Research on Women's Issues in Transportation, Volume 1: Conference Overview and Plenary Papers (2006)

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39 Women’s Issues in Highway Safety Summary of the Literature Susan A. Ferguson and Keli A. Braitman, Insurance Institute for Highway Safety A review of research literature on passenger vehicle safety that focuses on gender differences is provided. Around the world women are licensed and driving more than in the past. The result is that more women are dying in crashes, although more men than women still die in crashes every year because men drive more miles than women and tend to take more risks (speed, driving under the influence of alcohol, less frequent use of seat belts). Men’s crashes are often more severe than women’s, but when crash severity is controlled for, women are more likely to be killed or injured. Evidence suggests that for the most part vehicle features designed to reduce injuries (e.g., seat belts and airbags) are as effective in protecting women as men. Sometimes they are more effective. For example, improvements to head restraints may be reduc- ing neck injury more for women than men. There also have been changes in crash testing; dummies represent- ing shorter women are beginning to be used. One area that has received limited attention is the safety of preg- nant women and their fetuses. The development of a pregnant dummy has been under way for years, and research using both real and computer-simulated preg- nant dummies is exploring how factors such as seat belts, airbags, and crash severity affect a pregnant mother and fetus in a crash. As more women drive into their later years and drive more miles, it will be important to eval- uate changes in crash characteristics over time as a func- tion of age and sex as well as the types of injuries that women and men sustain. The overinvolvement of men, especially youngmen, in motor vehicle crashes has been recognizedfor a long time. However, the issue of gender dif- ferences in highway safety has not received as much attention as age differences. With the realization that more women are dying in motor vehicle crashes than before (Cerrelli 1994), the safety of female drivers has been the subject of reports in both Australia and the United Kingdom (Attewell 1998; Ginpil and Attewell 1994; Hill and Mackay 1997; Over 1998; UK Depart- ment for Transport 2005). Major changes in women’s roles in the United States during the past several decades have affected their use of private motor vehicles (Rosenbloom 1996). Women’s activity in the labor force, type of employment, and earn- ings are now more equal to those of men (Hayghe 1996). Society as a whole has seen staggering growth in the dependence on automobiles, suburbanization of homes and jobs, number of single-adult and single-person households, and aging of the population, among other changes (Rosenbloom 1996). The result is that women are licensed and driving more than ever before, although still far less than men (Mayhew et al. 2003). It also has been suggested that women are driving more aggressively than they have in the past (Kostyniuk et al. 1996), which is contributing to the higher crash rates. What is known about gender differences in motor vehicle safety is summarized here. The focus is on pas- senger vehicle safety rather than on bicycle, motorcycle, or pedestrian safety. In comparison of men and women,

it is important to note that although some physiological differences may account for these trends, variations in crash rates and injuries have a lot to do with when, where, how, and what women drive, as well as how much they drive. Any discussion of gender differences also should rec- ognize the considerable variations as a function of driver age (Evans 2004). As discussed by Rosenbloom in her plenary presentation at this conference, driving by women often is fundamentally different from that of men inasmuch as their roles as mothers and care providers affect their trips. Research also suggests that women drive older, smaller vehicles than men, which increases the likelihood of injury in the event of a crash (UK Department for Transport 2005; U.S. Department of Transportation 2003). Changing demographics should be recognized. Older women today are licensed less often than men, but this situation is likely to change. Today’s baby boomers, more of whom have held licenses for much of their adult lives, likely will drive more than their predecessors as they age. Gender differences in crash and injury rates are dis- cussed here and how these patterns have changed over time. Also examined is whether the injuries women sus- tain in a given crash (e.g., frontal, side) are different in type or frequency from those of men. To the extent pos- sible, the effectiveness of various vehicle systems designed to reduce injuries in crashes is addressed for men versus women. The general manner in which people drive and the extent to which they take risks also are examined as a function of sex. A topic that has not received much attention but has a clear gender compo- nent is the safety of pregnant women and their fetuses in motor vehicle crashes. Studies were identified through several sources, including the Transportation Research Information Ser- vices (TRIS) database, Internet searches (e.g., www.Google.com, www.Nexis.com), proceedings of sci- entific conferences, and backward referencing. MOTOR VEHICLE CRASH RATES Only about one-third of all U.S. motor vehicle crash deaths in 2003 involved women. Women accounted for about a third of driver and pedestrian deaths, nearly half of passenger vehicle deaths, and about 10% of bicycle and motorcycle deaths [Insurance Institute for Highway Safety (IIHS) 2005a]. Gender differences in the rates of crash involvement depend on several factors including injury