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Publication Number: FHWA-RD-99-078
Injuries to Pedestrians and Bicyclists: An Analysis Based on Hospital Emergency Department Data
CHAPTER 1. INTRODUCTION
Walking and bicycling are basic forms of transportation that are accessible to virtually all Americans. For many individuals--those too young or too old to drive, those who cannot afford to own a car, or those who simply choose not to own a car--walking or bicycling may be the only viable option for meeting personal transportation needs. Others may choose to park their automobile and walk or bicycle for fitness, health, economic, or environmental reasons, or simply for the enjoyment of being outdoors.
Over the past decade the Federal Government has taken unprecedented steps to increase support for bicycling and walking at the national as well as State and local levels. The National Bicycling and Walking Study, mandated by Congress in 1991, established two far-reaching goals: the first, to double the percentage of trips made by bicycling and walking, and the second, to reduce by 10 percent the number of bicyclists and pedestrians killed or injured in traffic crashes (FHWA, 1994). The Intermodal Surface Transportation Efficiency Act (ISTEA) of 1991, and its successor, the Transportation Equity Act for the 21st Century (TEA-21), have established the necessary funding opportunities and policies for achieving these goals.
The purpose of the current study was to broaden understanding about the safety of pedestrians and bicyclists. Traditionally, the U.S. Department of Transportation has relied on State motor vehicle crash data, based on reports completed by police and other law enforcement officers, as their primary source of information on events causing injury to pedestrians and bicyclists. While these data provide considerable information to help guide safety program and countermeasure development, they have often been referred to as "the tip of the iceberg" because they are limited almost entirely to motor vehicle-related events that occur on public roadways. Specifically, they exclude: (1) many bicycle-motor vehicle and pedestrian-motor vehicle crashes that occur in non-roadway locations such as parking lots, driveways, and sidewalks, and (2) bicycle and pedestrian falls that do not involve a motor vehicle, regardless of whether they occur on a roadway or in a non-roadway location. There is also evidence that even many pedestrian- and bicycle-motor vehicle collisions occurring on public roadways are not reported in police crash files.
The number of "missed" cases is substantial. More bicyclists are injured in bicycle-only events than in collisions with motor vehicles, and falls are a leading cause of injury for people of all ages and especially for the elderly. While a large percentage of falls occur on stairs and inside buildings or homes, pedestrians walking or jogging on sidewalks, stepping off curbs, and crossing roadways also fall, and this information is largely unreported.
The current study was conducted to provide a more accurate description of the entire spectrum of events causing injury to pedestrians and bicyclists, as an aid to more effective countermeasure and program development. Specifically, the study sought to:
The diagram in figure 1 identifies the four categories of pedestrian and bicyclist injury events addressed by this study, as defined by the location of the event with respect to the roadway and whether or not a motor vehicle was involved. Currently, most of what is known about collisions involving pedestrians and bicyclists falls into category A, since these are the events most likely to be reported by police and to appear on State motor vehicle crash files. However, with the more widespread use of External Cause of Injury or "E-codes" (U.S. Department of Health and Human Services, 1991) in hospital discharge and even some emergency department databases, more information is becoming available on the other categories of injury-causing events. The current report has combined information from police reports as well as medical sources to provide information with regard to all four quadrants of the matrix.
Figure 1. Types of events causing injury to pedestrians and bicyclists.
number of studies conducted in the United States as well as in Australia, New Zealand, and several European nations provide insight into non-roadway and non-motor vehicle-related events causing injury to pedestrians and bicyclists. Some of these studies address only a subset of the matrix shown in figure 1, for example, motor vehicle and non-motor vehicle-related bicycle crashes occurring on the roadway (quadrants A and C), or motor vehicle-related bicycle crashes occurring in both roadway and non-roadway locations (quadrants A and B). Other studies address all four areas of interest. Most of the studies have relied on a combination of police and hospital or emergency department data, sometimes supplemented by surveys or interviews. In some cases, direct comparisons have been drawn between databases.
The specific results of the studies vary widely; however, they all confirm that non-roadway and non-motor vehicle events pose significant threats to the safety of pedestrians and bicyclists. They also reveal that official road accident statistics, as determined from police crash reports, greatly underestimate the numbers of pedestrians and bicyclists being injured.
Foreign Research Studies
In Western Australia, hospital admission and police crash report data spanning the 15-month period October 1987-December 1988 were linked to produce a Road Injury Database (Rosman and Knuiman, 1994). Police crash reports were identified for 74 percent of the bicyclists and 69 percent of the pedestrians who had been admitted to a hospital for treatment of injuries resulting from (reportable) collisions with motor vehicles.
Examining the bicycle cases in more detail, it was found that of 842 bicycle-related hospital admissions, 76 percent were the result of a bicycle-only crash, 21 percent a bicycle-motor vehicle crash, and 4 percent were of unknown etiology (Piggott, 1994). In contrast, for the 1,066 police-reported bicycle crashes, only 8 percent were bicycle-only falls, 84 percent resulted from a collision with a motor vehicle, and 9 percent were unknown. Also, whereas 72 percent of the bicycle-motor vehicle cases were linked to the police crash files, only 5 percent of the bicycle-only crashes were linked. The authors conclude that "casualties from bicycle-only crashes are seriously underreported to the police." Information on the location of the injury events was not reported, although it was noted that the police-reported cases arose primarily from on-road collisions.
