Women’s Issues in Transportation: Summary of the 4th International Conference, Volume 2: Technical Papers (2011)

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26 Investigation of Differences in Crash Characteristics between Males and Females Involved in Fatigue-Related Crashes or Close-Call events Kerry Armstrong, Patricia Obst, Kerrie Livingstone, and Narelle Haworth, Centre for Accident Research and Road Safety, Queensland, Australia There is consensus among community and road safety agencies that driver fatigue is a major road safety issue, and it is well known that excessive fatigue is linked with an increased risk of a motor vehicle crash. Previous research has implicated a wide variety of factors involved in fatigue-related crashes, and the effects of these various factors in regard to crash risk can be interpreted as causal (e.g., alcohol or drugs may induce fatigue states) or additive (e.g., where a lack of sleep is combined with alcohol). This investigation examined self-report data to determine whether there are any differences in the prevalence, crash characteristics, and travel patterns of males and females involved in fatigue- related crashes or close-call events. A representative sample of residents (N = 1,600) living in the Australian Capital Territory and New South wales, Australia, were surveyed regarding their experience of fatigue and their involvement in fatigue-related crashes and close- call incidents. Results revealed that more than 35% of the participants reported having had a close call or crash caused by driving when tired in the 5 years prior to the study. In addition, the results obtained revealed a number of interesting characteristics that provide pre- liminary evidence that gender differences do exist in the prevalence, crash characteristics, and travel patterns of males and females involved in fatigue-related crashes or close-call events. It is argued that the results obtained can provide particularly useful information for the refinement and further development of appropriate countermeasures that better target this complex issue. It has been well established nationally and interna-tionally that sleep- and fatigue-related driving is an important contributory factor in fatal and serious injury crashes. Fatigue and sleepiness are seen to be the largest identifiable and preventable causes of transport crashes (15% to 20% of all crashes), surpassing alcohol or drug-related crashes (1, 2). It is estimated that fatigue may be a leading cause of accidents in anywhere up to 25% of cases reported in the aviation industry (3, 4). Additionally, fatigue is purported to contribute to approximately 35% and 16% of personal injury and vessel accidents, respectively, in the maritime industry (5). In the rail industry, fatigue was implicated as a contributing factor in 112 train accidents and near misses that occurred in Australia over a 3-year period (6). Studies in the motor vehicle industry suggest that 20% of all motorists on the road have fallen asleep at least once while driving and that one-third of fatal crashes involving truck drivers is due to fatigue (7). Excessive fatigue has been linked with an increased risk of a motor vehicle crash, either because the motorist falls asleep while driv- ing or because he or she experiences reduced attention to road events and driving tasks because of fatigue or sleepiness (1, 8). These studies highlight the pervasive and problematic nature of fatigue across all areas of the transport industry. The causes of sleepiness while driving and driver fatigue are numerous and interact in complex ways. Fac- tors that may contribute to driver sleepiness and associ- ated crashes include sleep debt, shift work, prolonged work hours, time of day, time spent awake, time on

27DIFFERENCES IN CRASH CHARACTERISTICS BETwEEN MALES AND FEMALES task, type of road, risk-taking behavior, age and gender, sleep disorders, alcohol and other drugs, and familiarity with the road environment (1, 9, 10). Most significant, though, is that sleep-related crashes are likely to be more severe than other crashes (because of high speed) and to result in higher fatalities (1, 11). As such, there is little doubt that sleepiness or fatigue while driving represents a significant social and economic cost to the community in relation to road crashes, especially fatal road crashes. Sleep loss is one area of fatigue research that has been vigorously studied across many disciplines, which is testament to the strong links that are purported to exist between lack of sleep and fatigue. Over the years, researchers have devoted much attention to investigating fatigue by focusing on the deleterious effects that