go l d b e r g, 1966; Ke l l ye t a l., 1970; MYRSTENet a l . ,

1970; G o L D e t a l ., 1973; SEPPÄLÄet a l ., 1976; MYRSTENet a l., 1980; TiCHAUERet a l .) .

Driving simulator studies have also indicated that the after effects of alcohol exert a certain detrim ental influence on driving performance (St e n in g and

Du r e m a n, 1974).

However, we have been unable to find any investigations into possible effects of hang-over on driver performance in traffic or in closed-course driving.

The duration of the alcoholic hang-over effects, has only been studied in connection with laboratory tasks. Decreased performance has been noted by Go l d

et al. (1973) up to 18 hours beyond the alcoholic peak. They also observed that the higher the peak, the more pronounced the impairment in the post-toxic state.

Se p p ä l äet ah (1976) suggest that the most detrimental effects could occur as late as

24 hours after drinking.

2 M ethods

2.1 Subjects

Subjects: 6 women and 16 men, aged 19—38 acted as paid volunteer subjects. Not until our subjects had actually volunteered for “a car driving experim ent” were they informed about the fact that the investigation also included ölcohol and

were again asked if they wanted to participate. All subjects acted as their own controls. They were all healthy, using no medication or drugs.

A num ber of studies have reported difficulties in inducing hang-over under the usual laboratory circumstances (e. g. Bo n t e, Vo l c k, 1978). Therefore in this study,

special emphasis was placed on the attempt to reproduce the circumstances under which hang-over in non-alcoholics appears in our culture. To enhance that aim the subjects were chosen so that the five of them, taking part each Friday, already knew each other.

2.2 Driving task

The driving task was largely the same as was used in earlier studies of effects of alcohol on driving performance ( La u r e l l, 1977).

Upon a signal, the driver had to carry out on avoidance maneuvre and, in doing this, try to avoid knocking over pylon cones which were placed along the avoidance path. The tolerance on either side of the car was approximately 15 centimeters. The number of cones, knocked over, was employed as a measure of driver performance.

The signal could be presented at either one of four positions in the cone setting (see figure 1) and if presented above the left headlight position, simulated and obstacle in front of and to the left of the car, and thus required an avoidance maneuvre to the right and vice versa. The order of presentation of positions was randomized for each subject and each treatm ent condition. In each session, the course was negotiated 10 times by each subject - one per signal alternative plus two randomized. In addition, two “blind” trials, in which no avoidance stimulus was presented, were inserted at random among the rest. Two warm-up trials preceded each session.

2.3 Vehicle and presentation of stimulus signal

The experimental vehicle was a 1967 Volvo Station Wagon. For presentation of the avoidance signal, the car had been equipped with a photocell-system, the light of which was reflected via a reflector placed inconspicuously among the cones. The photocell triggered a relay, cutting the power of one of two electro magnets and thus releasing a spring-loaded arm which served as the stimulus. This way, the experim enter could not influence the timing of the signal. The photocell relay also triggered a counter which was stopped by the contact for the brake lights, thus providing a measure of the driver’s brake reaction time. Vehicle speed was controlled via a hand throttle device by the experimenter.

2.4 Motivation

In order to keep motivation at a high level throughout the investigation, the amount of payment was made dependent upon performance. For each trial the driver had at his disposal a sum of 25 SEK. This sum of money was reduced for each cone, knocked over. A cone in one of the outer rows rendered a 2 SEK reduction and in the inner rows a 3 SEK reduction. Cones hit prior to the stimulus signal cost 1 SEK. Reductions were maximized to 20 SEK. This sum also rep­ resented the punishment for having swerved into the wrong lane or performing no evasive maneuvre at all when an avoidance maneuvre was called for.

2.5 Procedure

A couple of days prior to the experimental sessions, all subjects practised the driving task until they reached a stable level of performance. Reaching this level required some 2.5 hours of driving.

Half of the subjects returned for two experimental sessions in the normal condition (N) a couple of days prior to the “night of the party” . The other half took their corresponding tests a couple of days after the hang-over. In^the normal

condition, the first m easurem ents (N l) were carried out at around nine o’clock and the second ones (N2) three hours later.

Five subjects participated in each drinking party, during which, free and ample supply of food and alcoholic beverages (beer, wine and distilled) was provided. The parties lasted between 6 p. m. and midnight. There were neither any restrictions nor any requirem ents as to eating and drinking — all subjects ate and drank at their own discretion. All subjects stayed overnight at the research institute supervised by the experimenters.

