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DRIVER FATIGUE AND STIMULANTS
Prepared by
Narelle L Haworth
Monash University Accident Research Centre
October 1989
MR5
DEPARTMENT OF TRANSPORT AND CO~~UNICATIONS
FEDERAL OFFICE OF ROAD SAFETY
EOCUHENT RETRIEVAL INFORMATION
Date
Report N o .
MR5
Pages
O c t 1989
13
ISBN
ISSN
0 6 4 2 51347 3
1034-3830
T i t l e and Subtitle
Driver Fatigue and Stimulants
A u t h o r ( s1
Narelle L Haworth
PerformingOrganisation(Name
and A d d r e s s )
Monash U n i v e r s i t y Accident R e s e a r c h C e n t r e
CLAYTON
VIC
3168
sponsor
F e d e r a l O f f i c e of Road S a f e t y
GPO BOX 594
CANBERRA ACT 2 6 0 1
Available
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GPO Box 594
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Abstract
The r e l a t i o n s h i p b e t w e e n d r i v e r f a t i g u e a n d t h e
u s e of s t i m u l a n t s i s
r e v i e w e d .W h i l e
l i t t l e i n f o r m a t i o n i s a v a i l a b l ea b o u ts t i m u l a n tu s e
by
cardrivers,Australianandoverseassurveyshave
shown t h a t a b o u t
40-60%of long d i s t a n c e t r u c k d r i v e r s h a v e r e c e n t l y u s e d s t i m u l a n t s
for
t h e p u r p o s e of k e e p i n ga w a k ew h i l ed r i v i n g .T h ep h a r m a c o l o g y
of t h e
most widely u s e d s t i m u l a n t s i s d i s c u s s e d , as a r e e f f e c t s of these
is c u r r e n t l y i n s u f f i c i e n t
s t i m u l a n t so nd r i v i n gb e h a v i o u r .T h e r e
of s t i m u l a n t s
e v i d e n c e t o e n a b l e c o n c l u s i o n s t o be d r a w n a b o u t t h e r o l e
i n r o a dc r a s h e s .
Keywords
DRUGS,
DRIVER BEHAVIOUR, FATIGUE, ROAD CRASHES
NOTES:
(1)
FOES Researchreportsarcdisseminated
i n t h ei n t e r e s t s
of i n f o r m t i m exchange.
( 2 ) The vieusexpressed art those of the author(s) ard do not necessarily represent those
(3)
The
(a)
(b)
(c)
(d)
of t h e C m n u e a l r h Government.
FederalOfficeof
Rod Safety publishes f o u r s e r i e s of researchreport
reports generated B S a r e s u l t of research dclc uithin the FORS a r e p h l i s h e d i n the OR s e r i e s ;
reports of research cwducred by other organisatims on behalf of the FORS are prblished i n the C R s e r i e s .
reports based on analyses of FORS' s t a t i s t i c a l d a t a bsses are published in the
SR s e r i e s .
minor reports of research cor&lcted by other organisations m b d a l f of FORS are prblished in the M R s e r i e s .
EXECUTIVE SUMMARY
The relationship between driver fatigue and the use of stimulants is reviewed in the four
sections of this report. While little information is available about stimulant use by car
drivers, Australian and overseas surveys have shown that about 40% to 60% of long distance
truck drivers have recently used stimulants for the purpose of keeping awake whiledriving.
Amongst car drivers, caffeine is probably the most widely used stimulant. The stimulants
used locally by some truck drivers include amphetamine and two amphetamine derivatives,
Tenuate Dospan and Duromine. There is also some evidence that ephedrine, another class of
stimulant, is used. The pharmacology of these drugs is discussed in the secondsectioh of the
report.
The effects of a single administration of a stimulant on driver alertness are Likely to be
positive. In the laboratory and on the road, caffeine has been shown to lead to improvements
on a number of measures of driver alertness, inchding reaction time to changes in the
distance to the simulated vehicle in front. A large number of studies have investigated
whether the stimulant effects of caffeine can be used to counte.ract the depressant effectsof
alcohol. The results of these studies have been mixed and it appears that any effects may be
dose-specific.
