The effects of secobarbital, diazepam, alcohol, and marihuana on car-driver transfer functions obtained using a driving simulator were studied. The first three substances, all CNS depressants, reduced gain, crossover frequency, and coherence which resulted in poorer tracking performance. Marihuana also impaired tracking performance but the only effect on the transfer function parameters was to reduce coherence

Moskowitz, H.

Smiley, A.

Ziedman, K.

English

NASA Technical Reports Server

1.J
N82"1 370 9 :
M_NUAL CONTROL ANALYSIS OF DRUG EFFECTS ON
DRIVING PERFORMANCE*
By Alison Smiley, Ker,nethZiedman and
Herbert Moskowitz
Southern California Research Institute
SUMMARY
:" _ Effects of secobarbital, diazepam, alcohol and marihauna on car-
dFiver transfer functions obtained using a driving simulator were studied.
The first three substances, all CNS depressants, reduced gain, crossover
frequency and coherence which resulted in poorer tr_cking performance.
Marihuana also impaired tracking performance but the only cffect on the
trarJsferfunction parameters was to reduce coherence.
INTRODUCTION
Manual control analysis of tracking performance has been most frequently
used to study changes in task variables, such as controlled element dynamics,
rather than operator variables such as fatigue, or drug effects. This paper
addresses the issue of drug effects on the tracking behavior of human operators,
a topic of great interest because of its importance to traffic safety. The
drugs studied were secobarbital, a sedative hypnotic, diazepam, a widely
prescribed sedative minor trcnquilizer, and marihuana, a common recreational
drug. The diazepam and marihua-c were combined with alcohol.
The transfer function _p_,oach for examining drug effects was chosen for
two reasons. First, it allo+_ssome dlfferention between drugs in terms
of which aspects of perceptual-motorbehavior are being affected. Spcond,
it providps a unified framellorkin which to interpret results, unlike the
interpretationof an assortment of tracking parameters.
There have been few published studies of drug effects on trarsfer
function parameters. Allen et al (reference I) using both an instrumented
car and a driving simulator found the effect of alcohol was to reouce the
driver's gain and decrease the coherence (i.e., the driver became a less
respohsive and less linear tracker). Reid (reference 2) calculated describ-
ing functions for subjects performing a compensatory tracking task under the
influence of alcohol alone and in combination with marijuana. Similar effects
of reduced gain and reduced linearity of response were found as well as an
increase in subject internal processing time. All these changes in control
* This work supported by The National Institute on Drug Abuse and The
National Highway Traffic Safety Administration under NIDA Contract No.
271-16-3316 lie j_'o_.
a |
1982005792-494
https://ntrs.nasa.gov/search.jsp?R=19820005836 2020-03-21T15:58:24+00:00Z
contributed to degraded tracking performance.
Trackir,gtask measures related to transfer function parameters have
been used to distinguish between the effects of different drugs. Smilev
et al. (reference 3) compared the effects of alcohol alone an_ in combination
with diazepam, diphenhydramine (an antihistamine) and marihuana on driving
in atlinstrumented car. The power spectra of steering wheel angle, a measure
of the amplitude of steering movement over a range of frequencies, showed:
(I) that subjects made larn_r steering movements under the alcohol +
diphenhydramine,alcohol + marihuana and alcohol alone treatments when
compared to placebo, and smaller njvements under the alcohol + diazepam
treatment and (2) that subjectt' steering movements were slower under all
drug treatments, and slowest for the alcohol + diazepam condition, when compared
with placebo.
I
PROCEDURES
Drug Treatments: The results reported in this paper are derived from
three separate experiments on the effects of drugs on human performance.
The first experiment examined secobarbital alone at three do_.ele!_.]_s.L__
rb,'_._"dlIb_," mg_'Kg'oobywe'Ightusing 15 subjects. The second and third
experiments w_re drug alcohol interaction studies with the drug and the alcohol
each tested at three levels. A separate group of 15 subjects was tested at
each alcohol level, maki,,ga total of 45 subjects tested in each of the
twe studies. Each subject received all three drug doses. Dose levels used
in the second experiment were: diazepam: O, 0.!I, 0.22 mg/kg bodyweight and
a]cohol: O, 0.51, and 1.02 gms/kg bodyweight. For the third experiment
_ose levels were: marihuana: O, 100, 200 mcg THC/kg bodyweight and alcohol:
O, 0.425 and 0.68 gms/kg bo,_vweight. The alcohol was administered in a vodka-
orange juice mixture, the di_,zepamand secobarbital by capsules, and the
marihuana by smoking.
