Working conditions and fatigue among lorry drivers : Alcohol, drugs and driving safety : a literature study

Transcription

1 Working conditions and fatigue among lorry drivers : Alcohol, drugs and driving safety : a literature study M ichel V allet, Salah K hardi IN R E T S-L E N - case Bron C edex France IN T R O D U C T IO N T he very specific w orking and living conditions o f truck drivers affect their driving and road safety in general. Surveys and results published in the literature are not alw ays very convincing and are often discrete about the im pact o f alcohol and drugs on accidents. N evertheless this body o f literature m erits detailed exam ination as it can help to identify and ascribe values to the part played by these different factors in accident risks. Som e statistics underline the high im plication o f trucks in accidents. 3% o f all the autom obiles in the U SA are trucks (D ot 1995) and these account fo r 7% o f all the m iles driven and 11% o f all fatal accidents. T his involvem ent rate w as observed for the period (D O T-N H TSA 1994) and it w as also noted that fatigue is a m uch higher factor in accidents involving trucks than in accidents involving cars alone. T he ratio is 1 to 7. W alsleben (1994), in a general survey on the im pact o f sleepiness at the w heel on professional drivers, also notes the high increase in accident risks. In France, P. B otto used the N ational Accident O bservatory (SIA congress 1995) to exam ine 600 accidents involving trucks and coaches, and found the follow ing statistics - trucks vs. cars: 48%, trucks vs. trucks o r trucks alone : 35%, trucks vs. o th er vehicles : 17% 9% o f all accidents involve trucks. L ack o f concentration is a frequent cause w hen a truck ru n s into the back o f a track it is follow ing. This type o f accident accounts for 53% o f track to track collisions - and only 7% w hen the vehicle in front is a car. T his m eans that the basic reason is not only lack o f concentration. The long queues o f trucks w hich build up on m otorw ays is one o f the main reasons for this type o f accident. 57% o f coach accidents occur at night and 70% betw een 1 a.m. and 8 a.m.. 50% o f all accidents occu r at w eekends. In a survey carried out in the U nited K ingdom on a sam ple o f 9000 people, M aycock (1995) exam ined the sub-group o f professional drivers. In this B ritish T R L report, the survey on long distance drivers concern track drivers, aged betw een 20 and 60, driving on average 115,000 km p er year, 2/3rds o f w hich w ere on a m otorw ay. 205 drivers stated that they had had 252 accidents over a 3-year period :

2 - there is no relationship betw een the frequency o f accidents and the total num ber o f kilom etres driven nor the num ber o f kilom etres driven on m otorw ays, - accident frequency is strongly linked to age : 0.44 accidents in 3 years for the 17 to 29 year age group and 0.3 accidents for the 55 and over age group (these figures w ere identical in the global survey from which the sub-group was taken), - 37% o f the drivers snored at night, w ere over-w eight (m easured at the neck) and felt sleepy during the daytim e. T his group are twice as likely to have an accident than those w ho do not suffer from sleepiness (Epw orth scale). The author believes that this observation should be exam ined by further research. W y c k o ffin th e U SA and the R egular Com m on C arrier Conference in its longitudinal study in Florida, (w orks reported by H aw orth 1991) found a low er accident risk rate than the TRC survey. On average, drivers have their first accident after 7 years driving ; but experienced drivers have few er accidents than novices. O uverkerk, in the N etherlands (1988) reported that in , 16% o f 650 truck drivers had had a traffic accident. Living conditions have changed significantly since the first French study, published in the first num ber o f the review, "Le Travail H um ain" (Lahy 1937) - quoted by H am elin and even since the review by M acd onald in Lahy described the epic conditions o f truck drivers as follow s: "Au cours de notre enquete nous nous som m es rendus com pte que ces hom m es, qui tous aim ent leur m etier et ne voudraient pas en prendre un autre, eprouvent une grande fatigue pour accom plir leur travail. Us disent que cette im pression com m ence le soir apres le depart de X (soit apres 1 2 heures de voyage environ)... et c'est au petit jo u r que les accidents se produisent le plus so u v e n t; ils eprouvent des troubles d'ordre sensoriel, particulierem ent visuel ou tactile. Ils nous ont decrit des cas d'hallucinations hypnagogiques. A insi, ils ont la sensation d 'av o ir les yeux ouverts et de voir la route devant eux, m ais leurs m ains ne sentent plus le volant et ils n'entendent plus le ronflem ent du m oteur. L 'un d'eux racontait qu'il lui arrive parfois de s'arreter et de descendre au milieu de la route afin de s'assurer q u'elle est assez large pour perm ettre au cam ion de passer. The logical sequence accepted in the past used to be "the study o f the w orking conditions o f truck drivers, o f fatigue and then o f the risks that they can engender" (H am elin 1994). This has now changed due to the dem onstration o f several factors. These new dim ensions - alcohol, m edication and narcotics as well as natural o r pathological m odifications to biorhythm s and vigilance are not a priori induced by w orking conditions or fatigue. If the problem is analysed accurately w ith these notions in m ind, it can be adm itted that som e o f these factors are m ore or less linked to w orking conditions and that they can contribute to the risk factors exam ined in d e ta il: the use stim ulants is an exam ple