The effectsof amphetamine and amphetamine derivatives on many behaviours have been
studied, some of which are relevant to driving. Vigilance performance is improved with
ingestion of d-amphetamine (but not I-amphetamine). Amphetamine derivativesmay
improve attention and partly restore performance affected by alcohol. Amphetamines may
affect driving by a direct effect on visual perception. Administration of amphetamines may
lead to an increase in risk taking in driving and a deterioration in accuracy of judgement of
speed.
It is likely that the prolonged use of amphetamine and amphetamine derivativesmay result in
an increased risk of a road crash because of the Occurrence ofvisual hallucinations and the
massive onset of fatigue experienced by amphetamine-dependent drivers whoare unable to
secure sufficientdosages.
An estimation of the conmbution of stimulant abuse to road crashes cannot be madeas yet
because of the paucity of information about the frequencies of crash-involved and non-crashinvolved drivers who had used stimulants. A very rough estimate from local and overseas
studies is that about three percent of drivers in fatal accidentshad taken stimulants. One
study showedthat amphetamine abusers had poorer driving histories than other drivers but
this may have been due to another characteristic of the sample.
In summary, caffeine is the stimulant most widely used by drivers and few detrimental effects
have been reported. The effects of stimulants on driver fatigue depend largely on dose and
prior history of usage. Further investigation of possible differences in magnitude of response
as a function oftime of day is needed. There is insufficient evidence to enable conclusions to
be drawn about the role of stimulants in roadcrashes.
1 Introduction
The relationship between driver fatigue and the use of stimulants is reviewed in the four
sections of this report. The extent of usage is outlined from surveys conducted in Australia
and overseas and the drugs used locally are identified. The pharmacology of these drugs is
then discussed in the second section. Studies of the effects of stimulants on driving and
evidence of the role of these drugs in road crashes are presented.
2 Extent of usage
The extentof usage of caffeine by car drivers is likely to be similar to that of the general adult
population. A US study (Graham, 1978) estimated the mean adult intake of caffeine to be
186 mg perday (227 mg/day when those who tookno caffeine were excluded). These intakes
are equivalent to 2.2 and 2.7 cups of coffee, respectively. Eighty-two percent of the adults
surveyed consumed caffeine. The usage of caffeine may be a little lower in Ausualia bur is
likely to be similar.
Australian and North American surveys of drug use by truck drivers have been published. In
the US state of Tennessee, Lund,Preusser, Blomberg and Williams (1987) found that 29
percent of the tractor-trailer (semi-trailer) drivers in their survey had evidence of alcohol,
marijuana, cocaine, and/or prescription or nonprescription stimulants in either blood or urine.
Nonprescription stimulants (phenylpropanolamine, ephedrine, pseudoephedrine) were found
in 12 percent and prescription stimulants such as amphetamine were found in five percenr
In a Canadian study, 37% of tractor-trailer drivers knew drivers who used stimulants other
than tea or coffee to keep alert while driving a truck (Transport Canada, 1987). Detailed
analyses of responses suggested that the drivers were to some extent reporting their own
behaviour when asked about that of other drivers. Owner drivers were more likely to report
knowing drivers whoused stimulants than were employee drivers (43% vs. 34%).
Usage of stimulants by other drivers was also reported by many of the 878 articulated vehicle
drivers who completed the 1988 Regular Common Canier Conference Safety Survey (cited in
Insurance Institute for Highway Safety, 1989).
Guinn (1983) asked a sample of Texas owner drivers to'estimate theirfrequency of drug use
while trucking. As Table 1 shows, 62.5% of drivers responded "Sometimes", "Often" or "All
the time" when asked "How often in the past year have you used drugs (except vitamins,
aspirin, No-Doz and similar over-the-counter preparations) for the purpose of remaining
awake and alert while trucking?".