sleep deprivation can have on cognitive performance and motor skills. Research suggests that a lack of sleep (e.g., 4.5 h compared with 7.5 h) can lead to significant impairment in driving performance (12), with individuals who obtained less than 6 h of sleep being twice as likely to be involved in a dangerous event while driving (13, 14). Other more recent studies also revealed that moderate amounts of sleep deprivation can result in impairments to cognitive and motor skill performance that are equal to or greater than those found at the legal blood alcohol concentration (BAC) driving limit in many jurisdictions (15–19). As little as 17 h of extended wakefulness can generate deterioration in driving performance equivalent to a BAC of 0.05%, the legal limit in many jurisdictions (20, 21). Numerous investigations have also revealed that when fatigued or sleepy drivers consume even small amounts of alcohol, they experience greater impairment in their driving performance (10, 22). For example, in one investigation that combined partial sleep deprivation and BAC, Banks et al. found that drivers experienced impaired driving (when driving in a simulator) and more microsleep events (short episodes of unintentional sleep onset during driving) and reported poor ability to predict crash risk (22). when partially sleep deprived, women appeared to be either more perceptive of increased crash risk or more willing to admit to their driving limitations than the men studied. Neither men nor women, however, were capable of accurately predicting crash risk when they were both sleep deprived and alcohol impaired. Traditionally, vehicle crashes in which illegal BACs were detected had alcohol intoxication identified as the major cause (9); however, such research indicates that fatigue and alcohol interact, even at legal levels, resulting in greater impairment to driving performance than caused by fatigue or alcohol alone (10, 22). Other investigations have focused on time of day and monotonous driving conditions. For example, Horne and Reyner found falling asleep at the wheel to be a common cause of road crashes on dull and monotonous roads, with 16% of all police-attended vehicle crashes on major roads and 20% of police-attended vehicle crashes on motorways being attributed to fatigue (2). Further, major peaks in road crashes were found at around 2 a.m., 6 a.m., and 4 p.m. The police reports noted that half the drivers in these crashes were men under 30 years of age. In a later investigation, Reyner and Horne found that as subjective sleepiness in drivers worsened, so did the number of incidents (23, 24). In their investigation, driv- ers had modest sleep restrictions imposed on the night prior to their drive, which intensified the natural midaft- ernoon circadian peak in sleepiness. Further, when driv- ers were fighting sleepiness, both minor and, especially, major incidents worsened markedly. A study by Smith et al. found a late-night and early- morning increase in crash risk that was most pronounced for serious and fatal crashes, young drivers (three times the odds) and male drivers (more than twice the odds) (25). In contrast, older age groups had a lower risk of crash at night than during the morning. The increased risk of crash for fatal crashes among 17- to 24-year-old males was more than nine times the odds of that for young females. Both absolute and relative risk estimates supported an overrepresentation of males (particularly young males) in early morning crashes, a risk that is con- sistent with other studies (26). Similar results have been observed in an investigation of vehicle crashes attributed to fatigue or falling asleep in low-speed urban environments of 60 km/h or less in Queensland, Australia (27). Even though much research points to young male drivers (ages 16 to 24 years) being most at risk for fatigue or sleep-related vehicle crashes, research also shows that older drivers are more likely to be involved in afternoon fatigue-related crashes. As people grow older, the after-lunch drop in circadian rhythm becomes more apparent, affecting performance and, therefore, increasing the risk of fatigue-related crashes (2, 9, 11, 28). An alarming trend found in a recent Australian survey is that almost half of those who reported having ever fallen asleep had done so more than once, and 13% had fallen asleep while driving on three or more occasions (29). In 12% of recent incidents of having fallen asleep while driving, a road crash resulted. Again males were significantly more likely than females to report having ever fallen asleep while driving. Overall, it was found that drivers are generally more likely to fall asleep on trips of more than 2 h duration when driving on country roads and highways as well as between midnight and 6 a.m. (29). Sleep does not happen spontaneously without warn- ing. Drivers falling asleep are not likely to recall having done so, but will be aware of increasing sleepiness and will most likely reach a stage of fighting off sleep before

