Are older drivers actually at higher risk of involvement in collisions resulting in deaths or non-fatal injuries among their passengers and other road users?

OBJECTIVES: With more older drivers on the road, public concern has been expressed about their impact on traffic safety. This study revisited the question of driver age in relation to the risks of older drivers and others sharing the road with them, including pedestrians, passengers in the same vehicle, and occupants of other vehicles. METHODS: Using United States federal data on fatal and non-fatal crashes, injury rates per driver were calculated for different types of road users. In addition, using data supplied by nine insurers, insurance claims per insured vehicle year were examined by driver age. The reference drivers were aged 30-59. RESULTS: For fatal crashes, older drivers' major impact on road users other than themselves was an increase in death rates among their passengers, who also tended to be elderly and thus more vulnerable to injuries (rate ratio (RR) for drivers aged 75+ 2.52; 95% confidence interval (CI) 2.39 to 2.66). For non-fatal crashes, drivers aged 75+ had a RR of 1.10 (95% CI 0.98 to 1.24) for involvement in collisions resulting in injuries to other passenger vehicles' occupants compared with 30-59 year old drivers. The oldest drivers (aged 85+) had significant increases in insurance claims for injuries to other road users in crashes in which they were deemed at fault (RR 1.8; 95% CI 1.71 to 1.89). CONCLUSIONS: These findings suggest that the oldest drivers, a group with low average annual mileage, do pose some increased risks to occupants of other vehicles, and pose the most serious risks to themselves and their passengers.

Drinking histories of fatally injured drivers.

CONTEXT: About 30% of drivers killed in crashes have high blood alcohol concentrations (BACs) of 0.10+ g/dl. There is a question about whether these drivers primarily are problem drinkers who chronically drink and drive-the so-called hard core drinking drivers. OBJECTIVE: To investigate drinking histories of fatally injured drivers in relation to their BACs. DESIGN AND PARTICIPANTS: Retrospective cohort study of 818 fatally injured drivers who were included in the 1993 National Mortality Followback Survey (a national sample of US deaths in which next of kin were interviewed) and whose BACs were recorded by the Fatality Analysis Reporting System, a census of US traffic deaths. MAIN OUTCOME MEASURE: Problem drinking indicators. RESULTS: At least one indicator of potential problem drinking, primarily heavy drinking, was reported for 68% of drivers with very high BACs (0.15+ g/dl), 41% with BACs of 0.10-0.14 g/dl, 32% with BACs of 0.01-0.09 g/dl, and 7% with zero BACs. Spouses provided more credible responses than other relatives: they were more likely to report at least occasional drinking and driving among deceased drivers with high BACs. For the most direct signs of problem drinking (described as a problem drinker during the last month of life or frequently driving after having five or more drinks), spousal reports suggested the prevalence of problem drinking among drivers with very high BACs was 22% (having both indicators), 32% (frequently driving after having five or more drinks), 44% (described as problem drinker), or 57% (having either indicator). CONCLUSIONS: Drivers with BACs of 0.10+ g/dl were far more likely than sober drivers to be described as having markers of problem drinking. However, many did not have indicators suggestive of problem drinking. In addition to programs focused on repeat offenders or problem drinkers, countermeasures such as sobriety checkpoints that target a broader spectrum of drinking drivers are appropriate.

Older driver involvements in police reported crashes and fatal crashes: trends and projections.