Table 1. Self-reported frequency of drug use in the past year for the purpose of
remaining awake while driving. From a survey of Texas owner-drivers by Guinn
(1983).
Frequency
Never
Rarely
Sometimes
Often
All the time
Number of drivers
22
20
38
21
11
drivers
Percent of
19.6
17.9
33.9
18.8
9.8
The study found that drug use by truck drivers was not correlated with job dissatisfaction,
contrary to a common view in work psychology (Mangione and Quinn, 1975; Perone,
DeWaard and Baron, 1979). Drug use by truck drivers appears to be motivated by the desire
to remain awake, not boredom as found in other occupations.
The incidence of drug usage by truck drivers is Likely to be similar in Ausnalia. Nix-James
(1977) presents self-report data on usage of alcohol and alerting medications by long-distance
heavy vehicle drivers in NSW. When asked how often they take "stay-awake pills", 14%
responded that they "often use them" and 27% answered that they "sometimes use them".
Whilst these surveys give an indication of the extent of drug use by truck drivers, they give
little infomation about the exact preparations taken, dosages and time factors involved. In
order to gain more detailedinformation, a number of agencies were contacted.
The Victorian Drug Information Centre (VDIC) provided information that the two
amphetamines legally available in Victoria are amphetamine and dexuamphetamine. These
are scheduled as drugs of addiction by the Victorian Department of Health and are only
available for the treatment of narcolepsy and hyperkinesis, and then only by applying to the
Department for permission to prescribe. The VDIC suggested that truck drivers might use
amphetamine derivatives, rather than amphetamine itself and that Direct Line, who advise on
aspects of illicit drug use, be contacted.
Direct Line were not sure that truck drivers used amphetamines per se. They recalled that
Fedrine (ephedrine hydrochloride) was said to be used. This drug is most commonly used for
the treatment of asthma andis easier to obtain than amphetamines because it isnot scheduled
as a drug of addiction. Interestingly, in the analysis of Coroners reports of fatal crashes
involving trucks (Haworth, Heffernan and Home, 1989), one driver stated that he was a
regular user of Fedrine but had not taken any in the last 24 hours. This is in accord with the
view that withdrawal fiom stimulant drugs may impair performance.
The Alcohol and Drug Foundation suggested that Durophet, a mixture of amphetamine and
dexamphetamine sulphate, is used by truck drivers.
Information from another source (reliable but anonymous) indicated thattruck drivers in
Victoria most commonlyuse amphetamine derivatives which are prescribed as appetite
suppressants. The dosages and drugs taken depend on the length of time the driver has been
taking stimulants. This results from the build-up of tolerance to the drug, a decreased
response to a constant dosage of the drug. Some drivers begin taking TenuateDospan tablets,
which are referred to colloquially as "briquettes". As tolerance develops, the dosage islikely
to be increased from one up to five tablets. When increased tolerance results in Tenuate
Dospan losing the desired stimuIant effect, drivers are said to change to Duromine. The
degree of dependence on such drugs is underlined by reports that dependent drivers will take
them for short trips as well as long ones.
3 Pharmacoloev o f some stimulants used bv drivers
This section begins with a description of the pharmacology ofthe most widely taken
stimulant, caffeine. Amphetamine and amphetamine derivatives, including Tenuate Dospan
and Duromine are then described. The pharmacology of ephedrine (Fedrine) is also outlined
3.1 Caffeine
Caffeine, theophylline and theobromine are three xanthine compounds that are obtained from
plants. Caffeine is 1,3,7-t~imethylxanthine;theophylline, 1,3-dimethylxanthine; and
theobromine, 3.7-dimethylxanthine. Tea contains caffeine andtheophylline, coffee and cola
drinks contain caffeine only and cocoa contains caffeine aid theobromine. Caffeine is the
most important and widely used of the three related stimulants.