28 wOMEN’S ISSUES IN TRANSPORTATION, VOLUME 2 crash risk, can lead drivers to underestimate the shift from sleepiness to sleep (9, 11, 31). Research suggests that many drivers are aware that they are sleepy when driving but do not act accordingly (11, 23); however, drivers experiencing fatigue may only be vaguely aware of the withdrawal of attention and decline in their own cognitive processing (20). Finally, even though fatigue and sleepiness at the wheel are well-known risk factors for traffic crashes, this knowledge does not discourage many drivers from combining sleep deprivation and driving (23, 35, 36). Although there is little doubt that fatigue represents a significant social and economic cost to the community in relation to road crashes, especially fatal road crashes, there has been a lack of research examining any differences in the type of fatigue-related crashes experienced by men and women. In one of the few studies to directly examine the effects of gender, fatigue, and driving performance and perception, Baulk et al. found that when exposed to extended wakefulness, females responded more slowly in visual reaction tasks and rated their driving worse than males (37). This could be one (of many) explanations for why men are over-represented in fatigue-related crash statistics as compared with women. The reason males consistently emerge with a higher fatigue-related crash rate may be the product of several commonly assumed factors (e.g., men driving more often and driving longer distances), but it also may be because they consider the impact of sleep deprivation on their driving ability to be less detrimental than women do. The purpose of the current investigation was to add to the literature regarding gender differences in the expe- rience of driving when tired. This research explores such gender differences in detail by examining a sample of responses from both males and females who had expe- rienced a close call or crash as a result of driving when tired. Such research is important to understanding how fatigue-related incidents occur within the typical driving patterns of men and women, and it provides a starting point for exploring whether males and females experi- ence and understand the risk of driving when tired in the same way. This has implications for educational cam- paigns and interventions aimed at reducing the incidence of fatigue-related road crashes. Method Participants The study participants were 1,609 drivers residing in New South wales, Australia, and the Australian Capi- tal Territory. Eligible respondents were ages 17 years or over, held a current drivers license, and drove more than 1 h per week. There were 805 males and 804 females. a crash (23). Most drivers involved in sleep-related vehicle crashes usually deny having fallen asleep, with evidence pointing to the crash being sleep-related com- ing from other sources. Possible reasons for the denial could include fear of prosecution and loss of insurance indemnity. It is possible, however, that the person genu- inely had no memory of having fallen asleep, with studies showing that drivers who fall asleep typically deny hav- ing been asleep if awoken within a minute or two (30). It is very likely, however, that drivers falling asleep at the wheel were aware of the precursory feeling of sleepiness, even though they may also not remember this after the crash (30). In one Norwegian study, for example, Nordbakke and Sagberg reported that most drivers experience a variety of symptoms of sleepiness before they fall asleep during driving (31). These symptoms include subjec- tive feelings of drowsiness, difficulty keeping eyes open, yawning, recurrent eye blinking, difficulty concentrating, changing position, slower reaction times, increased speed variation, a dreamlike state of consciousness, impaired performance, misjudgements of the road or traffic, deci- sion-making impairment, and freezing (20, 29). There were only minor differences between men and women in the symptoms they recognized as sleepiness, with men encountering more difficulties keeping their eyes open than women. Also, women reported more freezing and variation in speed than men as symptoms of their sleepi- ness (31). Further, microsleep events pose concerns for sleepy drivers, with typical signs being prolonged eyelid closures, roving eye movements, reduced