Eight hours after going to sleep, the subjects were awakened and breath alcohol tests were taken. The BACs were then monitored by frequent measurements, with the frequency of m easurements increasing to every 5—10 minutes as zero BAC was neared. A t the point when no alcohol could be detected by breath analysis, the first performance measurements in the hang-over state (H I) were carried out.

Immediately prior to all driving tests, the subjects gave subjective ratings on a five-point scale as to the severity of their hang-over and on each of twelve variables related to recognized hang-over effects (see table 3).

Three hours later, the second hang-over measurements (H2) were obtained.

S N o . O rder o f p resen tation N l N 2 H I H 2 1 j. N -H 137 135 111 148 2 9 N -H 92 97 90 92 3 H -N 158 168 98 157 4 H -N 111 155 118 80 5 N -H 188 148 130 129 6 9 H -N 149 160 136 120 7 9 H -N 130 117 111 69 8 N -H 137 171 137 147 9 N -H 140 112 81 93 10 H -N 138 129 107 130 11 N -H 133 126 108 115 12 N -H 133 112 106 101 13 H -N 123 139 82 93 1 4 9 H -N 74 63 56 72 1 5 9 N -H 147 154 77 98 16 N -H 139 160 123 112 17 H -N 151 184 120 144 1 8 9 H -N 108 77 97 70 19 H -N 161 144 82 128 20 H -N 134 123 112 105 21 . N -H 150 165 160 121 22 N -H 137 141 102 94 X 134 135 107 110 M d 137. 140 108 109 P25 ’ 123 117 90 93 P75 149 160 120 • 129 s 24 30 23 26

2.7 BAC m easurem ents

Blood alcohol concentrations were measured during the six hours of alcohol consumption as well as in the following morning. The intention was to obtain BAC measures on each subject at one hour intervals. However, due to difficulties in preventing subjects from drinking during the 15 minute period necessary for reliable BAC m easurem ent, this schedule could not be maintained. The m easure­ ments were carried out by breath sampling with two Alcolmeters (Lion Laboratories LTD). These instruments were calibrated against calibration air ampoules containing 50 mg% alcohol. Calibrations were made prior to each sampling.

3 Results

3.1 Performance m easurements

Table 1 shows that the performance scores in the two hang-over sessions, when combined, (H l + H2) were lower than the performance in the normal sessions for all 22 subjects. This is presented graphically in figure 2, where a comparison is made between hang-over and normal performance. None of the subjects reaches the normal perform ance level i. e. 100 %. In comparison with the normal perform ­ ance, the over all m ean as well as the median indicate a 19 % impairment.

The difference in performance between normal and hang-over conditions is statistically significant (p < 0.005, Wilcoxon).

Figure 2 D rivin g p erform ance during h ang-over (at zero B A C + at three hrs later). P erform an ce exp ressed as per cen t o f norm al perform ance

The two normal sessions are not significantly different (p < 0.05, Wilcoxon), implying that learning effects are unlikely to have influenced the results. A comparison between the first sessions in normal- and hang-over conditions (N l, H I) reveals that 19 out of 22 drivers scored worse in the first hang-over than in the first of the normal conditions. The average performance decrement was 20 % and the median 19 % (see figure 3). The difference between conditions is signifi­ cant (p < 0.005, Wilcoxon).

Figure 3 D rivin g perform ance during h ang-over (at zero B A C ). P erform an ce ex p ressed as per cent o f norm al perform ance

The comparison between N2 and H2, three hours later, produces almost the same picture (see figure 4). The difference between conditions is significant (p < 0.005, Wilcoxon). There is a weak tendency towards a smaller performance decrement at H2 than at H I. However, there is no significant difference between N l and N2, or between H I and H2 (p < 0.05, Wilcoxon).

If the concept of “negative score” is omitted, leaving any changes in performance to be expressed as number of cones knocked over, all comparisons still show significant differences (N — H , p < 0.005; N l - H I, p < 0.005; N2 - H2, p < 0.005; Wilcoxon).

There were a total of five false actions; one occurred in H I and four in H2. There was no false action in the normal conditions.

3.3 BAC

The average for all subjects’ highest recorded BAC readings between 6 p. m. and midnight, was 147 mg% and at 8 a. m. the next day, 46 mg%.