The traditional view is that caffeine and theophylline act by inhibiting phosphodiesterase, the
enzyme that breaks down cyclic AMP. However, recent work suggests that there is little
inhibition of phosphodiesterase at the maximal therapeutic concentrations of drug inplasma
and that the drugs function by blocking adenosine receptors.
The half-life of caffeine is about 3 to 4 hours but this is affectedby a number of factors. The
half-life is approximately doubled in women during the later stages of pregnancy and with the
chronic use of oral contraceptive steroids (Patwardhan, Desmond, Johnson and Schenker,
1980). Caffeine is metabolised more quickly by individuals who smoke (Parsons and'Neims,
1978).
Caffeine is rapidly absorbed and maximal plasma concenaations are achieved withii an hour.
The ingestion of 250 rng of caffeine leads to concentrations in plasma of about 10
micrograms/milliliue. About 1% of administered caffeine is recoveredin the urine
unchanged. The principal metabolites are 1-methyluric acid and 1-methylxanthine.
The xanthines relax various smooth muscles other than those of blood vessels. This includes
the muscles of the bronchi and theophylline, particularly, has been used in thetreatment of
bronchial asthma. Caffeine increases the capacity for muscular work in man by increasing
muscle tension.
Both caffeine and theophylline stimulate mental activity; thought is more rapid and fatigue is
removed or its onset delayed. The effects on mental and physical performance vary
according to the state and personality of the subject. Reaction-time is decreased.
Performance that is inferior because of excessive anxiety may become worse (Laurence and
Bennett, 1980).
Whilst caffeine produces an increased capacity for sustained intellectual effortand decreases
reaction time, tasks involving delicate muscular coordination may be adversely affected.
These effectsmay be produced by the administration of 85 to 250 mg of caffeine, the amount
contained in 1 to 3 cups of coffee.
Caffeine and amphetamine have been said to have similar effectson performance and mood
They both improve physical performance in tasks like athletics or monitoring controls. It is
unclear whether the improvement is due to reduction in impairment by fatigueor boredom or
to improvement onnormal maximum performance. Hand steadiness is decreased by caffeine
and increased by amphetamine, however. The drugs also differin the degree of dependence
which develops: amphetamine dependence may result in psychosis(Ellinwood, 1969;
Ellinwood and Kilbey, 1980) whereas tolerance to the stimulant effects of caffeine does not
develop but withdrawal produces headache (Graham, 1978).
Both caffeine and amphetamine cause increased cardiac output, tachycadia and sometimes
ectopic beatsand palpitations. This effect occurs almost at once after i.v. administration and
lasts half an hour. Changes in blood pressure arc not always predictable but250 mg caffeine
usually causes a transient increase in blood pressure of about 14/10 mm Hg. Caffeine has
been reported as producing mutations in DNA but the concentrations at which this occurs are
well above those commonly found in plasma (Rall, 1985).
3.1.1 No Doz. No Doz is the brand name of caffeine tablets available over-the-counter.
Each tabletcontains 100 mg of caffeine which is equivalent to one to two cups of tea or
coffee. It is likely that they are considered not strong enough stimulants by truck drivers.
Pharmaceutical guides state that No Doz may be used in cases of "mental fatigue",
drowsiness and general inertia (Craig, 1986). The dosage recommendedis one tablet with no
~.
repeats given within three hours of administration and a maximum of six tablets in 24 hours.
It is suggested that this dosage be reduced if the individual drinks tea, coffee or cola drinks.
3.2 Amphetamine
Amphetamine is the common name for 1-phenyl-2-aminopropane. The chemical has two
forms: dextro and levo, of which the former is the most powerful cennal nervous system
stimulant. For pharmaceutical purposes dextramphetamine and a racemic mixture, commonly
termed amphetamine, are available.
Amphetamine acts by releasing noradrenaline stored in nerve endings in both the central
nervous system andthe periphery. Its psychological effects vary with mood, personality and
environment as well as dose. Both amphetamine and ephedrine are stimulants for adults but
sedatives for children, hencethe use of amphetamines in the treatment of hyperkinesis
(Laurence and Bennett, 1980).
