drivers' differential perceptions of legal and safe driving consumption

Addiction (1995) 90, 245-254

RESEARCH REPORT

Drivers' differential perceptions of legal andsafe driving consumption

IAN P. ALBERY & ANDREW GUPPY*

National Addiction Centre, University of London & *Cheltenham &" Gloucester College ofHigher Education, Cheltenham, UK

AbstractUK drink-drive countermeasures have been grounded in deterrence theory and more specifically through perse legislation. Education and information campaigns to stimulate inhibitory behavioural systems haveemphasized the legal limit in terms of "driving safeness". This study examined the relationship betweensubjective perceptions of safe driving and legal driving consumption limits and other factors important in thedecision to drive after drinking. Responses from over 900 drivers established that those who perceived safeconsumption levels to be greater than that required to break the law indicated reduced moral commitment topresent and possible future countermeasures. These drivers also had previous experience of being breath tested(but not charged with a drink-driving offence), reported comparatively lower estimates of their chances ofapprehension and accident involvement when over the legal limit, showed higher consumption levels on adriving trip and greater self-reported driving while impaired by alcohol. The implications of the findings forthe development and delivery of measures to counter drink-driving are discussed.

IntroductionWhy individuals decide to drive after excessive

-drinking has been the subject of extensive psy-chological, social and criminological research(see Albery, 1991). Such diversity of research,however, has not resulted in an all-encotnpassingsystetn of countermeasures which reliably ad-dresses the probletn of driving while intoxicated.Instead the majority of attempts to decreasedrink-driving behaviour has relied almost exclu-sively on a model of general deterrence. Thistheory proposes that for an intervention to pro-vide the mechanisms for conforming behaviour itis required that apprehension and punishment

Ian P. Albery, Addiction Research Unit, National AddictionCentre, 4 Windsor Walk, London SE5 8AF; and Andrew Guppy,Faculty of Business and Social Studies, Francis Close Hall,Cheltenham and Gloucester College of Higher Education,Cheltenham, Gloucester GL50 4AZ, UK. Correspondence toIan P. Albery.

for a contravened behaviour be certain, severeand delivered swiftly (Paternoster et al., 1982;Grasmick & Bryjak, 1980). It is argued thatrepeated exposure to such processes, either viapersonal experience and/or education/infor-mation programmes, acts to reinforce the deter-rence processes such that beliefs of certainty,severity and celerity as consequences of commit-ting an act become internalized and subsequentoffending behaviour inhibited (Andenaes, 1977;Grasmick & Green, 1980). Research has, how-ever, consistently shown that when isolated forstudy within the general driving population cer-tainty and celerity of punishment remain import-ant inhibitors of behaviour, whereas severity ofpunishment (e.g. imprisonment, heavy fines) isless influential (see Ross, 1992 for review;Homel, 1988).

Central to the deterrence-based policies

0965-2140/95/020245-10 © 1995, Society for the Study of Addiction to Alcoholand other Drugs

246 Ian P. Albery & Andrew Guppy

adopted by many countries is per se legislation(Ross, 1984). The setting of such legal limits isassumed to create an environment in which pun-ishment is perceived to be more certain andenacted with greater speed, thus providing abasis for the operation of deterrence-type pro-cesses. Historically, such laws specify bloodalcohol concentration (BAC) levels which are acompromise figure intended to reflect both thepoint at which a driver becomes significantlymore likely to be accident-involved than a com-parative driver with a zero BAC and that whichis politically acceptable, but falls within the BACregion of increased accident liability. As such,there is large cross-national variation in legalBAC limits (e.g. 100 mg/100 ml in Eire andmost US states; 80 mg/100 ml in the UK,Canada, and France; 50 mg/100 ml in Belgiumand the Netherlands and 20 mg/100 ml inSweden).

