Train driving efficiency and safety: examining the cost of fatigue
JILLIAN DORRIAN, FRANK HUSSEY and DREW DAWSON
The Centre for Sleep Research and the School of Psychology, The University of South Australia, Adelaide, SA 5000, Australia. Accepted in revised form 3 October 2006;received 8 February 2006
ABSTRACT
This study investigated the effects of fatigue on train driving using data loggers on 50 locomotives operated by pairs of male train drivers (24–56 years) on an Adelaide– Melbourne corridor. Drivers work history was used to calculate a fatigue score using Fatigue Audit Interdyne Software. Trains were assigned to one of three groups, based on drivers maximum fatigue score: low (n ¼ 15), moderate (n ¼ 22) or high (n ¼ 13) fatigue. Changes in driving parameters at different fatigue levels were investigated. A significant (P < 0.05) increase in fuel use was observed. Drivers in the moderate fatigue group used 4% more, and drivers in the high group used 9% more fuel than drivers in the low group. As these trains run daily, taking horsepower into account, this represents an approximate extra weekly cost of AUD$3512 using high compared with low fatigue drivers. High fatigue-group drivers used less throttle and dynamic brake and engaged in more heavy brake and maximum speed violations. Comparison of three, 100 km track sub-sections with undulating, flat, and hilly grade indicated that fuel use increases occurred primarily during the undulating sub-section, and heavy brake and maximum speed violations occurred primarily in the flat sub-section. Fatigued driving becomes less well-planned, resulting in reduced efficiency (e.g. increased fuel consumption) and safety (e.g. braking and speeding violations). Fatigue may manifest differentially depending on track grade. In certain areas, fatigue will cause increased fuel use and economic cost, and in others, reduced safety through driving violations. These factors should be carefully examined in future railway operator research. keywords cost, efficiency, fatigue, safety, train driving
INTRODUCTION
Sleep loss and fatigue are serious issues for train drivers, whose work hours are often long and uncertain and involve night and early morning shifts (Foret and Latin, 1972; Ha¨ rma¨ et al.,2002; Pilcher and Coplen, 2000; Pollard, 1991, 1996; Roach et al., 2003). Studies collecting subjective reports (A˚ kerstedt et al., 1983) and polysomnographic sleep measures (Cabon et al., 1993; Torsvall and A ˚ kerstedt, 1987) have recorded periods of drowsiness and even microsleeps while driving. Rail accident reports in numerous countries, including Australia, China, Japan and the US have cited work-related fatigue (Pearce, 1999; Zhou, 1991) and the ability of the driver to maintain wakefulness (Kogi and Ohta, 1975; Lauber and Kayten, 1988) as contributing agents. While sleepiness has been simply defined as a drive towards sleep (Dement and Carskadon, 1982), defining the concept of fatigue has proved to be more complex. Recent attempts have focused on dualistic approaches (i.e. acute versus chronic, physiological versus psychological) (reviewed in Shen et al., 2006). While there may be merit for specifically defined differences between the concepts of sleepiness and fatigue, it is generally acknowledged that these concepts are highly interrelated (Shen et al., 2006). Based on previous work (Brown, 1994; Bartley and Chute, 1947; Cameron, 1974; Yoshitake, 1971), this paper will use a working definition of fatigue as a subjective phenomenon that is connected with the desire to rest and is associated with unpleasant psychological and physiological sensations. Further, like sleepiness, fatigue is conceptualized as the result of inadequate restorative sleep and rest and excessive time awake, and is modulated by time of day. Correspondence: Jillian Dorrian, Lecturer in Psychology, The Centre for Sleep Research, The University of South Australia, 7th Floor Playford Building (P7-35), City East Campus, Frome Rd, Adelaide, SA 5000, Australia. Tel.: +61 8 8302 6624; fax: +61 8 8302 6623; e-mail: jill.dorrian@unisa.edu.au J. Sleep Res. (2007) 16, 1–11, 2007 European Sleep Research Society 1