outcome (fatal, nonfatal injury, or all), how rates are mea- sured (per capita, per driver, or per distance driven), and driver age. When only fatal crashes are examined, it becomes clear that men have higher rates of driver involvement than women. In the United States, the rate among men is about three times the rate among women per 10,000 licensed drivers (Li et al. 1998; Mayhew et al. 2003). Men also have about twice the rate of fatal crashes when measured per 1,000 crashes (Li et al. 1998) or per mile traveled (Mayhew et al. 2003). In Australia, rates of fatal crash involvement per licensed driver and per kilometer traveled show essentially the same gender disparities as those in the United States (Attewell 1998). The picture is somewhat different when all crashes are examined. In U.S. police-reported crashes, which include predominantly nonfatal crashes, men were one-third more likely than women to crash when measured per 1,000 licensed drivers. However, per million miles trav- eled, women were 12% more likely than men to crash. Controlling for miles traveled does not necessarily con- trol for gender differences in where vehicles are driven, for example, differences in the amount of urban or rural travel [unpublished analyses of data from U.S. Depart- ment of Transportation’s General Estimates System, driver licensing data, and National Household Travel Survey (NHTS) 2005]. Similar results were found in western Australia. Crash rates were higher for men when measured per capita and per licensed driver but higher for women when measured per kilometer traveled (Ryan et al. 1998). Comparing results across studies is difficult because researchers often select different crash categories to analyze (e.g., injury crashes, police-reported crashes, severe crashes). Still, studies conducted during the past decade in Canada (Chipman et al. 1993), Jordan (Al-Balbissi 2003), New Zealand (Wylie 1995), and Western Australia (Ryan et al. 1998) indicate that men generally have higher crash rates than women when rates are measured per licensed driver and per capita, particularly for fatal and severe crashes. Gender differences in crash rates vary by driver age. In the United States in 2003, crash involvements per 1,000 licensed drivers were higher for men than for women. This finding was true in all crashes and in fatal ones. For fatal crashes, the gender difference was par- ticularly large among younger and older drivers (Figure 1). In 2001–2002, the latest year for which updated mileage data are available, driver fatal crash involve- ments per 100 million miles traveled were higher for men than for women through age 65. Gender differ- ences in fatal crashes per 100 million miles traveled were greatest among people aged 16 to 24. When all crashes are considered, however, driver crash involve- ments per million miles sometimes were higher among men, sometimes among women (Figure 2) [unpublished analyses of data from U.S. Department of Transporta- tion Fatality Analysis Reporting System (FARS), Gen- eral Estimates System, driver licensing data, and NHTS, 2005]. 40 RESEARCH ON WOMEN’S ISSUES IN TRANSPORTATION

RISK PERCEPTION AND RISKY DRIVING A number of studies have shown that men rate the crash risk of driving situations lower than do women. Trankle et al. (1990) asked male and female drivers of various ages (18 to 21, 25 to 45, 65 to 75) to classify traffic scenes in terms of risk. Young men tended to rate crash risk lower relative to young women, older men, and older women. In a similar study Mundt et al. (1992) eval- uated the effect of sex on risk perception of a crash in various scenarios among young college students. Women consistently rated crash likelihood higher compared with men, including when the effects of alcohol on driving were factored in. Men also tend to rate their driving abilities more highly. Drivers of all ages tend to rate their driving as better than average, but men do so to a greater extent than women (Delhomme 1991; Sivak et al. 1989; Williams 2003; Williams et al. 1995). A national survey of U.S. drivers found that men were more likely than women to compare themselves favorably with other drivers and to rate themselves highly on driving skill and safety (Williams 2003; Williams et al. 1995). Men also adopt riskier driving styles than women. They are less likely to use seat belts and more likely to speed, follow too closely, and drive after drinking. U.S. surveys in 2003 reported belt use rates among front-seat occupants of 84% (women) and 77% (men) (Glassbren- ner 2004). Belt use also was higher among women in an observational study of Michigan drivers during 1984–1996. However, belt use during this 12-year period increased at similar rates among men and women (Kostyniuk et al. 1996). In 2003 a higher percentage of male drivers who died in passenger vehicle crashes were unrestrained compared with female drivers (unpublished analyses of data from FARS, 2005). Men also are more likely than women to speed. A study of U.S. fatal crashes in 2003 found that the relative 41WOMEN’S ISSUES IN HIGHWAY SAFETY 0 20 40 60 80 100 16 17 18 19 20– 25– 30– 35– 40– 45– 50– 55– 60– 65– 70– 75– 80– 85+ Driver age Males Females Males Females 0 50 100 150 200 250 16 17 18 19 20– 25– 30– 35– 40– 45– 50– 55– 60– 65– 70– 75– 80– 85+ Driver age (a) (b) FIGURE 1 (a) Driver fatal crash involvements per 100,000 licensed drivers, 2003; (b) driver crash involvements per 1,000 licensed drivers, 2003. 0 3 6 9 12 15 18 0 5 10 15 20 25 30Males Females Males Females 16 17 18 19 20– 25– 30– 35– 40– 45– 50– 55– 60– 65– 70– 75– 80– 85+ Driver age 16 17 18 19 20– 25– 30– 35– 40– 45– 50– 55– 60– 65– 70– 75– 80– 85+ Driver age (a) (b) FIGURE 2 (a) Driver fatal crash involvements per 100 million miles traveled, 2001–2002; (b) driver crash involvements per million miles traveled, 2001–2002.