Amphetamine is usually given orally, but it can be injected. The plasmahalf-life of
amphetamine is ordinarily about 12 hours. Amphetamine sulphate is a white, water-soluble
powder. The toxic dose of amphetamine varies widely, Toxic manifestations are rare with
doses of less than 15 mg. Larger doses can be tolerated after chronic use of the drug. The
use of amphetamine is inadvisable in patients with anorexia, insomnia, asthenia,
schizophrenia, psychopathic personality, or a history of homicidal or suicidal tendencies.
The effects of amphetamine differ markedly with dose and history of administration. The
effects of small, acute doseswill be described, followed by the effects in prolonged
administration.
Amphetamine has both peripheral and central nervous system effects. Small doses of
amphetamine raiseblood pressure and slow heart rate. Increases in motor and speech activity
are often observed. Side-effects may include anxiety and a feeling of nervous and physical
tension and the subject may show tremors and confusion, and feel dizzy.
In general, studies of the alerting effects of small acute doses of amphetamine have shown
smaller effects for interested, motivated, kesh subjects than for fatiguedsubjects (Kornetsky,
1969). A slight improvement in physical performance is foundinathletic performance when
amphetamine is administered but the magnitude of this improvement is small. The greatest
improvement occurs when performance of physical or mental tasks has been reduced by
fatigue and loss of sleep (Weiner, 1985). Such improvement may be panly due toalteration
of unfavourableattitudes toward the task. However, amphetamine reduces the frequency of
attention lapses that impair performance after prolonged sleep deprivation, and thus improves
execution of tasks requiring sustainedattention.
Amphetamine administration may impairthe subject's judgement of hisher performane,
however (Laurence and Bennett, 1980). The subject may be more confident and better
satisfied with a performance which has, in fact, deteriorated in accuracy as well as being more
speedily accomplished.
As long as they are taken irregularly andin low or moderate doses, amphetamines do not
appear to pose any behavioral or psychological problem. As with most other psychoactive
drugs, the problems arise from high doses and habitual use. And once use becomes habitual,
tolerance develops, and accordingly higher doses become necessary. It is unclear whether
amphetamine producesme physicd dependence but withdrawal effects havebeen observed.
Kornetsky (1969) has remarked that "upon abrupt termination after chronic use, depression is
often seen accompanied by fatigue and lasitude, and there is evidence of EEG changes"
(p.234).
Amphetamine psychosismay develop as a result of continued high doses (or perhaps from a
single high dose). The features of the syndrome are delusions of persecution, ideas of
5
.
reference, visual and auditory hallucinations, change in body image and hyperactivity and
excitation, but without disorientation or clouding of memory (Ellinwood, 1969).
3.3 Amphetamine derivatives
Dexamphetamine (Dexedrine in the US) is similar to amphetamine (Benzedrine) and is
available in Australia. It is three or four times as powerful in eliciting central nervous system
effects as 1-amphetamine. Methamphetamine (Methedrine) is similar to amphetamine but its
effects on the cennal nervous system are greater. Other amphetamines are phenmetrazine
(Preludin), phentermine (Duromine), diethylpropion (Tenuate). methylphenidate (Ritalin,
often used in hyperkinesis), pemoline (Kethmed) and meclofenoxate (Lucidril).
3.3.1 Tenuate Dosuan. Tenuate Dospan is diethylpropion hydrochloride (75 mg) in a
hydrophilic colloid gum designed to release the ingredient over a 10 hour period. Its chief
action is the reduction of food intake but it results in "some CNS stimulation" (Craig, 1986).
The excretion half-life for diethylpropion hydrochloride and its metabolites is about 10 hours.
Craig (1986) recommends that one tablet should be taken midmoming and that doses may be
given over periods up to 12 weeks, with intervening periods of one monthwithout matment.