muscle tone (e.g., head rolling), and relaxation of foot pressure on the accelerator, together with major driving incidents (such as running into a vehicle in front, or weaving or drifting off the carriageway, or both) (32, 33). There is some concern that symptoms experienced by sleepy or fatigued drivers are not taken seriously enough. This may be, in part, the result of a state of altered percep- tion in which the driver may underestimate the relation- ship between the various physiological and behavioral signals on the one hand and the risk of falling asleep on the other hand (33). Also, it is possible that sleepiness affects mood, making drivers more optimistic, less cau- tious, and even more reckless with their driving (10, 33). Additionally, people with a high risk propensity may per- ceive risk differently and therefore engage in more risky driving behavior that leads to a crash resulting in injury or death (34). Reyner and Horne argue that when a situ- ation is made intrinsically safer, people may behave in a riskier manner because the overall risk they are willing to accept remains the same (24). Drivers continue to drive when sleepy or fatigued for various reasons, including work demands, pressure to reach a destination, and short journey length. This, together with a poor understanding of fatigue-related

29DIFFERENCES IN CRASH CHARACTERISTICS BETWEEN MALES AND FEMALES Ages ranged from 17 to 90 years. For males, the mean age was 38.35 years, the standard deviation (SD) was 18.63 years, and the median was 30 years; for females the mean age was 36.97 years, the SD was 16.58 years, and the median was 29 years. Procedure A telephone survey methodology was used to randomly sample drivers residing in the catchment area. The survey used a predominately forced-choice format and contained a number of questions relating to general demographics, symptoms of tiredness experienced while driving, and commonly employed countermeasures. Also included were items designed to measure the prevalence and pro- portion of incidents of fatigue-related driving, the con- text in which the incident occurred, the circumstances involved in the incident, and contributing factors. RESULTS A similar proportion of males (68.9%) and females (64.9%) reported having felt sleepy while driving in the past 5 years. However, a significantly greater proportion of males [20.8%, n  158, adjusted standardized resid- ual (ASR)  4.2] than females (12.7%, n  96, ASR  4.2) reported having had a close-call crash when driv- ing tired (c2  17.79, p < .001). The majority of both females and males who had experienced a close-call crash had experienced fewer than two such incidents; around 20% of both genders had experienced three or more close calls. Females were slightly more likely to have experienced only one close call, whereas males were slightly more likely to have experienced five or more close calls (Table 1). A small but significantly greater proportion of males (3.4%, ASR  2.5) than females (1.5%, ASR  2.5) reported having had a crash caused by driving when tired (c2  6.15, p  .013) in the past 5 years. No significant gender differences emerged in the outcome of crashes caused by driving when tired (Table 2). The age range of both males (mean  37.66 years, SD  16.82 years) and females (mean  35.91 years, SD  14.85 years) reporting either a close call or crash was 17 to 83 years. No significant gender differences emerged (Table 3). A small difference in the purpose of the journey was observed (c2  20.719, p = .036), with females more likely to report that they were dropping off or picking up children from child care (Table 4). Further, females were more likely than males to report that the close call or crash was within 5 km of their home (c2 (5 degrees of freedom [df])  11, p  .049) (Table 5) and that they had been driving for a shorter time (less than 30 minutes) when the incident occurred (c2 (5 df)  11, p  .049) (Table 6). Significant differences were not observed when the intended distance of the journey was examined, with 42% of participants reporting that the close call or crash occurred when undertaking a short journey of under 50 km and 49% reporting the incident occurred when undertaking a journey of greater than 100 km. TABLE 1 Number of Close-Call Events Reported by Males and Females Close Call Males Females Events Percentage n ASR Percentage n ASR 1 51.3 81 1.9 63.5 61 1.9 2 24.1 38 1.2 17.7 17 1.2 3 12.7 20 1.3 7.3 7 1.3 4 2.5 4 0.7 4.2 4 0.7 5 2.5 4 0.7 4.2 4 0.7 >5 6.9 11 1.7 3.0 3 1.7 TABLE 2 Outcomes of Crashes Caused by Driving When Tired for Males and Females Males Who Reported Females Who Reported Having Had a Crash Having Had a Crash Outcome of Crash Number Percent Number Percent Collided with center lane divider 2 7.7 2 18.2 Head-on crash with stationary object 10 38.5 3 27.3 Swipe crash with stationary object 3 11.5 2 18.2 Swipe crash with other road user 3 11.5 2 18.2 Rear-end crash 4 15.4 0 0 Other 4 15.4 2 18.2