proportion of speed-related crashes to all crashes was highest among 15- to 20-year-old men (National High- way Traffic Safety Administration 2004a). The propor- tions were higher for men than for women across all age groups, although the magnitude of the gender gap nar- rowed with increasing age. Similarly, a study of young drivers in Finland during 1978–1991 found that driving too fast for the road conditions was a factor in 68% of men’s fatal crashes but only 31% of those of women (Laapotti and Keskinen 1998). An analysis of speed-related crashes in Michigan in 1994 showed that crash rates were higher for men (seven speed-related crashes per 1,000 licensed drivers) than for women (three crashes) (Kostyniuk et al. 1996). How- ever, from 1987 to 1994 crash rates decreased by 8% for men but increased 12% for women. The increase among women was due largely to a 16% increase in speed- related crashes among young female drivers. So although men are more likely than women to speed (Kostyniuk et al. 1996; Laapotti and Keskinen 1998; National High- way Traffic Safety Administration 2004a), there is some indication that more young women are speeding than in previous years (Kostyniuk et al. 1996). In the United States in 2003, the percentage of fatally injured drivers who were impaired by alcohol was more than twice as high among men as among women (38% compared with 18%) (IIHS 2005b). Similarly, a 1996 U.S. national breath test survey of drivers on weekend nights indicated a higher percentage of men driving under the influence of alcohol compared with women (Voas et al. 1998). Other studies confirm this pattern. In fatal two-car crashes in the United States in 1986, Per- neger and Smith (1991) found the odds of being at fault was 21% higher for men compared with women. How- ever, in crashes in which alcohol was not involved the odds of being at fault were 17% lower for men com- pared with women. In a study of young drivers in Fin- land during 1978–1991, Laapotti and Keskinen (1998) found that alcohol was involved in 34% of men’s crashes but in only 7% of women’s. Alcohol-impaired driving has decreased among fatally injured drivers, both male and female. From 1982 to 2003, the estimated reductions in crash deaths of alcohol- impaired drivers of passenger vehicles was 32% (men) and 45% (women) (IIHS 2005a). However, findings of the 1996 national breath test survey indicated that more women were driving on weekend nights than in 1986 and somewhat more of them had been drinking (Voas et al. 1998). In contrast, the percentage of alcohol-impaired male drivers decreased slightly from 1986 to 1996. Single-vehicle nighttime crashes are sometimes used as a proxy for alcohol-involved crashes. A study of such crashes in Michigan in 1994 showed higher crash rates for men (14 crashes per 1,000 licensed drivers) than for women (6 crashes) (Kostyniuk et al. 1996). However, compared with 1987 the rates had decreased 7% for men and increased 11% for women. This finding supports the notion that in alcohol-involved nighttime crashes the gen- der gap may be narrowing (Voas et al. 1998). Following other vehicles too closely is another aspect of risky driving that more often is reported among men. Evans and Wasielewski (1983) reported that in both Michigan and Ontario men generally drove with shorter following distances than women. Similarly, in a 1994 study of Michigan drivers Kostyniuk et al. (1996) found that the rates of rear-end collisions (presumably indica- tive of following distance) were higher for men (12 crashes per 1,000 licensed drivers) than for women (8 crashes). Compared with 1987, these rates had increased about 10% among women but only 1% among men. As discussed earlier, men are more likely than women to speed, drive while impaired by alcohol, and drive or ride without using a seat belt. These behaviors often coexist. Belt use tends to be lower among drivers under the influence of alcohol than among those who are sober (National Highway Traffic Safety Administration 2004b), and alcohol-impaired drivers also are more likely to drive at excessive speeds (National Highway Traffic Safety Administration 2004a). All three of these factors independently increase fatality risk, and their combination may lead to even higher risks among men compared with women. The tendency for men to drive more dangerously than women has notable effects. As mentioned earlier, women have slightly higher rates of crashes per million miles traveled, but men’s crashes are more likely to be severe or fatal (Li et al. 1998). Men’s risky driving also may have an effect on the type of crashes they experi- ence. Laapotti and Keskinen (1998) examined differ- ences in loss-of-control and non-loss-of-control fatal crashes among young, novice drivers in Finland during 1987–1991. Driving under the influence of alcohol dif- ferentiated loss-of-control crashes from other fatal crashes among young men but not women; driving under the influence played a role in 49% of men’s loss- of-control crashes but only 6% of their other fatal crashes. Among women, alcohol played a role in 7% of both their loss-of-control and other fatal crashes. These data clearly indicate that men engage in more hazardous driving compared with women, but there is some limited evidence that the gender gap may be nar- rowing among the youngest drivers. Young women in Michigan are more likely to speed than in the past (Kostyniuk et al. 1996). Other data suggest that women are more likely to drive on weekend nights (Voas et al. 1998) and to drive under the influence of alcohol (Voas et al. 1998). The gender gap in nighttime crashes involv- ing alcohol also may be narrowing (Kostyniuk et al. 1996; Voas et al. 1998). However, further research is needed to confirm these findings. 42 RESEARCH ON WOMEN’S ISSUES IN TRANSPORTATION