It is clear that per se legislation assumes anassociation between unlawful BAC levels andthose deemed unsafe for driving in terms ofcomparative risk of accident involvement andinjury between impaired driver and sober driver.In terms of the deterrence model, whether anindividual's driving performance is impaired ornot after consuming a given amount of alcohol isnot important. For deterrence to operate or failto operate the crucial factor influential in thedriver's decision to drive after drinking is a per-ceptual one. In other words, for a person torefrain firom driving after drinking (s)he must atleast demonstrate moral attachment to the per selaw (Andenaes, 1977; Snortum, Berger &Hauge, 1988). In this way an individual hassome conception that statute law is not designedto be harmful to the individual; rather that theadoption of a particular statute will protect theindividual from harm and in fact may havebenefits (e.g. remove the increased risk of acci-dent involvement when impaired). As such theindividual values the utility of a specific law andconforms appropriately.

Previous research has identified an associationbetween reported drink-driving behaviour andestimates of personal drinking that would exceedthe legal limit (Guppy, 1988). However, drink-driving behaviour and its correlates have notbeen examined closely with respect to the rela-tive distance between perceptions of legal limitconsumption, and those consumption levels sub-jectively deemed to be unsafe for driving. It is

felt that this may provide further insight con-cerning the role moral attachment has in supple-menting the usual deterrence components ininfiuencing the decision to drink and drive. Thiswould necessarily have implications for the de-velopment and evaluation of present deterrence-based counter-measures in a number ofcountries.

MethodSubjects and procedureSubjects were derived from a self-report ques-tionnaire survey distributed by post to 2300 fullUK driver's licence holders. Names and ad-dresses of potential respondents were drawn atrandom from a data base holding a representa-tive sample of driving licence information for theUK. To maximize representativeness of the po-tential sample drawn to the actual driving popu-lation, random sampling stratified by sex wasutilized. In this way, out of every 100 casessampled 60 were men and 40 women; a ratiorepresentative of the actual UK driving popu-lation. Each subject was sent one covering letter,one questionnaire and a FREEPOST return en-velope. To offset the possible confounding ef-fects of subjects merely reporting sociallydesirable responses, an explicit guarantee for theanonymity of subjects was made. The survey wasundertaken during the autumn and winter of1990.

Of the total number distributed 1172 com-pleted questionnaires were returned, giving asimple response rate of 51%. The actual re-sponse rate may well have been higher but for asmall number of returns stating that the individ-ual was no longer at that address. Of the totalnumber of responses, however, 161 (13.7%) re-ported that they did not consume alcohol at all.As such they were removed from subsequentanalyses making a total of 1011 respondents. Forsubsequent analyses, fiuctuations in this samplesize is due to the omission of responses by sub-jects. The mean age for the sample was 36.35years (range = 17-80 years), and was comprisedof 596 males and 413 females. Drivers had heldfliU driving licences for a median of 180 months(range = 5-756 months).

MaterialsA self-completion type questionnaire was utilized

Legal and safe driving consumption 247

to derive the data for the study. Demographicinformation concerning the subject's age, sex,driving experience (measured in months elapsedsince a full licence was attained) and drivingexposure (measured by average annual mileage)was requested. Other responses utilized in thepresent report were designed to address the fol-lowing.

1. Perceptions of drink-driving consumption lev-els. Subjects were asked to estimate the maxi-mum amount of alcohol they could drink anddrive and remain (a) safe to drive and (b) belowthe legal limit. Responses were converted intounit consumption estimates (e.g. 1 pint normalstrength beer equals 2 units, single spirit equals 1unit, etc.)

2. Deterrence items. These were adopted to testthe perceived likelihood of drink-driving relatedfuture events. A series of vignettes were pre-sented. Subjects were asked to imagine themselvesas the subject of each vignette. The presentedvignettes were as follows: imagine that you havebeen drinking in a pub in the evening and areabout to drive home. You have had enoughalcohol to take you just above the legal limit.What do you think the chances are that you will:(a) have an accident on your journey; and (b) becaught by the police for drinking and driving. Asecond vignette was presented identical to thefirst except that on the occasion to be imaginedthe subject was sober. They were also asked toestimate on a seven-point logarithmic scale(Guppy, 1993) their personal chances of (a)being caught when just above the legal limit, (b)being accident-involved when just above the le-gal limit and (c) being accident involved whensober. Points on the scale were labelled 1/1,1/10, 1/100, 1/1000, 1/10 000, 1/100 000 and1/1 000 000, and were scored fi-om 0 to 6 re-spectively. By subsequently taking the anti-loga-rithmic value of the response recorded meanlikelihood estimates can be calculated, such thata mean of 3.5 is equivalent to a perceived chanceestimate of 1/3162.