OBJECTIVES: Older drivers have become a larger part of the driving population and will continue to do so as the baby boomers reach retirement age. The purpose of this study was to identify the potential effects of this population increase on highway safety. METHODS: Driver involvement rates for all police reported crashes were calculated per capita, per licensed driver, and per vehicle-mile of travel for 1990 and 1995. Also, driver involvement rates for fatal crashes were calculated for 1983, 1990, and 1995. Based on current crash rates per licensed driver and estimates of the future number of licensed drivers, projections of crashes involving drivers aged 65 and older were made for years 2010, 2020, and 2030. RESULTS: Driver crash involvement rates per capita decreased with age, but fatal involvement rates per capita increased starting at age 70. The same pattern existed for involvement rates per licensed driver. For both all crashes and fatal crashes, involvement rates per mile driven increased appreciably at age 70. Using projections of population growth, it was estimated that for all ages there will be a 34% increase in the number of drivers involved in police reported crashes and a 39% increase in the number involved in fatal crashes between 1999 and 2030. In contrast, among older drivers, police reported crash involvements are expected to increase by 178% and fatal involvements may increase by 155% by 2030. Drivers aged 65 and older will account for more than half of the total increase in fatal crashes and about 40% of the expected increase in all crash involvements; they are expected to account for as much as 25% of total driver fatalities in 2030, compared with 14% presently. CONCLUSIONS: By most measures, older drivers are at less risk of being involved in police reported crashes but at higher risk of being in fatal crashes. Although any projections of future crash counts have inherent uncertainty, there is strong evidence that older drivers will make up a substantially larger proportion of drivers involved in fatal crashes by 2030 because of future increases in the proportion of the population aged 65 and older, and trends toward increased licensure rates and higher annual mileage among older persons. Countermeasures to reduce the anticipated death toll among older drivers should address the increased susceptibility to injury of older vehicle occupants in crashes.

Potential benefits of restrictions on the transport of teenage passengers by 16 and 17 year old drivers.

OBJECTIVES: The presence of passengers is associated with fatal motor vehicle crashes of teenage drivers. A restriction against newly licensed teenage drivers carrying passengers has been included in some, but not all, graduated licensing systems. The purpose of this study was to predict the net effects on all types of road users, including vehicle occupants and non-occupants, of possible prohibitions against 16-17 year old drivers carrying passengers. METHODS: Two national datasets, a census of fatal crashes and a sample of trips in the United States, were used to compute 1995 road user death rates. Potential effects of restrictions on drivers ages 16-17 carrying passengers younger than 20 were estimated, based on road user death rates and potential choices made by passengers who would have traveled with 16-17 year old drivers if there were no restrictions. RESULTS: There were 1,181 road user deaths in 1995 involving drivers ages 16-17 whose passengers were all younger than age 20. The predicted number of lives in the United States that would be saved annually ranges from 83 to 493 (corresponding to reductions of 7-42% in road user deaths) for drivers ages 16 and 17 combined. Similar percentages of reductions (8-44%) were predicted solely for 16 year old drivers. Assuming passenger restrictions would apply to all 16 year old drivers and at least one third of 17 year old drivers, an estimated 60-344 fewer deaths per year may occur if restrictions are mandated. CONCLUSIONS: Restrictions on carrying passengers younger than 20 should be considered for inclusion in graduated licensing systems. Even if fewer than half the drivers obey the restrictions, a substantial reduction in road user deaths would be expected. Further evaluation based on real world experience is needed to confirm their efficacy.

Carrying passengers as a risk factor for crashes fatal to 16- and 17-year-old drivers.

CONTEXT: Injuries from motor vehicle crashes are the leading cause of death among teenagers. Carrying passengers has been identified as a possible risk factor for these crashes. OBJECTIVE: To determine whether the presence of passengers is associated with an increased risk of crashes fatal to 16- and 17-year-old drivers and whether the risk varies by time of day and age and sex of drivers and passengers. DESIGN AND SETTING INCIDENCE: study of data from the Fatality Analysis Reporting System and General Estimates System (1992-1997), as well as the Nationwide Personal Transportation Survey (1995). SUBJECTS: Drivers aged 16 and 17 years who drove passenger cars, vans, or pickup trucks. MAIN OUTCOME MEASURE: Driver deaths per 10 million trips by number of passengers, driver age and sex, and time of day; and driver deaths per 1000 crashes by passenger age and sex. RESULTS: Compared with drivers of the same age without passengers, the relative risk of death per 10 million trips was 1.39 (95% confidence interval [CI], 1.24-1.55) for 16-year-old drivers with 1 passenger, 1.86 (95% CI, 1.56-2.20) for those with 2 passengers, and 2.82 (95% CI, 2.27-3.50) for those with 3 or more passengers. The relative risk of death was 1.48 (95% CI, 1.35-1.62) for 17-year-old drivers with 1 passenger, 2.58 (95% CI, 2.24-2.95) for those with 2 passengers, and 3.07 (95% CI, 2.50-3.77) for those with 3 or more passengers. The risk of death increased significantly for drivers transporting passengers irrespective of the time of day or sex of the driver, although male drivers were at greater risk. Driver deaths per 1000 crashes increased for 16- and 17-year-olds transporting male passengers or passengers younger than 30 years. CONCLUSION: Our data indicate that the risk of fatal injury for a 16- or 17-year-old driver increases with the number of passengers. This result supports inclusion of restrictions on carrying passengers in graduated licensing systems for young drivers.