This dosage appears to be exceeded by most truck drivers using Tenuate Dospan as a
stimulant. It is also interesting to note that a warning is given that the drug may interfex with
operating machinery or driving a motor vehicle in some patients and that the patient should
be cautioned accordingly.
It is reported that cases of abuse have been uncommon and that most abusershad previously
abused other stimulants (Craig, 1986). Tenuate does not seem to give rise to pleasurable
sensations and rarely leads to hallucinations, even when high doses are administered. There
are some reports of anxiety and agitation as the drug wore off. In overdosage fatigue and
depression usually follow the central stimulation.
3.3.2 Duromine. Duromine is the trade name for phentermine, an amphetamine derivative.
It is prepared as capsules containing an ionexchange resin for sustainedrelease. The
recommended use of Duromine is formanagement of obesity as a short term adjunct to
calorie resaiction in weight loss.
The drug comesin 15,30 and 40 mg capsules and the recommended dose isone daily at
breakfast. The stzength admmistered depends on the body weight of the individual andany
evidence of sideeffects. A warning is given not to exceed the recommended dose.
The drug should not be taken by persons with hypertension or other cardiacdisorders, or
glaucoma.
3.4 Ephedrine
r
The central nervous system effects of ephedrine are less pronounced than those of the
amphetamines. The drug stimulates the release of norepinephrine and also has direct effects
on receptors. Ephedrine elevates systolic and diastolic blood pressure by some
vasoconsaiction and a greater amount by increasing the force of myocardial contraction,
resulting in augmented cardiac output The relaxation of the bronchial muscle brought about
by ephedrine has led to its use in the treatment of mild and chronic asthma.
Ephedrine sulphate is the 1 isomer and is available in capsulesand syrups, the oral dose varies
from 15 to 50 mg. For continued medication, small dosesare given at 3 to 4 hour intervals.
6
4 Studies of the effects of stimulants on driving
Studies of the effects on driving of caffeine and amphetamine and its derivatives are
presented. Those studies which considered previous history of usage are likely to be more
valid than others which did not. In addition, the generalisability of results of the studies
depend on a number of factors including conditioned responses and time of day effects.
Stimulants may be like other drugs in exhibiting conditioned response effects. For example,
the effect of caffeine taken by drinking caffeine may be composed of the pharmacological
effects of the drug and the conditioned effect of relaxing and drinking coffee. The
conditioned effect may be quite strong and thus studies which administer caffeine by tablet
may not be sensitive to the conditioned response effect. In general, studies which administer
stimulants by the usual route andin the usual environment are more likely to produce valid
results.
Time of day effects have been little studies in relation to stimulant use. There may be some
interaction between circadian rhythms and drug effect that leads to differences in the response
to a drug depending on time of day. This has been suggested by some research currently
underway at Monash University (Redman, personal communication) into the effect of
caffeine at different times of day.
4.1 Caffeine
The effects of caffeine have been studied in on-road driving and in the laboratory.
In an on-road study, Lisper, Tomros and van Loon (1981) examined the effects of caffeine or
diazepam on subsidiary reaction time in a three-hour driving task. Caffeine gave shorter
reaction times during thefirst half of the trip.
Regina, Smith, Keiperand McKelvey (1974) gave subjects 200 mg of caffeine before 90
minutes of operation of a driving simulator and then another 200 mg before another 90
minutes on the simulator. Thev allowed 30 minutes between ineestion of caffeine and
commencement of the task. f i e y note that blood caffeine was k e l y to have been higher in
the second half of the study.
~
~
~~
~~~~~~~~~~~
Both the initial and supplemental doses of caffeine significantly enhanced performance
compared to the placebo on four measures of alertness (response time to lead car
decelerations, lead car accelerations and presentations of the high beam signal and number of
missed high beam signals).
The effectsof caffeine on a four hour visual monitoring task similar to an aspect of night-time
driving were examined by Baker and Theologus (1972). Subjects monitored two red lights
that moved apart at random intervals. This simulated the rear lights of a car being followed at
night. Reaction time measures showed that caffeine significantly reduced attention lapses.