INJURY PROPENSITY IN CRASHES OF SAME SEVERITY A paradox exists when motor vehicle injury and fatality rates among men and women are examined. Women are more prone to injury in a crash, but men sustain most of the serious injuries and fatalities because men tend to drive more miles than women and their crashes tend to be more severe (Li et al. 1998). Researchers who con- trolled for crash severity found that injury risk is higher among women than men, although this gender differ- ence tends to decrease with age (Bedard et al. 2002; Evans 2001a; Evans 2001b; Evans and Gerrish 2001). When factors such as age, blood alcohol content, loca- tion of impact, restraint use, and speed are controlled for, the odds of fatal injury in a crash are 54% higher for women compared with men (Bedard et al. 2002). This effect is limited mostly to younger women. Proportion- ally fewer older women are fatally injured compared with men of the same age. Using a double-pair comparison and other methods to control for crash severity, researchers estimated a 22% to 31% increase in the fatality risk for a 20-year-old woman relative to a 20-year-old man (Evans 2001a; Evans 2001b; Evans and Gerrish 2001). Evans (2001a) also showed that fatality risk increases at a slightly greater compound rate with age for men compared with women. In general, though, from the preteen years through the late 50s, women are more likely than men to sustain fatal injuries in similar crashes. These findings are seen regardless of vehicle type, seating position, occu- pant restraint use, and other factors such as calendar year, and suggest that the gender difference in injury propensity may be due to greater fragility among women than men. TRENDS IN CRASHES AND DRIVING EXPOSURE As mentioned earlier, men historically have sustained more deaths and injuries in motor vehicle crashes, but women have been catching up. The U.S. government began keeping motor vehicle fatality records in 1975, and since then there have been a number of changes among male and female drivers in terms of licensure, mileage, and fatalities. From 1975 to 2001, driver deaths increased 80% among women but decreased 2% among men (IIHS 2005a). Driver fatalities per capita declined 26% among men during 1975–2002 while increasing 36% among women; the rate was still higher among men. Also during this period the number of licensed driv- ers increased at a faster rate for women compared with men; they now are equivalent. Fatalities per 100,000 licensed drivers remain higher for men than for women, but this gender difference is narrowing because the rates are decreasing for both men and women, although faster among men (34% among men since 1975, 5% among women) (unpublished analyses of data from Census Bureau, FARS, and driver licensing data, 2005). Given the increasing deaths among women, some have hypothesized that women may be driving more aggres- sively than they used to. Kostyniuk et al. (1996) provided some support for this hypothesis in a study of a limited group of young drivers in Michigan. However, when one considers women drivers of all ages combined and total miles traveled is controlled for, there is no evidence of an increase in fatal crash rates among women compared with men. Overall, men drove 65% more miles than women in 2001; yet total annual miles driven have increased more for women than men (159% for women since 1975, 60% for men). When this difference in mileage is controlled for, driver fatalities per 100 million miles traveled have decreased by similar amounts in both groups (45% for men and 48% for women during 1977–2001) (unpub- lished analyses of data from FARS and NHTS, 2005). These data support the notion that the increase in fatalities among women drivers is due to increased exposure, not an increase in risky driving practices. Trends in licensure, mileage data, and fatalities per distance driven in Australia mirror the trends in the United States. Attewell (1998) reported that from 1991 to 1995 the number of licensed drivers in Australia increased more among women (15%) than among men (6%). In addition, average annual kilometers driven declined 6% among men but increased 14% among women. Similar to trends observed in the United States, fatalities per distance driven decreased by similar amounts during 1976–1995 for both men and women. CRASH INJURY PATTERNS AND EFFECTIVENESS OF VEHICLE COUNTERMEASURES There is some evidence that the distribution of injuries by body region, as well as the frequency of injuries, dif- fers among men and women in the same type of crash. For example, with 1992–1994 frontal crash data from the United Kingdom, Mackay and Hassan (2000) reported that female car occupants restrained in front seats sustained head, thorax, and lower limb injuries in lower-severity crashes than men did. Other researchers have reported gender differences in the likelihood of tho- rax injuries. On the basis of cadaver tests, Foret-Bruno (cited in Evans 2001b) found that women had a 20% greater risk of thorax injury compared with men. In a U.K. sample of serious injuries resulting from frontal crashes, Welsh and Lenard (2001) reported that restrained female drivers, who were far more likely than male drivers to be injured, had higher incidences of spine and leg injuries, whereas men sustained more head 43WOMEN’S ISSUES IN HIGHWAY SAFETY