Motor vehicle occupant deaths among Hispanic and black children and teenagers.

OBJECTIVE: To determine the risk of motor vehicle occupant deaths per unit of travel for Hispanic, non-Hispanic black, and non-Hispanic white children (aged 5-12 years) and teenagers (aged 13-19 years). DESIGN: Comparison of 1989 to 1993 motor vehicle occupant death rates of children and teenagers by race, ethnicity, and sex by using data on mortality from the National Center for Health Statistics, travel data from the 1990 Nationwide Personal Transportation Survey, and 1990 US census data. RESULTS: Among children 5 to 12 years old, race/ ethnicity differences per 100000 persons were unremarkable, but per billion vehicle-miles of travel, the rates were 14 for non-Hispanic blacks, 8 for Hispanics, and 5 for non-Hispanic whites. Among teenagers aged 13 to 19, the rates per 100000 persons were highest for non-Hispanic whites; however, the rates per billion vehicle-miles were 45 for Hispanics, 34 for non-Hispanic blacks, and 30 for non-Hispanic whites. Black and Hispanic male teenagers had substantially higher death rates per billion vehicle-miles of travel than either white male teenagers or female teenagers in any racial/ethnic group. CONCLUSIONS: Black and Hispanic children and teenagers are at higher risk of dying in motor vehicle crashes when they travel. Greater public health attention is needed to address these increased risks.

Seating positions and children's risk of dying in motor vehicle crashes.

OBJECTIVES: To determine the effects of seating position, combined with restraint use and airbag status, on children's risk of dying in crashes. METHODS: Using 1988-95 data from the United States Fatality Analysis Reporting System, risk of death was compared among front and rear seated passengers aged 12 and younger who were involved in fatal crashes for different categories of restraint use and in vehicles with and without passenger airbags. RESULTS: Restrained children in rear seats had the lowest risk of dying in fatal crashes. Among children seated in the rear, risk of death was reduced 35% in vehicles without any airbags, 31% in vehicles equipped only with driver airbags, and 46% in vehicles with passenger airbags. Both restrained and unrestrained children aged 0-12 were at lower risk of dying in rear seats. Rear seats also afforded additional protection to children aged 5-12 restrained only with lap belts compared with lap/shoulder belted children in front seats. Children were about 10-20% less likely to die in rear center than in rear outboard positions. CONCLUSIONS: Parents and others who transport children should be strongly encouraged to place infants and children in rear seats whether or not vehicles have airbags. Existing laws requiring restraint use by children should be strengthened and actively enforced.

A photograph-based study of the incidence of fatal truck underride crashes in Indiana.

Photographs were used to estimate the incidence of fatal crashes in which passenger vehicles underrode the fronts, sides and rears of large trucks in Indiana during 1993. The photographs were obtained for 98 of the 107 eligible fatal crashes between large trucks and passenger vehicles in 1993. A protocol was developed to judge the presence and extent of underride, the presence of intrusion into the passenger vehicle compartment, and the likelihood of death or serious injury if underride had been prevented. The incidence of fatal underride was compared with the incidence reported in the Fatality Analysis Reporting System (FARS), a census of fatal crashes on public roads in the U.S.A. For the same 107 fatal large truck-passenger vehicle crashes, the incidence of underride reported in FARS was much lower than in the photograph-based study: 6 versus 63%. Photographs contain details absent from police reports, the primary data source for FARS, and thus enable more complete identification of underride crashes. Preventing underride would have substantially reduced the likelihood of death or serious injury in ca 20% of the underride crashes.

Fatal crashes of passenger vehicles before and after adding antilock braking systems.

Fatal crash rates of passenger cars and vans were compared for the last model year before four-wheel antilock brakes were introduced and the first model year for which antilock brakes were standard equipment. Vehicles selected for analysis had no other significant design changes between the model years being compared, and the model years with and without antilocks were no more than two years apart. The overall fatal crash rates were similar for the two model years. However, the vehicles with antilocks were significantly more likely to be involved in crashes fatal to their own occupants, particularly single-vehicle crashes. Conversely, antilock vehicles were less likely to be involved in crashes fatal to occupants of other vehicles or nonoccupants (pedestrians, bicyclists). Overall, antilock brakes appear to have had little effect on fatal crash involvement. Further study is needed to better understand why fatality risk has increased for occupants of antilock vehicles.