No differences were found between administration of 200 and 400 mg of caffeine.
The magnitude of the behavioural effects of caffeine may depend on the everyday
consumption rate of the user. Childs (1978) demonstrated that subjects who drank less than
three cups of coffee per week experienced an increase in reaction time in short-term visual
scanning when administered 4oOmg of caffeine. In contrast, subjects who commonly drank
larger amounts reacted to the 4OOmg dose with a decrease in RT. Childs concludes that a
large dose ofcaffeine may disrupt visual attention in subjects who are low caffeine users but
may be beneficial for high caffeine users. American estimates of daily intake of caffeine
show that 82% of the population consume caffeine and the mean daily intake is markedly
larger than t h e cups of coffee per week (Graham, 1978), putting most people into the high
caffeine user group.
7
A number of studies of whether caffeine can counteract the performance decrements induced
by alcohol have been conducted (see Mattila, 1981 and Moskowitz, 1981 for reviews).
Franks, Hagedom, Hensley,Hensley and Starmer (1975) studied the effect of caffeine alone
or in combination with alcohol on cognitive, perceptual and motor functions. Caffeine led to
a significant increase in body sway and a decrease in manual dexterity 40 minutes after
ingestion. Ingestion of caffeine did not reverse the ethanol-induced decrement in
performance except in the reaction t i e tests.
The effects of different doses of caffeine and/or ethanol was investigated by Moskowitz and
Burns (1981). In Experiment 1 they administered 4.4 mg of caffeine per kg of body weight
(average dosage 325 mg). In Experiment 2 the dosages were 0.2.93 and 5.87 mg caffeinekg
of body weight (mean doses 0.211 and 423 mg, respectively). Low levels of caffeine
counteracted effects of low levels of alcohol on attention, perception and tracking, but higher
level of caffeine were relatively less effective in offsetting higher levels of alcohol. At no
level was caffeine ableto counteract alcohol's impairment of information processing as
measured by backward masking.
4.2 Amuhetamine and amphetamine derivatives
-
-.
,
The effectsof amphetamine and amphetamine derivatives on many behaviours have been
studied, some of which are relevant to driving.
Collins (1977) administered 10 mg of d-amphetamine to young men who had beendeprived
of sleep for 55 hours. This led to reduced tracking error in both static (no motion) and
dynamic (whole-body angular acceleration) conditions. This study also pointed out that
effects of stimulants may differ when testing occurs in static anddynamic situations. Most
laboratory investigations of stimulants have used a static environment while driving itself
takes place in a dynamic environment.
The effect of 1- and d-amphetamineon vigilance performance, waldng EEG patterns and
-
mood were studied by Hartmann, Orzack and Branconnier (1977). Performance of the 50minute vigilance task'was significantly better for subjects who had taken d-amphetamine than
those who had taken 1-amphetamine. Performance with 1-amphetamineand placebo groups
did not differ. EEG alpha-band activity after sleep deprivation was decreased for subjects in
the placebo and 1-amphetamine groups but not for the d-amphetamine group. No effects of dor l-amphetamine on mood (as measured by the POMS scale) was evident.
The effects of phentermine and methamphetamine have also been studied. In the research
conducted by Truijens, Trumboand Wagenaar (1976), 20 mg of phentermine HC1 was selfadministered by suppository 90 minutes before testing. Subjects were medically examined in
the two days prior to testing. There were three sessions, each comprising 33 120-second
trials. Administration of phentermine led to better performance in a randomization task (a
test of memory and attention) and lower integrated error scoreson a pursuit tracking task.
The effectof methamphetamine on ethanol-induced driving impairment was investigated by
Rutenfranz and Jansen (1959, inMattila. 1981). Administration of 9 mg of
methamphetamine restored simulated driving performance after O.Sg/kg ethanol but only
partially restored performance after 1.0 @g.