3. Exposure to the consequences of driving whileimpaired. Subjects were asked whether they hadbeen (a) breath tested, (b) charged v«th drink-driving and (c) been involved in an alcohol-re-lated accident in the past. Whether subjects

knew somebody else who had been breath tested,charged or involved in an alcohol-related acci-dent was also ascertained.

4. Moral attachment items. To measure thevalue individuals attribute to measures designedto prevent or dissuade driving while impaired, ormoral attachment, and whether potential attach-ment is generalized to subjective perceptions ofthe introduction of other interventions (e.g. ran-dom breath testing), 11 attitude statements werepresented to the subjects. Subjects were asked tomark the point on a Likert type scale whichcorresponded to how far they agreed or dis-agreed with each of the statements. Points on thescale were marked "strongly agree", "agree","neither agree nor disagree", "disagree" and"strongly disagree". Scores for each statementranged fi^om one to five, high scores reflectinggreater moral attachment or anti-drink-drivingattitude. For the sake of brevity items are la-belled ATTl to ATTll. Subsequent presen-tation of results utilizes these labels. The 11statements were as follows:

• Present drink-driving laws are too lenient andshould be made more severe (ATTl).

• Convicted drink-drivers should be allowed apartial driving licence for working purposes(ATT2).

• It is not enough for publicity campaigns to berun just over Christmas. They should be usedthroughout the year (ATT3).

• The only effective way to punish drink-driversis to imprison them (Al'1'4).

• Alcoholic prices should be increased and non-alcoholic drink prices decreased to curb drink-driving (ATT5).

• The extended opening hours legislation intro-duced in 1988 only encourages people to drinkand drive (ATT6).

• More publicity campaigns regarding the con-sequences of combining driving with drinkingwould stop people from drink-driving(ATT7).

• Random breath testing is the best way to deterdrinkers from driving (ATT8).

• The legal limit for inexperienced driversshould be lower than for experienced drivers(ATT9).

• Random breath testing would be a threat topeople's civil liberties (ATTIO).


• I would not drink and drive if I knew that thepolice could perform random breath tests(ATTll).

5. Drink-driving behaviour. Subjects wereasked to mark on a seven-point scale how oftenduring the past 12 months they had driven whenthey thought they were over the legal limit. Sub-jects selected one of the following responsepoints to indicate their behaviour: "never","once or twice", "3 to 5 times", "6 to 10 times","once a month", "once a week" and "more oftenthan once a week", scored zero to six, respect-ively. A further question asked subjects to reporthow much alcohol they had had to drink on thelast occasion they had a drink away from homeand subsequently drove. Responses were re-coded into unit estimates in accordance with theprocedure highlighted previously.

ResidtsFor all analyses responses made to the maximumamount an individual could drink and still bebelow the legal limit equal to 0 units are ex-cluded. This is because it must be assumed thatpeople in general are aware that they can drinksome level of alcohol with respect to the legallimit. A response of zero may, therefore, refiectmore of an attitude that no alcohol should bedrunk before driving rather than an accurateassessment of their perceived consumption.

Legal and safe driving consumption limitsIn general mean consumption estimates for thelegal limit were larger than for safe consumptionlimits, 2.97 units (SD 1.47, range 1-10) versus2.76 (SD 2.34, range 1-18) units, respectively.This difference was found to be significant(r(864) = 3.12, p < =0.01). Males reportedsignificantly greater legal limit estimates thanfemales (means 3.52 and 2.10 units, respect-ively), t(861) = - 15.56, /)<0.001. Male driversalso reported significantly greater safe drivingconsumption limits than females (means 3.45and 1.68 units, respectively), r(861) = -11.62,p < 0.001. Estimates for both consumption itemsdid not differ across the age groups 17-25 years,26—45 years and those older than 44 years(p = 0.5203).