Reductions in deaths in frontal crashes among right front passengers in vehicles equipped with passenger air bags.

CONTEXT: Virtually all new cars now are equipped with passenger air bags. Determining whether passenger air bags are saving lives is important, particularly because passenger air bags have caused some deaths among children and adults. OBJECTIVE: To assess the effectiveness of passenger air bags in reducing the risk of death in frontal crashes for right front passengers. DESIGN: Air bags are designed to protect occupants in frontal crashes. Using Fatality Analysis Reporting System data for calendar years 1992 through 1995, the relative frequency of right front passenger deaths in frontal vs nonfrontal fatal crashes was compared for cars with dual air bags and for cars with driver-only air bags. MAIN OUTCOME MEASURES: Odds of right front passengers dying in frontal compared with nonfrontal fatal crashes were computed for 1992 through 1995 model year cars with dual air bags and for cars with driver-only air bags. Percentage reductions in right front passenger deaths in dual air bag vehicles were estimated. RESULTS: Right front passenger fatalities were 18% lower than expected in frontal crashes of cars with dual air bags and 11% lower in all crashes. An estimated 73 fewer than expected right front passengers died in 1992 through 1995 model cars with dual air bags during 1992 through 1995. The risk of frontal crash death for right front passengers in cars with dual air bags was reduced 14% among those reported to be using belts and 23% among belt nonusers. Children younger than 10 years in cars with dual air bags had a 34% increased risk of dying in frontal crashes. CONCLUSIONS: Passenger air bags were associated with substantial reductions in fatalities among right front passengers in frontal crashes. However, more children are being killed than are being saved by air bags. Immediate countermeasures to reduce the dangers of air bags to children and adults are suggested.

Two-vehicle side impact crashes: the relationship of vehicle and crash characteristics to injury severity.

Injury type and severity among front outboard occupants of passenger vehicles struck in the side by another passenger vehicle and recorded in the United States National Accident Sampling System Crashworthiness Data System were examined in relation to the location of impact, the angle of impact, occupant gender and age, seat belt use, the weight and body style of the side-impacted vehicle, and the weight and body style of the striking vehicle. Elderly occupants were three times as likely as younger occupants in similar crashes to be seriously injured. Serious injuries were also more likely for occupants seated on the struck side and occupants of lightweight passenger vehicles. After accounting for vehicle weight differences, struck-side occupants of cars were still much more likely to be seriously injured than struck-side occupants of light trucks. However, among occupants seated on the side of the vehicle opposite the impact, the likelihood of serious injury was higher for those seated in light trucks.

Tractor-trailer crashes in Indiana: a case-control study of the role of truck configuration.

Studies of the crash experience of tractors pulling multiple trailers have reached different conclusions concerning the relationship of truck configuration to crash risk. A previous case-control study found a significant increase in crash risk for double-trailer trucks in the state of Washington. The present case-control study was done of tractor-trailers crashing on Indiana interstates during November 1989-March 1991. Controls were obtained for 25% of the crash sites and were all tractor-trailers passing the crash sites during a traffic observation session one to four weeks following a crash on the same day of the week for 30 minutes at the same time of day. Logistic regression identified day of week, time of day, urban/rural area, and specific highway as significant predictors of controls' truck configuration. This model was applied to the cases to estimate the expected number of double-trailer cases. For all crashes combined, no increased crash risk was observed for doubles (Standardized Crash Ratio (SCR) = 83). Doubles were significantly underinvolved in multiple-vehicle crashes (SCR = 74), crashes on dry roads (SCR = 61), and crashes on wet (other than snow, ice, or slush) roads (SCR = 54). Doubles were significantly overinvolved in crashes on roads with snow, ice, or slush (SCR = 153). Because truck configuration was highly associated with driver age and work operation attributes among trucks in crashes, the absence of control data on these potential confounders precluded definitive assessment of the intrinsic risk of multiple versus single-trailer vehicles.