3 T R U C K D R IV E R S A N D A L C O H O L In the m id 1980s, C hiron reported that doctors specialising in w orkplace m edecine estim ated that 10% o f truck drivers drank to excess (i.e. had becom e chronic alcoholics), vs. 7.4% in a the overall population and 10.4% in control-group w orkers : "It is am azing to find m ore excessive drinkers driving trucks than in other jobs!". R egulations concerning blood alcohol content and the efforts o f com panies, including m otorw ay operators, to reduce and even prevent driving after the consum ption o f alcohol have certainly been extrem ely effective. In fact, in a recent survey by IN R E TS (B iecheler 1994) alcohol w as detected in 19.2% o f 714 drivers: 15.1% with under 0.24 mg/1, 2.4% with 0.25 to 0.39 mg/1 and 1.7% w ith over 0.4 mg/1 o f alcohol. Curiously, one driver in four exceeds speed lim its in the group w hich has only drunk small or m oderate am ount o f alcohol vs. 17% am ong sober drivers and those drivers w ho have drunk m ore than the lim it. T he survey reveal that am ong truck drivers (3.9% o f the total sam ple) 6.9% had a level o f blood alcohol o f over 0.25 mg/1 and 0.8% drove over the speed lim its w hereas am ong other professional road users (5.4% o f the total), there w ere 0% w ith a blood alcohol rate o f over 0.25 mg/1 but 8.7% w ere breaking the speed lim its. Few results have been published about truck accidents and alcohol. Sum m ala (1994) found that Finnish truck drivers are very sober and resist fatigue better than car drivers. Alcohol usage does appear in other studies detailing the proportion o f drivers involved in accidents and their blood alcohol rates. H aw orth (1989) studied the part played by fatigue in truck accidents in A ustralia by analysing judgem ents in law courts follow ing in-depth review s of each accident. The factors exam ined reveal that accidents were caused by: inattention 25.3 clum sy driving 9.1 fatigue 9.1 on the w rong side o f the road 15.1 speed difficulty w ith rem aining on the pavem ent alcohol 14 driving after taking m edication 3.2 suicide 4.8 other factors 26.9 A s the total adds up to m ore than 100, this m eans that several hum an factors contribute to the accidents sim ultaneously. In France, M ontastruc (1988) exam ined the results o f biological blood assays (executed in the hospitals w here people involved in accidents w ere taken - and therefore not only truck drivers) and found that 38% o f all people involved in accidents had been drinking alcohol, and had som etim es taken narcotics too. 22% o f the 570 casualties had been taking m edication o f som e sort

4 N A R C O T IC S, M E D IC A T IO N A N D S T IM U L A N T S U S E D B Y T R U C K D R IV E R S The potential danger from the effect o f m edication and narcotics on driving vigilance preoccupies public authorities and as G. Lagier states (1955) this subject is now included in driving tests. French drivers use tranquillisers to a great extent - 15% in the +15 age group, 30% o f w hom are chronic users vs. 6.7% in C anada w hich m akes France the 7th biggest user out o f 45 nations. O n-going studies com paring drivers taking sedatives involved in accidents w ith drivers w ho have not had accidents show a rate o f 5 to 10% and even higher. The percentage is also approxim ately 5 to 10% for narcotics usage in hospitalised drivers. T his latter observation is confirm ed by non-m andatory tests w hich a m ajor com pany recom m ends its drivers take during norm al controls by w orkplace doctors. Lagier underlines the difficulty o f establishing the im pact o f narcotics on accidents. The analysis o f police reports on drivers arrested for "apparent drunkin driving" show s a very high percentage o f low or zero alcohol rates. M edication and/or narcotics are m ore responsible for the states o f stupor. L agier states that these effects are due to m any causes: - over-doses o f m edication, - non-specific effects, particularly at the start o f treatm ents, - very rare but non-foreseeable effects, - severance effects, - interaction with other m edication, - interaction with alcohol. In these 2 latter cases the com bined effects are m ultiplied. T o this should be added problem s w ith vision created by som e m edications - particularly antidepressants. Three categories o f substances are considered to counter sleepiness (Roussel 1995): - caffeine m aintains aw areness and perform ance but its effect is fleeting and can lead to undesirable secondary effects due to the rapid reduction in its efficacy w hich encourages users to take higher and higher doses. From 200 to 400 m g (2 to 4 cups), caffeine can cause stress, agitation and even excessive blood pressure, am phetam ines have a rem arkable pow er for keeping people aw ake. T his w as confirm ed many times during the W orld W ar II. A m phetam ines are used by athletes as dope and are a true narcotic (tolerance increases as doses rise, leading to physical and psychic dependence, w ith a severance syndrom e and high product need)