Differential legal and safe driving consumption esti-matesTo test mean differences between legal and safedriving consuniption estimates, differentialscores for each individual were calculated bysubtracting perceived safe driving consumptionestimates from legal driving consumption esti-mates. In this way negative figures correspond toresponses in which perceived safe limits aregreater than legal estimates (capable > legal driv-ers), positive values to perceived safe limits lessthan legal levels (legal > capable drivers), whilevalues approximating zero correspond to a per-ception of no difference between safe and legaldriving estimates (capable = legal drivers). In thisway difference scores ranged from — 16 to 8with a mean of 0.175 and mode of 0.

To enable comparisons between those subjectswho (a) perceived safe driving levels to be greaterthan legal levels, (b) those who perceived safedriving levels to be less than legal limits and (c)those where no differential was apparent for safeversus legal consumption, individuals with nega-tive difference scores (i.e. — 1 or below) werecategorized into one group, those with positivescores (i.e. + 1 or above) into a second groupand those with scores of zero into a third group.On this basis the three groups comprised 188(22%), 284 (33%) and 393 (45%) individuals,respectively. This group factor formed the inde-pendent measure for subsequent analyses.

Demographic factors. Age was found to differacross groups, F(2,922) = 10.9, p<0.001. Posthoc analyses show that subjects reporting greaterand reduced estimates for safe levels in compari-son to legal levels (means 39.36 and 39.61 years)were significantly older than those individualsreporting no bias (mean 34.93, p<0.05). Sexwas also found to be significantly associated withdifferential consumption status, x^ (2) = 17.51,/)< 0.001. Females were shown to be under-rep-resented in the group of subjects reportinggreater safe consumption levels compared to le-gal limits. All other cell residuals were small.

Deterrence effects. Mean perceived chances ofaccident involvement when over the legal limit(i.e. impaired) differed significantly across safe/legal consumption groups, F(2,843) = 33.51,p < 0.001 (Table 1). Post hoc tests show that the'capable > legal' respondents believed their likeli-hood of being accident involved after drinking in


Table 1. Mean perceived chances of apprehension and accident involve-ment when impaired by alcohol and likelihood of accident involvement when

sober across safe and legal limit consumption differential groups

Condition

Capable > legalMeanSDn

Legal > capableMeanSDn

Capable = legalMeanSDn

Sample totalMeanSDn

Apprehension'

1/4509°1.45185

1/1706°1.62276

1/21801.47387

1/23581.52848

Variable

Impairedaccident*

1/5300''1.42185

1/403*'1.43276

1/1643''1.51385

1/13411.52846

Soberaccident

1/462271.31185

1/394821.31280

1/505361.30388

1/457091.30853

* = Significant between-subjects effect, p < 0.01."''' = Means show significant post hoc group differences, p < 0.05.

excess to be significantly less than 'capa-ble = legal' and 'legal > capable' drivers(p<0.05). Moreover, 'legal > capable' driversperceive their chances of accident to besignificantly greater than drivers who believe thattheir safe and legal limits are equal (p<0.05).

Mean differences between groups are also ap-parent for perceived chances of apprehensionwhen impaired by alcohol, i^(2,845) = 4.49,p<O.Ol. Further analysis shows that comparedto 'legal > capable' subjects, 'capable > legal'drivers believe the likelihood of personal appre-hension on a drink-driving trip to be significantlyless (p<0.05. Table 1). All other mean differ-ences were not significant. On average driversperceived the chances of accident involvementwhen sober to be approximately 1/45 709. Nobetween-group differences were shown,F(2,850) = 0.577, p > 0.05 (Table 1).

Exposure to the consequences of driving whileimpaired. Results show a significant associationbetween whether an individual has been breath

tested in the past and safe/legal consumptionestimates, x^ (2) = 13.19, p<Q.Ol. Residualanalysis shows those subjects who reported beingbreath tested in the past are over-represented inthe 'capable > legal' group. In addition, 'le-gal > capable' drivers are under-representedamong those breath tested, whereas the residualfor the 'capable = legal' group was negligible.