injuries. These data also revealed that women have a higher propensity for skeletal chest injuries at lower crash severities. In a sample of police-reported tow-away crashes in the United States, Crandall et al. (1996) found that female drivers and shorter occupants were at higher risk of lower limb injuries in head-on crashes. A follow-up investigation showed that this risk was due not only to occupant height but also to the types of shoes women sometimes wear; that is, high heels could affect foot and ankle stability and thereby increase the risk of lower limb injuries. It also has been reported that a higher propor- tion of female drivers than men sustain head, face, or neck injuries in near-side side impacts (IIHS 2003). Ample evidence indicates that women are more likely than men to sustain neck injuries in rear-end crashes (Chapline et al. 2000; Farmer et al. 1999; O’Neill et al. 1972; States and Balcerak 1973). In the 1970s, O’Neill et al. reported insurance claim rates for neck injury among drivers of cars with head restraints: 29% of women and 22% of men reported such injuries. In the 1990s, Farmer et al. found that driver neck injury claim rates were remarkably similar to those reported in the 1970s: 30% of women and 23% of men reported such injuries. Chap- line et al. (2000) surveyed drivers who had been in police- reported rear-end crashes, finding that 45% of the women and 28% of the men reported neck pain. CRASHWORTHINESS COUNTERMEASURES Front and Side Impact Airbags Because women are more prone to injury than men in crashes of given severities, women may be differentially affected by countermeasures aimed at reducing injuries. Frontal airbags, particularly first-generation airbags, resulted in more airbag-related deaths and injuries to women than to men. The energy required to inflate frontal airbags quickly to protect occupants in crashes sometimes can cause injury as well. Many airbag-related deaths involve occupants who were unbelted or improp- erly belted. Improperly restrained occupants are likely to move forward during a frontal crash, especially if there is hard braking or evasive maneuvers, putting them on top of or extremely close to airbags when they deploy. Women are especially vulnerable because they are shorter and sit closer to airbags. Of the 84 drivers who died as a result of airbag deployments in low-severity crashes, 64 (three-fourths) were women. Although the loss of life due to frontal airbag deploy- ments has been small compared with the number of lives saved, the overrepresentation of women in airbag-related deaths warrants examination of airbag effectiveness as a function of sex. In more severe frontal crashes, Cum- mings et al. (2002) reported that airbags reduced the risk of fatal injury about as much for women (12%) as for men (6%), although the authors did not report whether this difference was significant. In an analysis of the lifesaving benefits of side airbags, Braver and Kyrychenko (2004) examined crashes in which vehicles were struck on the driver side. Separate analyses were conducted for airbags that protect only the torso and those that protect both the torso and the head. Side airbags that provide both torso and head pro- tection reduced the risk of driver death by 44% for men and 33% for women, although this difference was not significant. Airbags that protect only the torso reduced the risk of death by 21% for men but had no effect for women. Seat Belts Kahane (2000) reported that seat belts reduce the risk of death by the same amount for both men and women (45% when riding in passenger cars). Head Restraints Improvements to head restraints may reduce the risk of neck injury more for women than for men. Farmer et al. (1999) examined the relationship between head restraint position and neck injury in rear crashes. Vehicles with head restraints rated good by IIHS were compared with those rated acceptable, marginal, and poor. Ratings are based on the position of restraints relative to the head of an average-size man; restraints that are closer to the top and back of the head earn better ratings because they are expected to protect more of the population. After con- trolling for the effects of driver age, direction of impact, crash location, and crash severity, the researchers found that both male and female drivers of cars with head restraints rated good were 24% less likely than drivers of cars with poor-rated restraints to sustain neck injuries in rear impacts. Significant reductions in reported neck injury also were shown for female drivers of cars with restraints rated acceptable compared with those rated poor. No similar reductions were found for male drivers. However, the restraints rated acceptable probably pro- vide protection for more women. Similar findings were reported by Chapline et al. (2000). In this study, head restraints were rated on the basis of measurements of the position of a driver’s head relative to the restraint’s position at the time of the crash. Head restraint position was significantly related to the rate of reported neck injury among women but not among men. Estimated reductions in neck injury rates for drivers with adequately positioned head restraints 44 RESEARCH ON WOMEN’S ISSUES IN TRANSPORTATION