The dose levels of secobarbital and diazepam were those generally used
in therapeutic situtations. The highest dc,se level of alcohul produced a
blood alchol concentration (BAC) of 0.11%, just over the 0.10% _AC legal
presumptive limit fur impariment in California. A questionnai,e, given to
the subjects who received marihuana, showed that the 100 ana 200 mcg
THC/mg bodyweight doses produced the same "high" as the subjects experienced
in their social use of marihuana between "less than half the time" and
occasionally".
Subject_: Participants met the foll_wing criteria: male, 2_k-45years
)Id, 61.5-91 kg bodyweight, 20/30 mini),,_',vision in each eye, moderate
_o lioht heavy alcohol use as defined bj'the CBhalan et al (refer+,nc_4)
scale, and having it least three years driving experience. Subjects
were screei_edusing a medical examination and a _t.'ndardizedpersonality
test for possible physical or emotional counter indications.
• F
Testing Schedule: Subjects attended three training days within a i
-S04-
c
1982005792-495
three-week period. On each training day subjects completed two forty-five
minute simulator runs. After training, subjects attended three treatment
sessions separated by two week intervals. At each treatment session,
a subject was given an eight-minute "warm-up" run in the simulator, after
which dosing began. Sixty-five minutes after the start of dosing the
subject began a 45-minute simulator run. The testing time was chosen so that
" the drug and alcohol blood levels would peak during the run. Measurements
of blood alcohol concentrationwere taken before dosing to insure an initial
0% BAC, just before and just after testing, and every hour until the BAC was
below 0.03%. Pulse rates and blood samples to determine drug levels were
also taken during these experiments but the results will be reported
elsewhere.
Apparatus: The driving simulator used in this study was developed
to test performance of control and decision skills shown to be both
critical to the driving task, and sensitive to drug effects. The
simulator design was based on a general purpose digital computer (PDP 11/60)
and associated graphics system (Megatek 7000) which provided:
* implementationof realistic vehicle dynamics
* generation of a roadway (straight, curved, etc.)
and roadway elements (signs, obstacles, other vehicles,
etc.) and
* data recording and analyses.
Detailed descriptions of the simulator are given in Michaelson et al.
(reference 5) and Allen et al (reference 6). A number of tasks were performed
during the run including curve negotiation, passing maneuvres and emergency
stops. The results reported in this paper were derived from one task, the
wind-gust control task, which was presented three times and lasted approximately
2 minutes each time. In this task the driver was required to keep the
simulator centered in the lane at a constant speed of 80 k.p.h, while being
b_,_feted by simulated wind gusts. A headina angle disturbance signal
cLnsisting of a sum of seven sine waves was used to create the wind gust effect
and allowed the derivation of car-driver transfer functions.
THEORETICAL ANALYSIS
Figure 1 shows the control loop structure which represents the driving
simulator. The driver is assumed to use heading angle (_) and lateral
position (y) inputs to steer the driving simulator. The nested Icop
structure shown, _n inner loop operating on heading angle and an outer
loop on lateral position, has been successfully fitted to data from
experienced drivers by Weir and McRuer (reference 7). By keeping the
•_ inner loop closed the driver can operate on lateral position error'with a
simple gain, i.e., corrections of lateral position may be facilitated by
_eans _f heading angle corrections. The sum of sines aisturbance, denoted
_d' contained the followina seven frequencies: 0.553, 0.916, 1.288, 2.023,
-505-
1982005792-496
2.947, 4.235 and 5.705 radians per second, i.e., the spacing was at approxiu
mately equal intervals over a logarithmic scale.
, G_(jw) and G_(jw) represent the vehicles dynamics for lateral velocity
and he_ding angle6respectively (jw is the complex frequency variable).
, In the simulator the vehicle dynamics are simulated digitally by Jifferential
equat_cns. These equations represent a mid-size American sedan dnd were
drawn from a study determinir, g vehicle dynamics of various cars by McRuer
et al. (reference 8).