Knowing somebody else who has been breathtested in the past is also shown to be associatedwith whether an individual displays a safe/legalconsumption estimate discrepancy, y^ (2) = 9.31,p<O.Ol. The 'capable>legal' subjects are over-represented among those who know somebodyelse previously breath tested, while those in the'legal > capable' group are under-represented inthe distribution. Variables describing being per-sonally charged with drink-driving or knowingsomeone who has been charged, and being per-sonally involved in an alcohol-related accident orknowing someone else accident involved, werenot shown to be associated with safe/legal con-sumption biases (p>0.05).


Moral attachment. Table 2 presents resultsfrom mean difference analyses for the items de-signed to measure moral attachment to drink-drive countermeasures and other driving whileimpaired attitudes related to interventions. It isclear that with the exception of two statements("More publicity campaigns regarding the conse-quences of combining driving with drinkingwould stop people from drink-driving (Al l7)"and "[T]he legal limit for inexperienced driversshould be lower than for experienced drivers(ATT9)".), the 'capable > legal' subjects reportattitudes which show less moral attachment tolegislative and socially driven countermeasureinitiatives.

Relative to the other two groups 'capable >legal' respondents:

(1) Disagree that present drink-driving laws aretoo lenient (ATTl), F(2,858) = 26.81,p<0.001.

(2) Agree that convicted drink-drivers should beallowed a drivers's licence for work purposes(ATT2), F(2,858) = 15.12,/)<0.001.

(3) Disagree that publicity campaigns should berun throughout the year (ATT3),F(2,859) = 10.18, p<0.001.

(4) Disagree that the only effective way to pun-ish drinking drivers is to imprison them(ATT4), F(2,859) = 3.94, p< 0.01.

(5) Disagree that alcohol prices should be in-creased to curb driving while impaired(ATT5), F(2,859) = 8.01, p< 0.001.

(6) Disagree that the UK extended openinghours legislation introduced in 1988 encour-ages drivers to drink more (ATT6),F(2,859) = 7.85, p < 0.001.

(7) Disagree that random breath testing (RBT)is the best way to deter drinkers from driving(ATT8), F(2,859) = 10.25, p<0.001.

(8) Agree that RBT would be threat to people'scivil liberties (ATTIO), F(2,860) = 16.87,

(9) Disagree that they personally would notdrink and drive if they knew that the policecould perform RBTs (ATTll),F(2,853) = 14.42, p<0.001.

Furthermore, for two items (ATTl and ATT2)drivers who reported legal estimates to be greaterthan safe estimates (legal > capable) showedgreater moral attachment than those subjectswho thought legal and safe limits to be equal(p<0.05). The trend appears to be for those

individuals who perceive greater safe than legallimits to recognize least value in legislative andsocial measures, followed by 'capable = safe'subjects, while 'legal > capable' drivers showattitudes indicative of greatest moral attachment.

Legal and safe consumption estimates and actualdriving behaviour. Initial analysis showed that thedistribution of scores across all subjects withrespect to frequency of self-perceived drivingwhile impaired was significantly positivelyskewed (2=38.74, p<0.05); 76.6% of subjectsreported never drink-driving during the previous12 months while 20.3% had driven impaired onat least one occasion. As such, this variable wascollapsed into two discrete categories; "never"and "at least once or twice" driven while im-paired. Analysis of the independence of safe/legalconsumpdon bias and drink-driving frequencyshows significant association between the distri-butions, x^ (2) = 74.06, p < 0.001. Observed/ex-pected residuals show 'capable > legal' drivers tobe over represented among drivers repordng hav-ing driven while impaired. In contrast, 'le-gal > capable' subjects were found to beunder-represented among drinking drivers, whileresiduals were of minimal magnitude for 'capa-ble = legal drivers'.