% of each subject's normal performance

F igure 4 D riving perform ance during h an g-over (at three hrs after reaching zero B A C ). P erform an ce ex p ressed as per cen t o f norm al

3.4 Hang-over

The overall ratings by the 22 subjects of the severity of their hang-over at H I (when their BAC first reaches zero) and at H2 (three hours after zero BAC) are presented in figure 5. No. o f subjects

15

10

3

4

F igure 5 T h e num ber o f su b jects w h o se lf-estim a ted their hang-over at each o f five lev els o f sev erity (N = 22)

An analysis of the overall rating of hang-over severity showed it not to be significantly related to driving performance.

There was a non-significant correlation between subjective hang-over and BAC at wake-up (rSpeannan rank = 0-16; t = 0.72; df = 20; p > 0.10).

As for background variables, there were neither gender (p > 0.05, Mann- W hitney U-test) nor age related differences in performance decrement (rSpeanilan rank = 0.33; t = 1.56; df = 20; p > 0.05). The lack of statistical significance also holds true for the correlation between the subjects’ normal alcohol consumption and performance decrement (rSpearman rank = 0.17; t = 0.77; df = 20; p > 0.10).

4 Discussion

The results give clear evidence of the performance degrading effects of alcoholic hang-over although all alcohol has been metabolized, following alcohol consump­ tion to the approximate level of 150 mg%. Further, it can be concluded that the degrading effects prevail for at least three hours after all alcohol has been metabolized.

Earlier results, primarily derived from psychomotor testing, support the existing data from actual car driving. When these results are compared with the earlier ones, they are strikingly clear and unambiguous.

The fact that behavioural effects were observed three hours after all alcohol had been metabolized (corresponding to 15 hours after peak BAC) does not mean that three hours constitutes a farther limit for performance degradations. Other studies have found effects even after more than 15 hours ( Tic h a u e r et al., 1971; Go l d

e t al., 1973; SEPPÄLÄet al., 1976).

Se p p ä l ä e t al. (1976) carried out psycho-motor testing from 12 to 16 hours after

drinking — the point at which they considered hang-over to be at its worst, and found performance impairment.

Tic h a u e ret al. (1971) found effects at even greater time distances. When B ACs

had exceeded 120 mg% , after-effects could be observed at 18 to 20 hours after peak BAC. Thus, there are reasons for further studies of after-effect duration.

The present results do not demonstrate any significant correlations between performance degradation and subjective hang-over symptoms. However, there was a tendency towards greater impairment of performance with higher degrees of hang-over. These results are in accordance with Se p p ä l ä et al. (1976) who also

found that performance did not correlate with subjective hang-over.

No hang-over symptoms at all or just slight were reported by 12 subjects at the point when all alcohol had been metabolized (H I). Thus, the fact that no significant correlations could be found may be attributed to the reduced variation in the subjective rating of hang-over. A nother possible explanation could be that the driving skills that were affected are less vulnerable to such physiological changes as are manifested in subjective discomfort than to changes among other underlying factors, not producing discomfort.

It is also pointed out by Se p p ä l äet al. that the basic mechanisms involved in the

indicate that the changes in psycho-motor performance are not necessarily related to the abnormal physiological conditions prevailing during hang-over.

In spite of the fact that so few hang-over symptoms were reported, everyone of the 22 drivers scored worse in the driving task the day after alcohol consumption than they did in their normal performance. This indicates that, irrespective of subjective well-being, it is difficult to assess one’s own fitness to drive. This conclusion is based on the presumption of an alcohol consumption corresponding to peak BACs of 115—180 mg%. However, it is not improbable that lower BACs should also cause performance impairment the next day, although there are no subjective symptoms of hang-over.

According to their own assertions, all subjects had slept their normal hours before the N-measurements. In the hang-over condition they were awakened after 8 —9 hours in bed. A few of those who were still -above 30 mg% chose to go on sleeping for another hour. Thus, the observed impairment of performance could hardly be ascribed to lack of sleep.

The quality of sleep rather than the amount of sleep might have contributed to the observed changes in performance. Reduced proportions of REM-sleep have been found after alcohol consumption ( Kn o w l e s et al., 1968) and this would

indicate a change in quality of sleep. However, at this point it is not possible to draw the conclusion that the degradation of performance was caused by this change.

