Freight transport and non-driving work duties as predictors of falling asleep at the wheel in urban areas of Crete

Abstract

Background: This study investigated the impact of subjective reports of drowsy driving and non-driving duties on the falling asleep responses and road crash involvement of professional drivers in Crete. An attempt was also made to elucidate other driving parameters, such as freight transportation, which could be potential predictors of risky driving, after controlling for lifestyle patterns. Method: A sample of 317 professional drivers was studied through personal interviews. The interview questionnaire included items about sleep and fatigue as contributing factors to falling asleep probability and crash risk. In addition, the drivers reported the type of freight they carried in their last trip, as well as practices such as smoking and alcohol consumption. Results: The first logistic regression analysis showed that the most significant predictors of falling asleep at the wheel were transportation of fruits/vegetables and livestock, non-driving hours of work, insufficient hours of sleep, and smoking. The second logistic regression analysis revealed all the previous items as powerful factors of crash probability, including the transportation of express freight and freezer. Impact: The findings of the current study are discussed as they pertain to directions for future studies and for the development of fatigue countermeasures.

Introduction

Driving is regarded as a skillful task that requires sustained vigilance and quick reaction times. Sleepiness, on the other hand, is a basic physiological state, which, when appears while driving, impairs a driver's performance. Sleepiness and driving cannot coexist if road crashes are to be avoided. The risk for being involved in road crashes caused by sleepiness or falling asleep at the wheel, is increased for professional drivers whose job makes great demands on their time. Driving a heavy truck or a bus usually includes many other tasks in addition to driving the vehicle (e.g., multiple deliveries in a single trip, loading and unloading). Professional drivers may also have to be at the wheel for many hours a day and many days a week, a practice that usually results in irregular sleep habits. Under these work conditions, professional drivers are thought to be at a higher risk for being involved in a sleepiness-related road crash.

The research presented here was carried out on the island of Crete, the biggest island of Greece, located in the most southern edge of the country. The residents of the island deal mainly with agriculture, cattle breeding, tourism, and trade. Large quantities of agricultural products and livestock are transported daily from several rural regions of the island to the big urban centers as well as to other cities of Greece. Moreover, a great number of tourists visit the island during the summer season. The great growth in the sectors of trade and tourism in the last decades has resulted in greater need for professional drivers and vehicles, and a growing demand on their work. Consequently, truck crashes have increased.

Information regarding the island of Crete, provided by the Greek Traffic Police, indicate that 1,014 road crashes occurred within the years 1998–2001, out of which 188 were fatal and 393 had serious injuries. Moreover, analyzing the data regarding the whole country for the years 1995–2001, almost 150,000 road crashes (fatal and non-fatal) occurred throughout Greece (nearly 25% involved heavy trucks and 1% buses). Based on these heavy vehicle estimations and after taking into consideration that 10% of the total truck crashes are fatal, scientific research on drowsy driving among professional drivers is necessary (Greek Traffic Police, 2001).

The contribution of sleepiness as a cause for road crashes cannot be estimated because accidents rarely leave any sign to indicate that the driver had been sleepy or fell asleep at the wheel. Besides that, Greece has no official accident-reporting document with which the driver, soon after the crash, could report their point of view about the cause of their crash. Such a procedure seems significant for finding the real causes of a road crash and also for reporting sleepiness-related crashes (assuming that “sleepiness” is included among the driver's choices; Papadakaki & Chliaoutakis, 2002).

The absence of an official document means that sleepiness is rarely reported as a cause of road crashes, since it is rarely suspected by the police as a possible road crash cause and since potential liability may motivate the drivers not to reveal the real causes of their crash. Sleepiness is thus under-recognized, as has been identified by other researchers (Brown, 1994, Fell, 1994). It could be suggested that distraction, which is claimed responsible for 15% of all the heavy vehicle crashes in Greece for the years 1995–2001, is used as a substitute or what appears as a result of sleepiness (see previous research: Dinges, 1995, Brown, 1994).

Based on the above, it is obvious that there is no official data on the prevalence of drowsy driving in Greece and consequently no “material” for scientific analysis. Therefore, this study is a first attempt to address the drowsy driving problem among professional drivers in Greece.

The limited research in Greece on the problem of drowsy driving may be contrasted with the level of knowledge in other countries, where the problem of sleepiness or falling asleep at the wheel has long been recognized and meticulously studied. A number of studies, deriving from different countries, illustrate the drowsy driving problem and its dimensions. A significant relationship between the probability of feeling close to falling asleep at the wheel and variables such as Epworth score, age, annual mileage, proportion of time spent driving on motorways as well as roads in built-up areas and occupational group, was found in a mail survey in Great Britain (Maycock, 1997). More precisely, a higher Epworth score increased the probability that a driver would feel close to falling asleep at the wheel and so did the proportion of time spent driving on motorways and the annual mileage. On the other hand, age had a negative effect and the proportion of time spent driving in built up areas decreased the probability of feeling close to falling asleep. Research has also shown that there are certain driver characteristics such as demographic and other variables related to sleep, work, and driving patterns that appear to be associated with increased frequency of driving drowsy (McCartt, Ribner, Pack & Hammer, 1996). Another view suggests that excessive hours of work increase driver fatigue (Arnold et al., 1997), while others have identified daytime sleepiness to be a most highly predictive variable for falling asleep at the wheel. Other predictive variables were an arduous work schedule and older, long-time drivers (McCartt, Rohrbaugh, Hammer & Fuller, 2000). The effects of time of day are suggested by others to have an effect on increased vulnerability in sleep-related driving accidents, particularly in the early morning hours and mid-afternoon hours (Horne & Reyner, 1995, Kecklund & Akerstedt, 1994). It was also found that lack of awareness of important precursors of falling asleep as well as a reluctance to discontinue driving despite feeling tired, are likely contributors to sleepiness-related road crashes (Sagberg, 2001).

The purpose of the current study was to investigate more closely how the extent of road crashes among professional drivers as well as the prevalence of falling asleep while driving can be predicted on the basis of background and other work-related information about the drivers. The main hypotheses examined were that excessive hours spent on non-driving work and less hours of sleep obtained are positively related to falling asleep at the wheel and involvement in a road crash. This study will provide information: (a) to gain a better understanding of the safety issues in the transportation industry; and (b) to propose developing possible countermeasures related to road safety in professional drivers in Greece.