5 Secondary effects are dram atic on the cardio-vascular system (high blood pressure and tachycardia), the gastro-intestinal system (nausea, vom iting) and especially in the neuropsychiatric area (with progression towards delirium ), - eugregorics, the m ost efficacious o f w hich is M odafinil, are as pow erful as am phetam ines for m aintaining aw areness, despite an extrem ely different biochem ical m echanism. T he absence o f m ajor secondary effects and addiction m ake them the ideal m olecules for fighting sleep disorders but no attem pt has been m ade to m ake their use w idespread. H om e (1995) used a sim ulator to study the stim ulant role o f caffeine in coffee, tea o r chocolate. It is efficacious on fatigued drivers but has very little effect on drivers w ho are fully aw ake. The results appear to be convincing. In the Florida study (1989), it is interesting to note that all the drivers questioned thought that 25% o f their colleagues regularly drove under the influence o f narcotics. To obtain objective results L und (1988) carried out analyses w hich revealed, fo r 317 cases : cannabis : 15%, non prescribed stim u la n ts: 12%, prescribed stim ulants : 5%, cocaine : 2% and a lc o h o l: 1%. T R U C K D R IV E R S W O R K D U R A T IO N, S L E E P D E P R IV A T IO N A N D F A T IG U E In 1993, truck drivers in France w orked from 49 hours per w eek (with a daily return to their com panies) to 62 hours per w eek for four-day trips (H am elin 1996). The num ber o f hours w orked p er w eek had not changed since The time during w hich drivers effectively drive varied from 28 to 42 hours. H am elin (1990) established a risk level depending on the am plitude o f the w ork, the proportion o f the jo b com pleted at night-tim e and the driv er's com pany category. T he risk o f being involved in a corporal accident, at a given m om ent, is the quotient o f the num ber o f accidents at that m om ent and the num ber o f drivers exposed at that instant. F rom this calculation is appears that the risk factor fo r ow ner-drivers is multiplied by 3, particularly w hen driving at night. It w as also observed that the risk factor increases to 2.5 in the m iddle o f the night and to 1.7 when drivers w ork m ore than 1 1 hours per day. W ork am plitude reinforces the chrono-biological aspects o f accidents. W alselben (1994) in a study o f the State o f N ew Y ork, noted that 44% o f all types o f accidents attributed to sleepiness occurred betw een 1 and 7 a.m. vs. 10% in the overall sam ple. H om e (1995) states that in G reat Britain in accidents due to fatigue there is a daytim e peak around 4 p.m. and tw o night-tim e peaks around 2 a.m. and 6 a.m. M. C hiron (1986), w hen preparing an epidem iological survey on the pathologies o f t truck drivers w orking in larger than average com panies asked a doctor to com plete 250 questionnaires