relative to poorly positioned ones were similar for men and women. However, fewer men in the study had ade- quately positioned head restraints, so for them the effect was not significant. One additional study reports that women benefit more from better-positioned or improved head restraints. Farmer et al. (2003) examined automobile insurance claims, finding that restraints with improved geometry reduced driver neck injury rates by about 37% for women but had little effect for men. Similarly, new head restraint designs such as active restraints that move up and closer to people’s heads in rear-end crashes reduced driver neck injury rates by 55% for women (sig- nificant) and 31% for men (not significant). PREGNANCY AND MOTOR VEHICLE SAFETY An understanding of pregnancy and motor vehicle safety has been hampered by the lack of relevant data. Crash databases do not consistently note whether women were pregnant. Moreover, fetal death certificates do not record maternal crash involvement as a possible cause of death, and such information typically is absent from injury surveillance systems (Weiss 2001). Approximately 4 million women each year in the United States become pregnant, including about 10% of women ages 15 to 45 (Klinich et al. 2005). With more women in the workplace and many of them driving to work until late in their pregnancies, many women and their unborn children are at risk of crash injuries. Such injuries include placental abruption, uterine rupture or laceration, and fetal injury or death. Uterine ruptures and lacerations are fairly rare, an estimated 1% of preg- nant trauma cases (Pearlman et al. 1990a). These injuries are sustained almost exclusively by women during the latter stages of pregnancy. As the uterus grows it extends beyond the pelvic cavity, and because it is filled with fluid, additional loading can more easily lead to rupture. Weiss et al. (2001) conducted a retrospective study of fetal injury deaths (20 weeks’ gestation and older) due to trauma in 16 states during 1995–1997. Information regarding crash involvement was not coded on fetal death certificates, so data were extracted from the narra- tives. Motor vehicle crashes were the leading cause of traumatic fetal injury death, representing about 82% of the fatalities. Extrapolating these data to the general U.S. population, the authors estimated 143 fetal deaths per year. Noting that this was conservative given a variety of factors such as the likely underreporting of fetal death by about 50%, the authors said that the estimated number of fetal deaths from crashes could be as high as 370 per year. Other crash consequences to unborn children include fetal injury or premature birth. The accompany- ing complications of early emergency births can lead to long-term negative consequences for children, but esti- mates of the frequency of these adverse outcomes are unavailable. Placental abruption, which involves the premature separation of the placenta from the uterus and disruption of the supply of oxygen and nutrients to the fetus, is the leading injury mechanism for fetal death in motor vehicle crashes (Lane 1989; Pearlman et al. 2000; Weiss 2001). It also is the most frequent pregnancy-related injury, esti- mated to occur in 1% to 5% of minor crashes and 20% to 50% of severe crashes (Klinich et al. 1998). Placental abruption is most likely to occur in severe crashes (Reis et al. 2000) but can occur with little or no injury to the mother (Agran et al. 1987; Pearlman et al. 2000). Crash severity has been shown to be the strongest pre- dictor of fetal outcome. In a study of 42 crashes involving pregnant occupants, Klinich et al. (2000) found that fetal loss or major fetal complications occured in all of the crashes classified as severe (>48 km/h) regardless of restraint use or airbag deployment. In low- and moderate- severity crashes, the highest percentages of positive out- comes occurred among those restrained with either a three-point lap-shoulder belt alone or a three-point belt plus airbag. From the same data, Pearlman et al. (2000) reported that adverse fetal outcomes are less likely to occur with proper restraint use than without. The authors concluded that high-severity crashes are likely to lead to poor fetal outcome, but proper restraint use in low- and moderate-severity crashes can decrease the likelihood of fetal death and other complications. Results of additional studies using real-world and crash test data support the findings that restraint use as well as proper restraint use reduce the likelihood of fetal injury or death. The definition of “proper” varies some- what