Using Figure I it may be seen that the system equations can be written
as:
: Y_ G_ (n-Yyy-,) + *d
and
y = %,+ Y_S_I-_(n - Yyy- _)S
:,hereU represents the forward speed of the simulator and n, the remnan_0
that part of the driver's steering input uncorrelated with the heading an,jle
disturbance.
The next steps in the derivation of the car-driver transfer function
are:
I) substitute for lateral position, y, in the first equation using
the second equation.
2) write the equation with the effective open loop system gain,
_-_d
on the left side. The heading disturbance _d' is considered the
system inpu_ and the heading angle _.,is considered th£ output.
3) cross-correlate each side of the equation with _d to obtain
_d_-_d_d
*,!Jd_
The cross-correlation functlon _._A3w) describes the general dependence
of the headinq angle signal (_(t)) on th_ heading angle disturbance signal
(_d (t)) in terms of amplitude and phase relationships. The process of
obtaining the cross-correlation function involves converting _(t) and
Cd(t) to the frequency domain using Fast Fourier transforms. The heading
angle and heading an_le disturbance signals were recorded during the
-506-
1982005792-497
wind-gust control task at a rate of 7.5 times per second. (Analysis
;echniquesare described in detail b,,,Bendat and Piersol (reference 9).)
_ross-correlatin_ the remnant, n, with _d causes all remnant terms to
_isappear as Cmd.n=O by definition. After cross-correlation, the effective
, open loop system gain is represented by the function _d._-_d_
By definition the open loop gain equals the product of the driver transfer
function Yp a::dthe car (simulator) transfer function Yc;
that is, '_pYc= @_d_-_'_d¢ -
d
RESULTS
Obtained blood alcohol concentrations were 0.06% and 0.11% in the
diazepam-alcoholinteraction study, and 0.05% and 0.08% in the marihuana-
alcohol interaction study.
Car-driver transfer functions were calculated an(:averaged for each
roup of 15 subjects for each drug, and for each alcohol level tested
in some cases fewer subjects were available). For all drug and alcohol
treatments there were significant increases in tracking error (p<O.05).
Considering the results for each of the three drugs under the no alcohol,
or placebo alcohol condition, the largest increase in tracking error
was found for the high dose of secobarbital, the sedative hypnotic
(see table I). The increases in tracking error produced by the high doses
of diazepam (sedative tranquilizer) and marihuana were approximately
equivalent, and half that found for the secobarbital high dose.
The tracking error results for the various alcohol doses are not
as clear because different groups of subjects are being compared. Also
initial differences between groups, exacerbated by running the active alcohol
, groups some months after the placebo alcohol group had been completed, make
the alcohol results from the marihuana-alcohol interaction study less reliable
than they might be. In the diazepam-alcohol interaction study trackin_
performance under the 0.06% BAC-placebo drug condition was about the same
as under the high dose diazepam-placebo alcohol condi*_on. Tracking error
appeared to be linearly related to alcohol dose, and doubled for the 0.11%
BAC condition in comparison with the 0.06% BAC condition.
Figure 2 shows average car-driver transfer functions obtained for the
three dose levels of secobarbital. There were large drops in gain and phasL
annl_ with increasinq dose. Gain at all frequencv points, and crossover
-507-
1982005792-498
0/,,..,...
.. >,_ S..
.I-J
i.-..-
c'-
°e...-
E:_ 0
• 0
•"- 0 !
0 Ue---
_4 -,_ .i
•,w _ U
r-,q ° °
I ; °°0r- I_
U .r.- _
dk
t T .-°-_T _, 0
4-
0
r °
_ e- e- E
•,- O .,- 0
_ ""
_" >.- 0 0 _ ','
0r
T i
-508-
1982005792-499
/frequency, were significantly reduced (p<O.05). Coherence between the
heading angle disturbance and the heading angle signal was significantly
_ reduced (p<O.O01). Phase margin, which is an indicator of system stability,
was unaffected (see Table i).
The diazepam results for the placebo alcohol group are shown in Figure 2,
_ Aqain there were significant drops (p<O.05) in g_in at all frequency points
and in crossover frequency. However, the average drop in gain was less
for diazepam than for secobarbital treatment. Coherence was also significantly
reduced by the diazepam treatment.