Lower extremity injuries from motorcycle crashes: a common cause of preventable injury.

Lower extremity injuries are among the most common injuries sustained by motorcycle riders in crashes and often lead to extended and costly medical treatment and permanent disability. This study characterizes lower extremity injuries in a group of 700 motorcycle riders in crashes in Los Angeles County from July 1, 1988, through October 31, 1989. Motorcycle crash fatalities (n = 163) were identified through the Los Angeles County Coroner's office, and nonfatally injured riders (n = 537) were identified at four of the ten level I and level II trauma centers in the county. Lower extremity injuries were diagnosed in 301 (56%) of nonfatally injured and in 75 (46%) of fatally injured riders. Fractures were the most common lower extremity injury and were diagnosed in 52% and 42% of riders with nonfatal and fatal injuries, respectively. Over a third of all fractures were to the tibia or fibula. Drivers and passengers did not differ in their risk for lower extremity injuries. Multiple-vehicle collisions resulted in a higher risk of lower extremity injuries than did single-vehicle collisions. The highest risk for lower extremity fractures was observed among riders in broadside collisions in which another vehicle struck the motorcycle (risk ratio = 2.7). Modifications in vehicle design and rider apparel may prevent some lower extremity injuries in motorcycle crashes.

Long hours and fatigue: a survey of tractor-trailer drivers.

Fatigue and long driving hours have been implicated as risk factors in truck crashes. Under federal regulations, commercial drivers are permitted to drive no more than 10 hours before having an 8-hour break and cannot work more than 70 hours over an 8-day period. Several studies have suggested that violations of these rules are common. A survey of long haul tractor-trailer drivers was conducted to estimate what proportion of drivers report that they regularly violate the hours-of-service rules and to identify the drivers most likely to commit hours-of-service violations. During December 1990 through April 1991, a total of 1,249 drivers were interviewed at truck safety inspection stations, truck stops, and agricultural inspection stations in Connecticut, Florida, Oklahoma, and Oregon. In each state, interviews were conducted during varying periods of the day over the course of seven days at inspection stations. Overall, 89 percent of eligible drivers asked for interviews participated in the survey. According to self-reports, almost three-fourths of the respondents violate hours-of-service rules. About two-thirds of the drivers reported that they routinely drive or work more than the weekly maximum. A primary impetus for violating rules appears to be economic factors, including tight delivery schedules and low payment rates. Many other driver, job, and vehicle characteristics were significantly associated with being an hours-of-service violator. The high prevalence of hours-of-service violations among tractor-trailer drivers is a problem in need of urgent attention. Potential measures to reduce the prevalence of rules violations include more enforcement directed toward carriers, wider use of electronic recorders, and increasing the number of rest areas.

An analysis of lung cancer risk from exposure to hexavalent chromium.

Lung cancer risk in relation to airborne levels of hexavalent chromium was analyzed for chromium chemical production workers studied by Hayes, Lilienfeld, and Snell. Hayes et al [18] had observed statistically significant increases in lung cancer mortality among chromium chemical production workers hired during 1945-1959 and followed to mid-1977. A dose-response was observed by Hayes et al. in that long-term workers had a higher lung cancer risk than short-term workers. Concurrent exposure data for the study plant were abstracted from the records of a local health department. The usual air concentration of hexavalent chromium was estimated as 413 micrograms per cubic meter (micrograms/m3) during 1945-1949. Cumulative exposure estimates for individual workers could not be developed with available information. Instead, cumulative exposures in terms of micrograms/m3-years were estimated for groups of short-term workers and long-term workers (cumulative exposure = usual exposure level in micrograms/m3 X average length of exposure). For workers hired during 1945-1949, cumulative exposures were estimated as 670 and 3,647 micrograms/m3-years for short-term and long-term workers, respectively. Like most estimates based on historical data, these exposure estimates are subject to uncertainty. Nevertheless, these results suggest a potential excess risk of death from lung cancer among U.S. workers exposed to the current permissible exposure limit (PEL) for hexavalent chromium of 52 micrograms/m3 because such workers could accumulate exposures (micrograms/m3-years) similar to those associated with excess risk in Hayes et al's cohort. Moreover, many current workers are estimated to be exposed to levels above the PEL. Further exploration of the dose-response relationship for chromium carcinogenesis is indicated.