among researchers but generally is considered to include a lap belt positioned low and beneath the abdomen and a shoulder belt positioned between the breasts. Klinich et al. (1998) examined 120 crashes involving pregnant occupants, largely extracted from a literature review, and found that in the majority of cases (48 of 69) of placental abruption the pregnant occupant was unrestrained. In crash tests with a pregnant dummy, Pearlman and Viano (1996) found that proper belt place- ment, with or without airbag deployment, resulted in the lowest injury ratings compared with improper belt place- ment or no restraints. In fact, the authors found a three- to fourfold increase in force transmission through the uterus when the lap belt was improperly positioned across the pregnant abdomen rather than beneath it. A major limitation of this study was that the design of the pregnant dummy did not allow adequate study of pla- cental abruption, which is widely noted as the most com- mon injury mechanism of fetal death. Hyde et al. (2003) studied fetal deaths in police-reported crashes in Utah and found that compared with restrained pregnant 45WOMEN’S ISSUES IN HIGHWAY SAFETY

women, those who were unrestrained were at greater risk of having low-birth-weight babies and maternal bleeding. They were nearly three times more likely to experience a fetal death. More research is under way to understand better the specifics of how seat belts affect the uterus, the uteroplacental interface, and the fetus during a crash. Researchers at Volvo (Jordan 2004), Vir- ginia Polytechnic Institute and State University (Stitzel et al. 2003) and the University of Michigan Transportation Research Institute (Rupp et al. 2001) are conducting crash tests with real and computer-simulated pregnant dummies. In addition to crash severity and restraint use, fetal outcome also is related to maternal injury. Both Klinich et al. (2000) and Ikossi et al. (2005) reported that adverse fetal outcome was greater when maternal injury was high. However, fetal injury or death has been found to result with little or no maternal trauma, and outcomes such as placental abruption were not necessarily pre- dictable on the basis of maternal injury (Pearlman et al. 1990b). Less is known about the effects of airbag deployment on fetal outcome. Risk of fetal head injury due to airbag deployment may increase when occupants are unre- strained or improperly restrained. In 15 mile per hour tests with unrestrained crash dummies, Pearlman and Viano (1996) reported an increase in the risk of fetal head injury with airbag deployment. However, when occupants were properly restrained, there was little evi- dence of increased risk. Uterine force was relatively low in all test conditions in which an airbag deployed, with and without belt use, especially compared with test con- ditions with improper belt placement and no airbag. In real-world crashes involving pregnant women, Klinich et al. (1998, 2000) reported that positive fetal outcomes were highest among restrained occupants, with or with- out airbag deployment. Klinich et al. (2000) tentatively concluded that airbags may have a positive effect on fetal outcome but cautioned that this finding was based on a small sample. One issue among pregnant drivers is the proximity of the abdomen to the steering wheel. Regard- less of airbag presence, impact with the steering wheel can result in injury. In a study of the anthropometry of pregnant women and their seating positions, researchers not surprisingly found that the distance between the steering wheel and abdomen decreased with increasing gestational age. As pregnancy progressed, subjects did not move farther away from the steering wheels because of the need to operate the pedals (Klinich et al. 1998). RESTRAINT USE DURING PREGNANCY A few studies have addressed the issue of seat belt use during pregnancy. Ikossi et al. (2005) studied 1,195 injured pregnant women who were admitted to trauma centers during 1994–2001, finding reported belt use of only 66%. Surveys examining restraint use among preg- nant women during prenatal visits to medical centers or health departments have determined that women need to be better informed of the benefits of proper restraint use during pregnancy and how to achieve such use. Self- reports of restraint use among survey respondents range from 42% (Schiff et al. 1992) to 98% (Johnson and Pring 2000). Restraint use also was found to be higher during pregnancy than prior to it. Restraint use report- edly increased by 9% (Tyroch et al. 1999) to 61% (Mc- Gwin et al. 2004) during pregnancy. However, 11% (Pearlman and Phillips 1996) to approximately half of those sampled (Johnson and Pring 2000; Tyroch et al. 1999) were unable to identify proper belt placement. Pearlman and Phillips reported that 23% of survey respondents said they “rarely or never” wore restraints; 11% of women who said they wore restraints also said they positioned them over the uterus. Thus, one-third of pregnant women in the sample did not routinely wear restraints or wore them improperly. CONCLUSIONS There is ample evidence from the United States and around the world that women’s driving habits are chang- ing as more women transition into the workplace and become more