Amphetamines may affect driving by a direct effect on visual perception. Westheimer (1963)
studied the effects of dextroamphetamine sulphate (Dexedrine) and racemic amphetamine
sulphate (Benzedrine: 15 mg) and barbiturates on accommodatiodconvergence. The two
amphetamines activated the accommodation mechanism to the same degree and tightened the
accommodatiodconvergence synkinesis. Tests were conducted for eighthours or longer.
a
Some concern exists about the effects of amphetamine on decision-making aspects of driving.
Amphetamines may produce a misjudgement of speed (Ashworth, 1975) and an increase in
risk t&g (Hurst, 1962 in Hurst, 1976).
5 The role of stimulants in road crashes
Certain stimulant drugs are used by some drivers to help them keep awake. Regular use of
stimulant drugs to stay awake for longperiods of time may lead to hallucinations and
impaired performance, which increases crash risk.
In addition the repeated use of some stimulants, such as amphetamines, leads to tolerance of
the drug, so increasing amounts are required to maintain alertness (Milner, 1972). The
problem of drug dependency in this situation means that driving performance could be
expected to reduce dramatically when sufficiently high levels of amphetamines were not
available to meet the body’s increased demand forthem. The bodywould not be able to
function with a normal (i.e., drug free) level of performance unless some level of
amphetamines were present. This need for increased dosages of amphetamines to maintain
even normal alertness levels means that amphetaminedependent drivers who are unable to
secure sufficient dosages may actually become more fatigued than would normally be the
case if no drugs were used (Goodman and Gillman, 1965).
The development of dependence on stimulant drugs means that their use mayresult in
increasing the possibility of a fatigue-related crash, rather than the reverse.
There is very little information about the usage of stimulants by crash-involved drivers. They
cannot be detected by breath testing and urine testing is not commonly conducted. The likely
true rates of incidence are low (markedly less than 10%) which means that test refusal rates
may lead to large errors inestimating the incidence of amphetamines in crashes. If only 1%
of the tested drivers are positive for amphetamines, and the test refusal rate is 5%, then the
m e incidence may be nearly 5 times as great as the observed value murst, 1976). Terhune
(1986) has reviewed the problems and methods in studying drug crash effects.
In one of the earliest examinations of the role ofdrugs in crashes, Davisand Fisk (1966, cited
in Hurst, 1976) investigated fatal single vehicle crashes in Dade County, Florida. Only 8 of
the 179 victims had taken a drug other than alcohol and 4 of these had ingestedalcohol as
well.
~
A study of the incidence ofdrugs in road crash fatalities in England and Wales was reported
by Everest, Tunbridge and Wlddop (1988). The stimulants which were tested for were
caffeine, amphetamine, amphetamine derivatives and ephedrine. The incidence in which
caffeine was detected was not reported. Amphetamine was detectedin three of 116 fatalities
tested.
Hendtlass (1985) has reponed a study of drug involvementin fatal crashes in Melbourne. Of
178 drivers,motorcycle riders or pedestrians who were foundto have used drugs other than
alcohol, caffeine or nicotine, amphetamines had been used by 4 operators (2.2%). Three of
these operators were under 25 and the other was aged between 25 and 4 4 . In 15 cases
ephedrine had been used by the person killed. Caffeine was present in64.4% of fatalities
analysed.
Studies conducted in metropolitan areas may underestimate the role of stimulants in road
crashes. The useof stimulants is likely to be primarily to remain awake during long distance
travel, which is by its nature largely rural.
An alternative approach to determining the role of drugs in roadcrashes was taken by Smart,
Schmidt and Bateman (1969). They examined the crash records
of eight amphetamine
abusers (and abusers of other drugs). Drivers who abused amphetamine alone had over four
9
times as many crashes as would be expected on the basis of age, sex, mileage and driving
experience. Drivers who abused other drugs in addition to amphetamines had about twice the
expected crash frequency. These results suggest that amphetamine abuse increased crash risk
but there may have been some other characteristic of the sample which led to the greater
frequency of crashes.
10
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