Groups were also shown to differ significandyin mean alcohol consumption estimates on theirlast drink-driving occasions, F(2,701) = 20.58,/)< 0.001 (Table 3). Means for all groups dif-fered significandy. 'Capable > legal' subjects re-ported drinking greatest quantities of alcohol ontheir last driving trip, followed by those subjectswho perceived equal safe/legal estimates, with'legal > capable' individuals reporting least con-sumption (p<0.05).

DiscussionLegal and safe driving consumption estimatesIn general, subjects were found to perceive legalconsumption limits to be greater than theamount they could drink and still remain fit todrive. What is noticeable, however, is that themean figure reported for both legal and safedriving is less than 3 units. Previous research byGuppy (1988) on a sample excluding femalesrevealed mean estimates of the legal limit ofmore than 5 units. Similarly, given that previousresearch (e.g. Cameron & Donkin, 1977) hasidentified that approximately 5-7 units is likely


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Table 3. Mean alcohol consumption (units) before lastdrink-drive trip across safe and legal limit consumption

differential groups

Condition

Capable > legalMeanSDn

Legal > capableMeanSDn

Capable = legalMeanSDn

Sample totalMeanSDn

VariableAlcohol consumption (units)*

4 60''3.47168

2.89''2.56197

3.15''2.48339

3.412.85704

* = Main between-subjects effect, p < 0.01 .^'^ = Meansshow significant post hoc group differences, p < 0.05.

to be the most reasonably accurate estimate ofthe legal limit in terms of consumption, it isobvious that some large disparity exists betweenconsumption levels perceived subjectively tocontravene the legal limit and reality. In otherwords, it is clear that on average sample respon-dents underestimate consumption levels requiredto bring them to the legal limit by as much ashalf. Indeed, it is found that only 4% of thesample estimated 5 or more units to be the legaldefinition. Such findings are consistent for thegender of an individual. Although males con-sidered legal limits to be significantly larger thanfemales, all estimations remained far below 5units. The difference found between males andfemales is not unexpected. It has been shownthat females register greater BACs after consum-ing equivalent amounts of alcohol than males(e.g. Stein, 1986). If females are aware of thisphenomenon one would expect theni to report,on average, lower legal consumption levels.

Such general findings are encouraging. Ifdriver education has been efficient in emphasiz-ing that even at the legal limit safe driving issignificantly impaired, one would expect safedriving estimates to be lower than legal percep-tions. Although this result informs us that onaverage the safe/legal difference is in the desired

direction (i.e. no difference or legal consumptiongreater than safe), it does not show whethersignificant proportions or groups of drivers donot conform to the consensus.

Differential consumption estimatesTo identify groups of drivers who appear not tohave been persuaded by the 'safe equals legal'message, or who have not been exposed to edu-cation, safe/legal differential estimates were suc-cessfully developed. In this way responses madeto legal and safe driving limits, and the differencebetween them, allowed for the cross-sectionalidentification of three distinct groups of drivers.Thus, drivers who perceived safe driving levels tobe greater thari legal limits, those who felt thereto be no safe/legal difference and finally a groupwho perceived legal estimates to be greater thansafe limits were identified. It is clear that it is thefirst group which has not been receptive to thelegal equals safe phenomenon. To compare thesedrivers with other safe/legal group clusters interms of demographic items along with thosevariables found previously to be important in thedecision to drink and drive, highlighted import-ant typographic and perceptual information.

Demographics. It was shown that those driversreporting greater safe estimates than legal onestended to be older than drivers who reported nobias, but not older than those drivers who per-ceived legal estimates to be greater than safelevels. This may point to the idea that educationwith respect to the impairing effects of alcoholand its relationship to the legal limit should befocused more at an older population. Thefinding that male drivers constitute a significantproportion of the 'capable > legal' group indi-cates that education and information should alsobe directed more at male drivers.

Deterrence issues. The finding that 'capa-ble > legal' drivers estimate their personal likeli-hood of being apprehended for driving whileintoxicated to be significantly less than otherdrivers may be interpreted in a number of ways.One explanation may be that the present systemof measures designed to deter these drivers fromdrinking is not achieving its inhibitory be-havioural effects. Indeed, all drivers perceived


their chances of apprehension to be below thefigure reported by a sample of male drivers in theUK. Guppy (1984) reported that a subjectivechance probability of apprehension in the regionof one in 32 trips would be required to preventthese male drivers from driving while impaired inthe future. Such findings are also supported bythe evidence that 'capable > legal' drivers per-ceive their chances of accident involvement whenimpaired to be less than other drivers. The linkbetween alcohol consumption and accidentlikelihood does not appear to have been recog-nized by this group of drivers.