reliant on motor vehicles. In many coun- tries more women are holding licenses and driving more miles than in the past. Over time this increase will mean additional older women on the road. These changes have resulted in more driver deaths and injuries among women, leading people to question whether women are driving less safely than before. Looking at women drivers as a group, researchers have found little evidence of more aggressive driving (Mayhew et al. 2003), although one limited study suggests that this type of driving may be occurring among the youngest drivers (Kostyniuk et al. 1996). More research is needed to address this question. Men, especially younger men, still lead in risky driving behaviors. They are more likely to ride unrestrained and more likely to speed, tailgate, and drive when impaired by alcohol. These risky behaviors result in higher fatal crash rates among men however the rates are measured because the crashes men typically have are more serious. When all police-reported crashes are examined, the pic- ture changes somewhat. Crash rates per licensed driver are higher for men, but per mile driven the rates are some- what higher for women. Women generally tend to rate safety as a more important consideration than men (Fer- guson and Williams 1996). However, all other things being equal, women are more vulnerable to crash injuries. That is, when crash severity is controlled for, women are 46 RESEARCH ON WOMEN’S ISSUES IN TRANSPORTATION

more likely to be injured and die, although this gap nar- rows among older drivers. Pregnancy has not garnered a lot of attention among highway safety researchers. One of the challenges has been estimating the magnitude of the problem because crash databases do not consistently code relevant infor- mation about maternal condition or injuries to the fetus. Another challenge in evaluating the efficacy of counter- measures or countermeasure opportunities is the limited availability of a dummy that represents a pregnant woman and fetus. The development of a pregnant dummy has been under way for some years. Additional research is being conducted with real and computer-sim- ulated pregnant dummies to better understand how seat belts affect the uterus and the fetus in a crash. Research suggests that pregnant women in crashes are better pro- tected by properly positioned seat belts. However, edu- cation is needed to ensure that pregnant women are aware of what to do to ensure proper belt positioning. Research should continue to explore the effects of airbag deployment in crashes involving pregnant women at var- ious gestational stages. Historically, government crash tests and tests con- ducted by consumer groups have used dummies that rep- resent an average-size man, but there is growing recognition that in some cases it may make sense to use dummies representing women and children (of course, child restraint testing has always used child dummies). Until quite recently the U.S. government’s high-speed frontal crash tests used only 50th-percentile male dum- mies. However, since it has been recognized that women and children are more vulnerable to airbag-related injuries, manufacturers have been required to conduct additional tests using dummies that represent both short women and children. These tests, required since Septem- ber 2003, are designed to minimize the potential harm from airbags while at the same time maintaining their lifesaving benefits. Recently the Insurance Institute for Highway Safety began evaluating the side impact performance of passen- ger vehicles in a crash test that represents what happens when the driver side of a vehicle is struck by a pickup or sport utility vehicle. The institute uses a side impact dummy representing a small woman or 12-year-old because the head of this shorter dummy is in the window area where people’s heads are more vulnerable to being struck by the front end of a vehicle in a real-world impact (IIHS 2003). Using the smaller dummies ensures that vehicle design changes to improve side impact crash test performance are tailored to protect small as well as large occupants. For example, crash tests to date have demon- strated the overriding importance of side airbags that protect the head. No vehicles without this technology have received a good rating. However, in one crash test the head airbag was too small—it only partially covered the window—to prevent the dummy’s head from being struck by the hood of the striking vehicle. Evaluations of countermeasure effectiveness often include analyses as a function of sex. Research to date suggests that countermeasures such as seat belts, airbags, and head restraints typically work as well or better for women. However, the experience with frontal airbag- related deaths suggests that care should be taken to include tests to ensure there are no deleterious side effects. Is there more that can be done to better protect women in vehicles? It is likely that the amount of driving by women, especially older women, will increase. But there is little to suggest that women are becoming riskier drivers. Additional research is needed to evaluate changes in crash characteristics over time as a function of age and sex. 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