30 WOMEN’S ISSUES IN TRANSPORTATION, VOLUME 2 When alcohol consumption was examined, it was found that only 9.3% of males and 6.4% females reported consuming any alcohol in the 12 h prior to their involvement in a close call or crash event. Females (16.7%, n  13, ASR  2.4) were more likely than males (6.2%, n  8) to have taken a prescription medication in the 12 h prior to their crash or close call (c2 (2 df)  7.97, p  .019). Of those, 46% of females (n  6, ASR  2.3) reported taking the medication within 1 h before the crash (c2 (1 df)  5.12, p  .023). Males and females reported experiencing similar symp- toms prior to the close call or crash, the most common being yawning (93%), difficulty concentrating (74%), changing position frequently (74%), eye blinks (70%), dif- ficulty keeping the eyes open (66%), and slower reaction times (57%). A slightly greater proportion of males (86%, ASR  1.6) than females (79%, ASR  1.6) reported continuing driving after experiencing these symptoms of tiredness. Finally, males and females reported employ- ing similar countermeasures in order to stay alert. These included stopping the vehicle (60%), getting out of the car and stretching (35%), having something to eat or drink (34%), taking a nap (12%), and changing drivers (7%). Of those who choose to continue driving, both males and females reported that they employed a number of coun- termeasures to increase their alertness, including lowering the vehicle window (40%), turning on the radio (15%), increasing the volume of the radio (34%), or changing the temperature in the car (15%). DISCUSSION OF RESULTS This investigation involved a large-scale telephone inter- view of a random sample of drivers from New South Wales and the Australian Capital Territory to determine whether gender differences exist in self-reported crashes or close-call events caused by driving when tired. The results obtained revealed a number of characteristics that provide preliminary evidence that gender differences do exist in the prevalence, crash characteristics, and travel patterns of males and females involved in fatigue-related crashes or close-call events. Out of a total of 1,609 interviews, more than 35% of the respondents reported having had a close call or crash due to driving when tired. This percentage is higher than other self-report investigations (14, 23, 29); however, it serves to reiterate that sleepy or fatigued driving is a major road safety issue that still requires a great deal of empirical investigation. Consistent with previous investigations (29, 38), males (24%) emerged as more likely to report being involved in a crash or close-call event caused by driving when tired than females (14%). In the current investigation, the pop- ulation was weighted evenly by sex, so it is clear that any gender differences emerging are not the result of sample bias. Conversely, however, significant differences in age groups were not observed between men’s and women’s TABLE 3 Age of Males and Females Reporting a Close Call or Crash Caused by Driving When Tired Males Females Age (years) Number Percent Number Percent 17–25 48 28.9 21 21.9 26–40 54 32.5 41 40.7 41–65 55 33.1 30 32.4 >65 9 5.4 4 5.0 TABLE 4 Purpose of Journey for Males and Females Reporting a Close Call or Crash Caused by Driving When Tired Males Females Purpose of Journey Number Percent Number Percent Commuting to work 40 31.0 18 23.1a Work-related trip 15 11.6 6 7.7 Social activities or leisure 33 24.7 21 29.5 Holiday travel 26 20.2 15 19.2 Shopping 1 0.8 3 3.8 Childcare 0 0.0 6 7.7b Personal care or education 8 6.2 7 8.9 Other 5 4.7 0 0.0 a ASR = –1.2. b ASR = 3.2. TABLE 5 Distance from Destination for Males and Females Reporting a Close Call or Crash Caused by Driving When Tired Distance from Males Females Destination (km) Number Percent ASR Number Percent <5a 20 15.5 –2.4 23 29.0 5–10 22 17.1 0.1 13 16.7 11–20 18 14.0 0.5 9 11.5 21–50 16 12.4 0.2 9 11.5 51–80 6 4.7 –0.5 5 6.4 81–100 11 8.5 1.3 3 3.8 101–200 17 13.2 0.9 7 9.0 201–300 10 7.8 0.7 4 5.1 >300 9 7.0 0.2 5 6.4 a ASR for females  2.4. TABLE 6 Approximate Driving Time for Males and Females Reporting a Close Call or Crash Caused by Driving When Tired Driving Males Females Time (h) Number Percent ASR Number Percent £0.5a 33 25.6 –2.4 33 42.3 >0.5£1 22 17.1 0.4 15 19.2 >1£2 27 20.9 1.5 10 12.8 >2£3 16 12.4 0.1 10 12.8 >3 31 24.0 2.0 10 12.8 a ASR for females  2.4.