Alcohol results for placebo diazepam condition only are shown in Figure
3. These results are not as quite clear cut as for the other drugs. Here the
lowest gains were for the 0.06% BAC alcohol condition. The effect of
alcohol was significant (p<O.05) on the gains at the second, third and fourth
frequency points only, with the Newman-Kuhls comparison of means test showing
the placebo alcohol gains to be significantly higher than for either the
0.06% or 0.11% BAC conditions. Coherence was significantly reduced by the
alcohol treatment, the greatest drop being for the 0.11% BAC condition. Mean
crossover frequency also was significantly reduced (p<O.05). (It should
be noted that the alcohol comparison was between different groups of 15
subjects while the drug comparison were based on repeated measures with
45 subjects. Thus the test of the alcohol effect was not as strong as the
, test of the drug effect.)
In summary, the results from the secobarbital,diazepam and alcohol
treatments are much the same. Gains were significantly reduced as were
crossover frequency and coherence. Phase margin was unaffected.
The effects on the car-driver transfer function for the marihuana
treatment were very different from the other drugs (see Figure3).
There were no noticeable effects on gain, crossover frequency or phase
margin. The main effect appeared to be on coherence which was significantly
reduced (p<O.05), at the high dose level only. Tracking error was also
significantly affected at the high dose only. Despite the fact that
tracking error increased the same amount for both diazepam and marihuana,
the effects on the car-driver transfer function were very different.
DISCUSSION AND CONCLUSION
The alcohol effects found in this experiment are supported by Allen
_" et al (reference 1) and Reid and Ibrahim (reference 2) who also showed
_. alcohol to reduce gains and coherence in driver transfer functions.
. Reid and Ib ahim found m rihuana to have little effect on ampl tude
or phase margin but to decrease coherence, similar to the results obtained
in this study. No comparative data are available for the secobarbital
or diazepam treatments.
i
!
1982005792-500
O_GINAL PAGE iS ".
OF POOR QjALITY
:i
_ U
°° I I,,-- _ .1¢ E O
> O oJ
o , _ ;.T
¢::: ..... /,_ c; ._ ._ .-, o c; o o (5 o o o o _ o_
•._ .,,, .._
•P _0 _0 LO r,- O (30 r._ cO o_ I'_ o'_ _ co _ o'_
L O Oq ur) _1" O'l C0 cO _ _ cO _o _ID i,D E ._
=: o _ _ .-. c; c; o o o o c:;o c; ,-- _04
•_ ._ .-, c; c; o c:;o o c:;o c; _ .,-:3
0'1 "P "_
_,1 (--) "O
'¢:E , ""
,_ ._ :3:to
._- :_ _--" "1_ _ I 0"_f,_ P" _ .k -I¢ "1¢ _ -_ ,--_ :
O ¢_._ "1= "1{ O,J
_. J=:: ._- _ 4( 4¢ • V
O '1_ • ¢M O.
L _ '==:: _ m CO _ _ ¢M _) _ _ r,,, .. O _.1,
_ >, ,_ _ r,,, _O o_ O N o_ .,=" ._" o_ _ _ o to -_
< " c; c; o c; c; o ,,, v
_T" N C_ _ID _0 _ cO cO cO _ _ t'='=l _ _1_ _ U3 0 V
•,- o ._ _ ._ o c; o c; c; c; o o c; -o
G:3 ¢'- .1¢
t,D 04 LO _ O _ ,--I _ CO O'l O CO 0 -"
_ _ c; o o o c; c; o c; c; ,, ,, o
O O .-I "r C_
,=:=: v
:_ ....... ¢=3 _....j ",r- O...._ -r = _j -r" _. _j -r- ,._ e'_v
"_ (u ..TU _,n
>' "1¢ -I¢ "1¢ _'-" --"
¢0 O. _,.
O 03 O_ _D O (_ _ _ (:3 r_ CO O'_ r", .
(_J • • • • • • •
v) - - ,- o o o (=;6 o c; o c;
•0
(3_ .J "_" n ._.1 -I- (3.. _J "r _. ..j "t-
-.J
"t_ 0 ¢" U (_ U ul
¢- "P _'- 0 E =_ ¢" 0
"0 _ S... +-) _ Vl "_ _,).r-
t 4o _ _ 0 0 _. !. e- _ _..