6 Sleeping tim e varied w idely from 3 hours 30 m inutes per night to 9 hours 30 m inutes. M ean duration w as 6 hours 45 m inutes per night - w hich is relatively short. 8 % slept under 6 hours. A second survey (Le Provost et al.) on long-distance truck drivers show ed that those w orking in shifts slept from 4 to 7 hours and those driving alone from 5 to 7. An extract from research by G erm ain highlights the significance o f daily variations in sleep duration as well as driving duration (see p 9). T his short sleep duration factor has a high im pact on fatigue. B ut specialists consider that the m ost im portant param eter is the total duration o f w ork rather than the tim e spent driving alone. Already suggested by L isper (1986), this distinction w as confirm ed by A kerstadt (1993) w ho observed that the total tim e spent at w ork had a better correlation w ith sleepiness, assessed on a self-scoring scale than on driving duration. Raggat (1990) studied drivers o f long-distance coaches and, m ore particularly, stress factors. T he num ber o f hours spent at the w heel closely correlates w ith sleep disorders. This study also identifies interrupted rest, catching up on schedules and end o f a trip fatigue as sources o f stress. V allet (1987) exam ined the low quality o f long-distance truck drivers' sleep w ith gradual degradation and m odifications to REM sleep during the w eek, considered to be an invariable param eter. R ecovery over the w eekend is, in m ost cases, insufficient. H ow ever not all problem s o f sleepiness, the biological basis o f lack o f concentration, are related to lack o f sleep. There are natural and pathological sleepiness conditions and in these cases, alcohol, narcotics and/or m edication lowers awareness and increases the risks o f accidents. In sleep disorders and hypersom nia, it is essential to differentiate betw een excessive sleepiness during the daytim e as described by Billiard (1984) and the sudden sleep o f bus drivers studied by A rbus (1984). A survey o f 27,141 young soldiers drew attention to involuntary sleep periods : 15.1% fell asleep occasionally, 3.1% one o r tw o tim es a day and 1% m ore than twice a day. It should be rem em bered that young adults fall asleep very quickly. A small num ber o f cases o f paroxystic hypersom nia have been studied; this is a pathological condition rather than fatigue and is som ew hat difficult to identify. H ow ever the consequences constitute a road safety risk factor. Experim ents into m assive sleep deprivation dem onstrate m odifications to psychological behaviour and neurosensorial capacities. It is easy to im agine the im pact on driving. People deprived o f sleep find it very difficult to concentrate for sustained periods and becom e m ore and m ore aggressive, irritable and less sociable. M ontplaisir (1995) show ed that hypersom niacs m ake significantly m ore driving errors in a 30 m inute test on the sim ulator (running o ff the road, crossing the continuous central o r roadside lines and failing to respect road signs) than the control group. F o r M ontplaisir only hypersom niacs run o ff the road and this seem s to be related to m icro-sleep. T he sim ulated driving test seem s sufficiently sensitive to detect drivers w ho could fall asleep w hen driving

7 O ver the last 10 years o r so, particular attention has been devoted to sleep apnoea and its impact on daytim e sleepiness w hich can becom e hypersom nia. L eger (1995) gives a good sum m ary o f the general problem, the state o f our know ledge and risks o f accidents. Sleep apnoea syndrom e is characterised by the appearance o f respiratory arrests during sleep. T hese last under 10 seconds but can occur 5 or m ore tim es per hour. A ccording to the literature, 1 to 8.5% o f the population suffer from this disorder. In m en the problem increases w ith age : 8 to 15% after 40, 25% over 65 and is often associated with cardiovascular disorders. D aytim e sleepiness, and its im pact on car driving, appears in 60% o f people suffering from sleep apnoea vs. 3 to 12% in general. People suffering from sleep apnoea have five tim es m ore accidents and accidents due to sleepiness are m ore num erous, 13% vs. 3% in the control group. "N ear m isses" are 9 times m ore frequent. In addition to this bibliographic approach, L eg er's research com pared 90 w orkers suffering from sleep apnoea with 50 w orkers in a control group including m ore w om en. The in-depth questionnaire used dem onstrates results fo r sleepiness in trucking for accidents at w ork and on the road : - in trucking, sleepiness concerns : % o f sleep apnoea sufferers in the m orning vs. 4% o f the control group 62% o f sleep apnoea sufferers in the evening vs. 26.5% o f the control group, the w ork accident rate is identical in both groups but sleep apnoea sufferers have m ore "near m isses" (14.9% vs. 0% ), - sleep apnoea sufferers have m ore road accidents, but the difference is not significant (7.3% vs. 2% ). 34.5% o f sleep apnoea sufferers vs. 4% in the control group say they have alm ost had an accident and am ong those with apnoea, sleepiness is the m ost frequent reason given. Sm iley (1995) states that Canadian drivers with sleep apnoea problem s perform less well in trajectory-follow ing tests and visual exploration than healthy subjects and those w ith 0.08 g/h alcohol in their blood. Fortunately, sleep apnoea can be treated successfully. In a specific study o f fatigue-related truck accidents, M aycock (1995), discussed the possibility o f sleep apnoea and supposed, narcolepsy sym ptom s in drivers due to extrem e results scored on the Epw orth sleep scale. A ustralia has run several sleep apnoea research program m es. B earpark (1989), com pared accident rates in three different groups o f car drivers : sleep apnoea sufferers, snorers and a control group. Sleep apnoea sufferers stating they had had accidents caused by sleepiness is significantly higher (19% ) than snorers (3% ) and the control group ( 8 % ). 57% o f "sleep apnoea sufferers" reported that due to sleepiness they had run o ff the road several tim es o r frequently (w ithout an accident) vs. the "snorers" (32% ) and the control group (33% ). Sleep apnoea sufferers and snorers fell asleep m ore often at traffic lights than the control group