The majority of the subjects were students, aged 20—30, and fairly experienced drinkers. W hether this category is somehow different from the general population with regard to susceptibility to the effects of alcohol, is hard to tell since the problem has not been systematically studied. It can be suspected however, that the hang-over effects for inexperienced drinkers could be more pronounced and appear after consumption of less alcohol.

Swedish traffic laws do not permit any driving even for testing purposes if the driver is under influence of alcohol to the degree that his performance is affected.

Therefore, it was not possible to carry out direct comparisons between acute and hang-over effects of alcohol.

Comparisons with earlier results, e. g., the study of small doses of alcohol on driving performance in emergency situations ( La u r e l l, 1977), are not readily

made because the driving conditions, driving task, and performance measurements were different in the different studies. The 1977 study involved three part-tasks, which were compensatory to a certain extent and no composite measure was presented.

In order to be able to make correct judgements as to the seriousness of the observed impairment of driving performance which accompanies hang-over it is also very important to try to compare these results with possible adverse effects of other factors, such as various amounts of sleep deprivation, physical strain, menstruation, cold or fever.

Among the factors which it has not been possible to evaluate in this study are drinking experience and drinking patterns during the drinking bout, i. e. the pace at which the alcohol is consumed, the dilutions etc.

All of these are examples of problems which are brought to the fore by the present results.

S u m m a r y

T h e aim w as to study h an g-over e ffe cts o f alcoh ol on driver perform ance w hen all a lco h o l has been m e ta b o liz e d . T he driving task w as an a void an ce m aneuver putting high d em ands on a tte n tio n , reaction tim e , p recision and coord in ation . E ach o f the 22 subjects participated in an arranged drinking party. T h e day after w hen their B A C w as d o w n to zero the first hang-over driving tests w ere carried o u t. Three hours later the sam e tests w ere rep ea ted . It w as found that driving perform ance w as im paired in both h a n g -o v er co n d itio n s w hen com p ared to the su b jects’ norm al perform ance. T he su b jects acted as their ow n con trols in rotated order o f co n d itio n s.

N o relation sh ip w as found b etw een im pairm ent and subjective w ell-b eing in the h a n g -o v er con d ition .

K e y w o r d s

D riv in g p erform ance, h an g-over e ffe cts — “h a n g -o v er‘\ driving perform ance

Z u s a m m e n f a s s u n g

D a s Z ie l der v o rlieg en d en U n tersu ch u n g war e s , zu priifen, in w elchem U m fang die Spätw irkung von A lk o h o l (p o st-a lk o h o lisch e P hase, „K ater“ ) nach seiner A usscheidung die F ahrtiichtigkeit beeinfluB t. In F ahrversu ch en war ein A u sw eich m a n ö v er durchzufiihren, w obei beson d ers hohe A n fo rd eru n g en an A u fm erk sa m k eit, R ea k tio n szeit. G en a u ig k eit und K oordinationsfähigkeit gestellt w urden. D ie 22 Ver- su ch sp erso n en tranken gem ein sam A lk o h o l, die T estfahrten w urden am anderen T ag d u rch g efiih n , n ach d em die B lu ta lk o h o lk o n zen tra tio n w ied er auf 0 Prom ille abgefallen war. D rei S tu n d en später w urde der gleich e T est w ied erh olt. In b eid en V ersu ch en , die jew eils in der p o st-a lk o h o lisc h e n Phase d urchgefiihrt w urden, liefi sich ein e B eein träch tigu n g der F ahrtiichtigkeit festste lle n , verglich en mit d em F ahrverhalten der b etreffen d en V ersu ch sp erso n , das sie unter norm alen B ed in g u n g en (K ontroll- versu ch ) z e ig te . Es liefi sich jed o ch k ein e B e zieh u n g zw ischen dem subjektiven B e fin d en in der post- a lk o h o lisch en P hase und der B eein trä ch tig u n g d es Fahrverhaltens herstellen.