An alternative explanation could be that 'capa-ble > legal' drivers have learned through re-peated exposure to drink-driving trips in whichthey are neither accident-involved nor apprehen-ded, that subjective likelihood of experiencingthe more negative consequences of driving whileimpaired are indeed lower than would be as-sumed by other drivers, particularly 'le-gal > capable' drivers. Indeed, it was shown thathaving personally been breath tested or knowingsomebody else who has been is associated withthose drivers who perceive safe limits to out-weigh legal limits. Because it was also establishedthat being charged with drink-driving is not asso-ciated with safe/legal estimates, it follows thatbeing breath tested and not charged may encour-age higher estimates of both safe and legal limits.Moreover, instead of creating a perception ofdeterrence from drinking before driving the ef-fect may be to prompt future offending behav-iour. Indeed, it was established that drivers withlarger safe, as opposed to legal, estimates reportmore actual drink-driving behaviour occasionsthan other drivers, and also greater estimates ofunits of alcohol consumed on their last awayfrom home drink-driving trip.

For deterrence to be effective the individualshould value a deterrence-based law (e.g. per selegislation) or be morally committed to the law(Snortum, Berger & Hauge, 1988; Andenaes,1977). A lack of commitment to drink drivelegislation and other socially driven measuresmay to some extent explain both safe/legal con-sumption discrepancies and the observed differ-ences between groups of drivers in terms ofperceived chances of apprehension when overthe legal limit and perceived likelihood of acci-dent involvement when impaired. More recentlyit has been argued that deterrence-related per-ceptions are not independent from other norma-

tive beliefs that individuals hold about differentissues (Karstedt, 1991). Individuals who tend tocontravene specific legal thresholds may also givelower estimates of likelihood of apprehensionand accident involvement when impaired. Simi-larly, Problem Behaviour Theory Qessor, 1987)would predict that driving while intoxicated, andits related system of attitudinal and belief struc-tures, is not an uncharacteristic behaviour for theindividual; rather, that it is just one of a numberof problem behaviours performed, each with anunderlying set of beliefs contributing to an over-all normative system of perceptions. It was con-sistently shown that drivers with a greater safethan legal consumption bias held a more pro-drink-driving perspective and were less morallycommitted to present laws and the introductionof new initiatives to curb drink-driving behaviour(e.g. RBT, taxation increases, lower legal limits,etc.). If deterrence theory is correct and individ-uals are only inhibited fi-om behaving in an of-fending manner if they are in some way morallycommitted to a law, the results would indicatethat 'capable > legal' drivers would fail to bedeterred by new legislation. This argument,however, is not necessarily valid since the threatof new enforcement and the implementation ofnew enforcement procedures (e.g. RBT, lowerlegal limits) may operate in distinct ways onactual deterrence. This issue can only be ad-dressed by the controlled evaluation of the intro-duction of a novel countermeasure.

ConclusionsTo study safe/legal discrepancies has proved it-self important for a number of reasons. First, toidentify distinct groups who appear not to recog-nize education about the impairing effects ofalcohol, and undertake typographic analysis ofthese groups, will enable initiatives to counterdriving while intoxicated to be focused moreappropriately. Secondly, by studying the distinctresponses made by such groups to items deemedimportant in the decision to drink and drive (e.g.moral attachment, deterrence issues, etc.) hashighlighted that different countermeasures maybe required for different safe/legal consumptiongroups. Finally, one possible utility of the cate-gorization of the drivers according to safe andlegal consumption estimates may be that itproves a reliable surrogate measure of offendingor non-offending drink-driving behaviour.


AcknowledgementWe would like to express our thanks to CranfieldUniversity for funding this research.

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