I
-510-
1982005792-501
-511-
1982005792-502
10 "FIGURE3. Car-DriverTransfer Functions:Marihuana,Alcohol
-- P.lacebo
---- Low Dose (mar: I00 mcg/kg B.W.
_ alc: 0.51 nKJ/kgB.W.)
n
"_X _,_ --- High Jose (mar:200 mcg/kg B.W.
5 ._ ,_,_ a,c:,.O,.,,o _..w.,
0 _. ,_arihuana _%_
o= "_ \\,X, Alcohol
A!cohol !
Log FrequencyRadians 1 I
-135 /_,_ ..._B.e'_'_
......_--- _-..._
-\ ,\
-_,__ ,_
-3|5 _ PlarlhuanA
| AlCOhOl _0
. _ :_
-512-
1982005792-503
JBoth secobarbital and diazepam act as sedatives, however, secobarbit+!
is generally prescribed at a high enough dose level that it acts as a
hypnotic (induces sleep) while diazepam's ant_-anxiety p_ope_ties become
evident when it is prescribed at a lesser dosage. Both drugs are CNS
depressants as is alcohol. In contrast to these three drugs, marihuane
is classified as a psycPedelic, i.e., affecting the thought processes.
The transfe_ function analysis clearly distinguished between these two !
classes of drugs. The analysis also discriminated the degree of sedative i
effect in that gains were reduced much more for the secobarbital treatment
than the diazepam treatment at the dose levels used in this experiment.
In addition it is interesting to note that the one drug of the four which
is supposed te mest affect thcught processes is the one whose only transfer
function effect was an increase in non linear behavior.
REFERENCES i
1. Allen, R.W.; Schwartz, S.; Stein, A.; Magdelano, R. and Hogge, J.:
The Effects of Alcohol and Marihuana on Driver Control Behavior.
Volume 1 Laboratory Simulation Experiment. Report submitted to
National Highway Traffic Safety Administration, under contract
No. DOT-HS-501257, April, 1978.
2. Reld, D.; Ibrahim. M.K.F.: The Application of Human Operator
Describing Functions to Studies on the Effects of Alcohol and
Marihuana on Human Performance. IEEE Transactions on Systems,
Man and Cybernetics, VoI.SMC-5, No.5, September, 1975.
3. Smiley, A.; LeBlanc, A.E.; French, I.W.; and Burford, R.: The
Combined Effects of Alcohol and Common Psychoactive Drugs: Field
Studies with an Instrumented Automcaile. Canadian Society of
Forensic Science Journal, Vol.8., No.2., 1975.
4. Cahalan, D.; Cisin, I.H.; and Crossley, H.M.: American Drinking
Practices, A National Study of Drinking Behavior and Attitudes.
College jnd University Press, 1969.
5. Michelson, S.; Niemann, R.; Olch R.; Smiley, A.M; and Ziedman, K.:
A Driving Simulator for Human Performance Studies Using All
Digital Techniques. Southern California Research Institute
Technical Report, January, 1979.
6. Allen, R.W.; Klein, R.H.; and Ziedman, K.: Automobile Research
Simulators: A Review and New Approach. Transportation Research
Record 706, Simulation lechnology and Traffic Accident Records
System, Transportation Research Board, National Academy of
Science, Washington, D.C., 1979.
-513-
, .-- . ( 71
1982005792-504
7. Weir, D.H.;and McRuer,D.T.: Measurementand Interpretationof Driver
SteeringBehaviorand Performance. SAE Paper No.730098,1973.
8. McRuer,D.T.; and Klein R.H.: AutomobileControllability-Drive_/
VehicleResponsefor SteeringControl. SytemsTechonology,Inc.
' Los Angeles, Submittedto NationalHighwayTrafficSafety
Administrationunder contractNo.DOT-HS-359-3-762,November,1974.
9. Bendat,J.S.; and Piersol,A.G.: RandomData:Analysisand Measurement
Procedures.Wiley-lnterscience,1971.
-514-
1982005792-505


Manual control analysis of drug effects on driving performance

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server