8 B ased on the observations m ade by Bolz (1988) and G illespie (1988) o f the alarm ing num ber o f truck drivers suffering from sleep apnoea, Bearpark recom m ended m ore detailed m edical exam inations for truck drivers, because their lifestyle (obesity and the consum ption o f alcohol and the tasks their jo b involves, particularly long distance driving, im plies greater risks o f falling asleep at the w heel. Stradling (1989) concluded that "all sleep apnoea sufferers holding driving licences for public o r goods vehicles should be invited to stop driving until they have com pleted a successful m edical treatment". Pakola and D inges (1995), during a review o f regulations concerning sleep d isorders and driving, observe that the general rule is to prevent drivers from driving fo r 3 to 12 m onths so that they can seek effective therapy even if it has not been fully elucidated w hether accident risks are higher or not. C O N C L U S IO N S Truck drivers drink m oderate am ounts o f alcohol and it seem s probable that actual p rogress in this pattern is extrem ely recent. N arcotics, m edication and stim ulants are alm ost m ore w idespread than alcohol. The im portance o f w orking conditions and sleep disorders has also been em phasised. C onfronted with these m any factors contributing to driver lack o f vigilance, it seem s sensible to suggest that an effort be m ade to globally im prove drivers irregular hours and w orkday length. O ther approaches w ould consist in providing full inform ation and even organising continuous training program m es about the facts that alcohol and m edication increase natural risks and those induced by sleep disorders. R E F E R E N C E S A kerstedt T., Folkard S. : Q uantitative m odel for vigilance, in V allet-k hardi 1995 PU L. A rbus L X em e C ongres SIR M C E-Paris. Biecheler-Fretel M -B. et al. RTS n p Billiard M., A lperovitch A. Excessive daytim e som nolence. 1984, Congres SIRM CE. Botto P. SIA congress Chiron M. et a l : E nquete epidem iologique : rapport IN R E TS n 74. G erm ain C. et a l : Le transport au quotidien. Synthese IN R E TS n 18, 1992, B ron, 65 p. H am elin P. 3rd int. C onf. on Survey m ethods in transportation. W ashington D C, H am elin P. : Le travail des conducteurs routiers. A ctes congres SIA , 23 p. H aw orth N.L. : R eport n 3 - M elbourne U niversity A ccident R esearch Centre. H aw orth N.L. et al report n 18, 80 p M elbourne U niversity A ccident R esearch Centre. H orne J., R eyner L ; Sleep related accidents, BM J. 1995, 310, H orne J., R eyner L., F alling asleep at the w eek R eport T R L n 168, C row thorne 1995, 45 p

9 K nipling R., W ang J-S. : C rashes related to D river D row siness fatigue. U S D O T nov L agier G. Psychotropes et accidents de la route, in V allet-k hardi 1995 PU L pp Lahy B. n l T ravail H um ain, 1937 Le P rovost Y., L eng F., M ignot G. Societe de M edecine du travail, R ennes 1993, 11 p. L eger D. : Syndrom e d'apnees du som m eil et risques accidentels, in V allet-k hardi 1995 PU L. L isper FLO. et al E rgonom ics 29, M ackie R M iller J-C D O T -H S-5-O l 142. N TIS PB M aycock G. D river sleepiness as a factor in car and H G V accidents. R eport T R L n 169. M C D onald N F atigue, safety and the truck driver. T aylor et F rancis - L ondres. 248 p. M onplaisir J. : P erform ances des hypersom niaques, in V allet-k hardi 1995 PU L pp M ontastruc J-L Therapie. 43, O uverkerk V. l i e Sym posium international C.E.M.T., Bruxelles, P akola S.J., D inges D. F Pack A. I., 1995 Sleep 18(9) pp R am et M., V allet G. : Securite et M edecine du Travail, 1987 n 78 R oussel B. et a l : S om nolence et pharm acologie in V allet-k hardi pp PUL. Sm iley A. et a l : D riving im pairm ent o f sleep apnea patients, in V allet-khardi 1995 PUL. S um m ala H., M ikkola T. : Fatal accidents am ong car and trucks drivers. H um an factors V allet M., Blanchet V. : Securite et M edecine du Travail, 1987 n 78 pp V allet M., K hardi S : V igilance et T ransports : Presses U niversitaires de L yon. 424 p. W alsleben L : T he im pact o f fatigue on driving U S, 1TSM R and N.Y. State, D ec 1994, 24 p