What Is Fatigue and How Does It Affect the Safety Performance of Human Transport Operators?
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TØI report 1351/2014 Ross Owen Phillips What is fatigue and how does it affect the safety performance of human transport operators? Fatigue in Transport Report I TØI Report 1351/2014 What is fatigue and how does it affect the safety performance of human transport operators? Fatigue in Transport Report I Ross Owen Phillips This report is covered by the terms and conditions specified by the Norwegian Copyright Act. Contents of the report may be used for referencing or as a source of information. Quotations or references must be attributed to the Institute of Transport Economics (TØI) as the source with specific mention made to the author and report number. For other use, advance permission must be provided by TØI. ISSN 0808-1190 ISBN 978-82-480-1562-8 Electronic version Oslo, November 2014 Title: What is fatigue and how does it affect the safety Tittel: Hva er trøtthet og hvordan påvirker det sikkerhetskritisk performance of human transport operators? atferd under framføring av transportmidler? Author(s): Ross Owen Phillips Forfattere: Ross Owen Phillips Date: 09.2014 Dato: 09.2014 TØI report: 1351/2014 TØI rapport: 1351/2014 Pages 103 Sider 103 ISBN Electronic: 978-82-480-1562-8 ISBN Elektronisk: 978-82-480-1562-8 ISSN 0808-1190 ISSN 0808-1190 Financed by: The Research Council of Norway Finansieringskilde: Norges forskningsråd Project: 3719 - Kunnskap om trøtthet og nedsatt Prosjekt: 3719 - Kunnskap om trøtthet og nedsatt vaktsomhet blant transportoperatører vaktsomhet blant transportoperatører Project manager: Ross Owen Phillips Prosjektleder: Ross Owen Phillips Quality manager: Torkel Bjørnskau Kvalitetsansvarlig: Torkel Bjørnskau Key words: Driver Emneord: Sjø Fatigue Trafikksikkerhet Occupation Trøtthet Road safety Yrkessjåfør Sea Summary: Sammendrag: The ability to manage human fatigue in transport operations Prioriteringen av trøtthet som en risikofaktor i transport er avhengig would be improved by a shared understanding of what fatigue av en delt forståelse om trøtthet, om hvordan det bør måles, og om is, how it should be measured, and how it affects safety hvordan det påvirker sikkerhet. En felles forståelse kunne oppnås performance. This may be achieved by a broader ved å anerkjenne trøtthet som et bredt begrep med ulike operationalization of fatigue, which would allow commonly dimensjoner som bør måles, og som sammen beskriver studied aspects of fatigue to be considered alongside each erfaringsmessige aspekter, fysiologiske aspekter, og prestasjon. En other, and make explicit those aspects of fatigue that individual slik tilnærming ville klargjøre aspekter av trøtthet som ulike studier studies do and do not account for. According to such an ikke tar hensyn til. Det er også behov for økt overveielse av trøtthets operationalization, fatigue should be measured in terms of langsiktige effekter hos menneskelige operatører. For å forstå experience, physiological state and performance. In studying hvordan trøtthet påvirker prestasjon, må vi ta hensyn til the effects of fatigue on operators, there would be a need to for interaksjonene mellom søvn, døgnrytme, «time-on-task» i greater consideration of its longer-term effects, and its sammenheng med faktorer som beskriver ulike aspekter av livet, motivational aspects. To understand its performance effects både innenfor og utenfor arbeid. would require that we attend to the systematic interaction of sleep history, time of day, time at work, and time on task, in the context of factors describing various aspects of work and non-work life. Language of report: English This report is available only in electronic version. Rapporten utgis kun i elektronisk utgave. Institute of Transport Economics Transportøkonomisk Institutt Gaustadalleen 21, 0349 Oslo, Norway Gaustadalleen 21, 0349 Oslo Telefon 22 57 38 00 - www.toi.no Telefon 22 57 38 00 - www.toi.no Copyright © Transportøkonomisk Institutt Denne publikasjonen er vernet i henhold til Åndsverkloven av 1961 Ved gjengivelse av materiale fra publikasjonen, må fullstendig kilde oppgis What is fatigue and how does it affect the safety performance of human transport operators? Preface This report is part of the project «Fatigue in Transport» (FiT), which has been carried out within the TRANSIKK programme («Transport sikkerhet») of the Research Council of Norway. The main objective of the project was to increase what we know about fatigue in human transport operators in the road, maritime and rail sectors in Norway. In an early phase of the project, it became clear that we needed to operationalise fatigue explicitly, not least in order to be able to compare findings from Norway with those from other countries. On investigation, however, we found few accounts of how fatigue should be operationalised for the study of human transport operators. This report attempts to fill this gap by explaining how we defined and thought about fatigue in relation to human operator safety. It also explains how we surveyed and assessed operationalised measures of fatigue for the purposes of assessing its health and safety implications. We hope that this report may be of use to those embarking on studies of fatigue in the future, who may also face the daunting task of reviewing the considerable literature on fatigue in order to decide how to measure and think about it. The project manager and report author, Ross Owen Phillips, wishes to thank Torkel Bjørnskau, Fridulv Sagberg, and Tor-Olav Nævestad for comments and discussions in the development of the report. Sagberg also translated the summary into Norwegian. Torkel Bjørnskau has also quality assured the report. Trude Rømming has been involved in editing the report and preparing it for publication. Oslo, November 2014 Institute of Transport Economics (TØI) Gunnar Lindberg Torkel Bjørnskau Managing Director Chief Research Political Scientist What is fatigue and how does it affect the safety performance of the human transport operators? Contents 1 Background ................................................................................................. 1 2 Introduction ................................................................................................ 3 3 Aim .............................................................................................................. 5 4 How should we define fatigue? ................................................................... 6 4.1 Everyday usage...................................................................................................... 6 4.2 Fatigue as an experience ...................................................................................... 6 4.3 Fatigue as a physiological condition .................................................................. 9 4.4 Fatigue as performance decrement .................................................................... 9 4.5 Fatigue as a multidimensional construct ......................................................... 10 4.6 Definition for the study of fatigue in human transport operators .............. 11 4.7 Dualistic accounts of fatigue ............................................................................. 13 4.8 Summary .............................................................................................................. 15 5 How should we think about fatigue? ........................................................ 16 5.1 Models of sleepiness .......................................................................................... 16 5.2 Does fatigue add anything useful to sleepiness? ............................................ 19 5.3 The physiology of fatigue .................................................................................. 21 5.4 Conceptual models of fatigue ........................................................................... 22 5.4.1 Distinguishing fatigue from stress ..................................................... 23 5.4.2 Fatigue as an indicator allowing for adaptation to work by changing resources and strategies ...................................................... 24 5.4.3 Compensatory control model (CCM)................................................ 26 5.4.4 Dynamic Model of Stress and Attention .......................................... 29 5.5 Summary .............................................................................................................. 31 6 How should we measure fatigue? ............................................................. 35 6.1 Subjective measures ........................................................................................... 36 6.1.1 Popular scales for measuring fatigue ................................................. 37 6.1.2 Measuring fatigue in working populations........................................ 44 6.2 Objective measurement ..................................................................................... 46 6.2.1 Measures of physiology ....................................................................... 46 6.2.2 Measures of sleep propensity and sleep behaviour ......................... 47 6.2.3 Measures of performance .................................................................... 48 6.3 Measuring the effects of compensatory activity............................................. 49 6.4 Summary .............................................................................................................. 50 7 Effects of fatigue on performance and accidents ..................................... 52 7.1 Effects of sleep deprivation .............................................................................