31DIFFERENCES IN CRASH CHARACTERISTICS BETwEEN MALES AND FEMALES self-reporting of such incidents. Specifically, the current investigation found that males’ reporting of crashes or close calls caused by driving when tired was spread evenly for those younger than 65 years of age, whereas females in the 26- to 40-year-old age group reported more close call events or crashes than younger cohorts. when the purpose of journey in which the close call or crash occurred was examined, some gender differences did emerge. For example, females were less likely to have experienced the incident when commuting to work, but more likely than males to be on their way to pick up or drop off children from child care. This raises ques- tions of tiredness related to child-care responsibilities for the 26- to 40-year-old age group, the one most likely to have child-care responsibilities. It is arguable that further research into this possible connection would provide clearer data on this issue. Females were more likely to be closer to home and driving for a shorter time than males at the time of the close call or crash. This suggests there may be a differ- ent pattern and possible different underlying causes or incidents caused by driving when tired for females. As many of the interventions targeting driving when tired focus on longer trips and monotonous stretches of road, this finding suggests that females may be more likely to experience fatigue-related incidents closer to home. This in turn has important implications for targeting future interventions (for example advertising campaigns on the dangers of driving when fatigued). Examination of the symptoms of tiredness when driv- ing revealed that males and females experience similar symptoms. The most common symptoms reported by the current sample are similar to those commonly reported in the literature (20, 28) and include yawning (93%), difficulty concentrating (74%), changing position fre- quently (74%), eye blinks (70%), difficulty keeping eyes open (66%), and slower reaction times (57%); however, a slightly greater proportion of males reported continuing driving after feeling symptoms of tiredness. Further, males and females also reported similar use of various counter- measures for staying alert after experiencing symptoms of tiredness when driving. These were stopping the vehicle (60%), getting out of the car and stretching (35%), hav- ing something to eat or drink (34%), taking a nap (12%), and changing drivers (7%). Interestingly, while half of both males and females chose to continue driving, they also reported engaging in other activities to increase their alertness, such as winding down the car window (40%), turning on the radio (15%), increasing the volume of the radio (34%), or changing the temperature in the car (15%). Again these are similar to the common counter- measures reported in the literature (15). Given that the safest countermeasure is for a person to stop driving (2, 10), the fact that half the sample continued driving indi- cates more education in this area is necessary. In conclusion, the current investigation examined gender differences in the experience of driving when fatigued in a large gender-balanced sample of drivers and followed up in detail the 300 drivers who had experienced a close call or crash caused by driving when tired. The results indicated that there were no gender differences in the symptoms of tiredness experienced or in the types of countermeasures engaged in to combat tiredness. There were, however, some key gender differences in the purpose of the trip, time of driving, and trip distance from home when the incident occurred. These differences suggest that females were more likely to be driving short distances close to home when they experienced an incident. This has implications for aware- ness campaigns, which tend to focus more on fatigue as a long-distance issue. It is arguable that further research is required to examine the beliefs and attitudes of males and females in regard to what is considered risky practice when driving tired. Such research has the potential to pro- vide particularly useful information for the refinement and further development of appropriate countermeasures that better target this complex issue. RefeRences 1. Åkerstedt, T. 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