S c h l i i s s e l w ö r t e r

F ahrtiich tigk eit, p o st-a lk o h o lisc h e P hase - „K ater“ , Fahrtiichtigkeit

R e f e r e n c e s

B o n te , W ., u. J. V olck: U n tersu ch u n g en zum P roblem der A lk oh olnachw irku n gen . B lu ta lk o h o l 16, 3 5 - 4 6 (1978)

E k m a n , G ., M . F ran kenh aeu ser, L. G o ld b e r g , K. B jerver, G . Järpe, A .-L . M yrsten: E ffects o f alcohol in ta k e on su b jective and o b je ctiv e variables o v er a five-hour period. P sych op h arm acologia 4, 28 . . . (1963)

E k m a n , G ., M . F ran kenh aeu ser, L. G o ld b erg , R . H agdahl, A .-L . M yrsten: S u b jective and o b jective e ffe c ts o f alcoh ol as functions o f d o sa g e and tim e. P sychopharm acologia 6, 3 9 9 - 4 0 9 (1964) F o rsa n d er, O ., O. K. V artia and F. E . Krusius: E x p e r im e n te d Studien iiber die b io lo g isch e W irkung

vo n A lk o h o l. I. A lk o h o l und B lu tzu ck er, A n n . M ed. exp. B iol. Fenn. 36, 416 . . . (1958) G o ld , C ., U .-M . R h o , I. R . T ichauer and R . C. W olkenberg: P harm acokinesiological study o f alcoholic

h a n g -o v er. A m erican A sso cia tio n for A u to m o tiv e M edicine. Proc. 17th. O k lahom a C ity, O k l. N ov 1 4 - 1 7 , Pp 3 5 1 - 3 6 3 (1973)

G o ld b e r g , L.: B ehavioral and P hy sio lo g ica l E ffects o f A lc o h o l on M an. P sych osom atic M ed icin e. V o l. X X V III , N o . 4, Part I I ., Pp 5 7 0 - 5 9 5 (1966)

K elly , M ., A .-L . M yrsten, A . N eri and U . R ydberg: E ffects and after-effects o f alcoh ol on p sy ch o lo g i­ cal fun ction s in man - a con tro lled study. B lu talk oh ol 7, 4 2 2 - 4 3 6 (1970)

K n o w les, J. B ., S. G . L averty and H . A . K uechler: E ffects o f alcoh ol on R E M sleep . Quart J Stud. AJc.

29, 3 4 2 - 3 4 9 (1968)

L au rell, H .: E ffects o f sm all d o ses o f alcohol on driver perform ance in em ergen cy traffic situ ation s. A ccid . A n a l. & Prev. 9, . . . (1977)

M yrsten, A .- L ., M . K elly, A . N eri, U . Rydberg: A cu te effe cts and after-effects o f alcoh ol on psy ch o lo g ica l and p h ysiological functions. P sychological lab. U n iv . o f S tockh olm . R eport N o . 314. D e c . 1970

M yrsten, A . L ., U . R yd b erg, C .-M . Ideström and R . Lam ble: A lc o h o l intoxication and han-gover: m o d ifica tio n o f h an g-over by C h lorm eth iazole. P sych op h arm acology 69, 1 1 7 -1 2 5 (1980)

S ep p ä lä , T ., T . L e in o , M . L in n o ila , M. H u ttu n en and R . Ylikahri: E ffects o f h ang-over on p sych om otor skills related to driving: m odification by fructose and g lu co se . A cta pharm acol. et to x ico l. 38, 2 0 9 - 2 1 8 (1976)

S ie g e l, S.: N on p aram etric statistics for the behavioural scien ces. M cG raw -H ill, N ew Y ork (1956) S ten in g , G ., and I. D u rem an : A k u ta och p osttoxisk a effek ter av alkohol på prestation i bilsim ulator.

U n p u b lish ed report. D e p t, o f P sy ch o lo g y , U p p sala (1974)

T ak ala, M ., E . Siro and Y . T oivain en : In tellectu al functions and d exterity during hang-over. E x p er i­ m en ts after in to x ica tio n with brandy and with beer. Q uart. J. Stud. A le . 19, 1 - 2 9 (1958) T ich au er, E . R ., R . C. W olk en b erg and Y . M . R ho: D e la y e d effects o f acute alcoholic in toxication on

o ccu p a tio n a l safety and h ealth. T h e C enter for Safety and the Institute o f F orensic M ed icin e, N ew Y ork U n iv ersity . U n d a te d PM .

V artia, O , K ., O . A . F orsan d er and F .-E . Krusius: B lo o d sugar in hang-over. Q uart. J. Stud. A le . 21, 5 9 7 - 6 0 4 (1960)

A n s c h r i f t e n d e r V e r f a s s e r :

H an s L au rell, B . Sc. R esearch p sy ch o lo g ist,