In a survey of hospitals carried out nationwide in Australia in 1990-1991, pedestrians comprised 15 percent of all admissions for road traffic injuries and bicyclists 9 percent (O'Connor and KPMG Peat Marwick, 1993). For this sample of hospital admissions, 94 percent of the pedestrians were injured in motor vehicle traffic accidents and 5 percent in motor vehicle non-traffic accidents, with just over 1 percent falling into a category of "other" road vehicle accidents. In contrast, 68 percent of the admitted bicyclists were injured in collisions with motor vehicles (63 percent on road, 5 percent off-road) and 32 percent in other, bicycle-only events. The authors of the report note that minor injuries requiring only emergency department treatment were especially likely to be underreported by police, with over twice as many cases appearing on emergency department files as on police files.
A New Zealand study revealed that nearly three-quarters (74 percent) of bicyclists admitted to a hospital for treatment during 1988 were injured on the roadway; however, only a third of these involved collisions with a motor vehicle (Collins, 1993). In addition to being injured on the roadway, bicyclists were also injured at home (9 percent) and at recreational or sport sites (4 percent). In 13 percent of the cases, the place of injury was noted as "other" or "unknown." Although representing only a third of hospital admissions, bicycle-motor vehicle collisions were much more likely to result in serious injury or death. In the 10-year period 1979-88, 238 bicyclists were fatally injured in New Zealand: 209 (88 percent) in collisions with a motor vehicle, and 228 (96 percent) on the roadway.
Studies using hospital discharge and emergency department data in Finland and Denmark also report high percentages of bicyclists being injured on public roadways, but many of these incidents did not involve a motor vehicle. In Finland, 80 percent of hospitalized bicyclists were injured in road-related accidents. Non-motor vehicle events accounted for 58-72 percent of the inpatients and 93 percent of the outpatients treated (Olkkonen, 1993). In Denmark, the results of a mail survey sent to 3,000 bicyclists treated at a large hospital emergency department revealed that 60 percent of the bicyclists had been injured in bicycle-only events and only 40 percent in collisions with other vehicles. Forty-two percent of the crashes had occurred on the roadway and an additional 44 percent on bicycle "tracks" or bicycle lanes along the roadway (Larsen, 1994).
When hospital databases have been compared to official road accident statistics, results have generally shown significantly fewer cases reported in the police-based files. In a New Zealand study, the ratio of official Ministry of Transport records for numbers of road accident victims compared to hospital admission figures was computed for various categories of road users over the 10-year period 1973-1982 (Morrison and Kjellstrom, 1987). Overall, the ratio of police-reported to hospital-reported cases was .66, but dropped to about .20 for bicyclists and .50 for pedestrians. For all categories of road users, the ratio declined over the 10-year study period.
European and British studies add to the range of findings. Maas and Harris (1984) reported ratios of .78 and .82 for numbers of police-reported versus hospital-reported pedestrian and bicyclist injuries, respectively, in The Netherlands during the early 1970s. In a subsequent article, Harris (1990) reported that these ratios had declined to less than 70 percent by the late 1980s. Using information gathered from a national telephone survey that was restricted to "reportable" accidents, but which included all levels of injury severity, not just hospital cases, Harris documented ratios of .11 for bicyclists and .25 for pedestrians. The .11 figure for bicyclists was the lowest of any of the examined road-user groups. In other research, a German study reported ratios of .30 for hospitalized bicyclists and .20 for bicyclists receiving outpatient treatment only (Hautzinger et al., 1993), while an early British study reported .24 for bicyclists receiving either inpatient or outpatient treatment (Bull and Roberts, 1973).
These studies in the foreign literature all point to the fact that official road accident statistics, based on police crash reports, underestimate injuries to pedestrians and bicyclists due to an underreporting of events that do not involve a motor vehicle, those that occur off the public roadway, and/or those that result in relatively less serious injuries. Part of this is due to the specific reportability requirements in effect. The international definition of a road traffic accident is an accident occurring or originating on a way or street open to public traffic, resulting in one or more persons being injured or killed, and involving at least one moving vehicle (United Nations, 1994). In many countries, however, only accidents involving a motor vehicle are reported. And regardless of specific reportability requirements, medical sources such as hospital emergency departments and hospital discharge databases consistently capture significantly larger populations of injured pedestrians and bicyclists.
U.S. Research Studies
The same trends observed abroad are reflected in the U.S. literature. In the United States, a traffic accident is officially defined as
"an accident that involved a motor vehicle that occurred on a public highway or road in the U.S. and that resulted in property damage or personal injury. Does not include accidents that have happened in a parking lot, in a driveway, on a private road, or in a foreign country." (USDOT, 1996, p. 189).
In practice, some States do report crashes that occur in public parking lots, driveways, or other "public vehicular areas," and even in private off-road locations in cases of serious injury. These cases, however, are generally excluded from national databases such as FARS (Fatal Accident Reporting System). Reporting practices vary from State to State. In a recent study of pedestrian and bicyclist crashes based on police crash reports from six States (California, Florida, Maryland, Minnesota, North Carolina, and Utah), the percentage of pedestrian crashes that were coded as occurring on private property varied from only 4 percent in California to 25 percent in Florida (Hunter et al., 1996). Walker (1993) noted that both Florida and Indiana reported "non-traffic" collisions; and although he concluded that the Indiana data were the most reliable, they were still found to capture less than half of all non-traffic events.
An early U.S. study that provided information on differences between official traffic accident databases and medical records was the Northeastern Ohio Trauma Study (Barancik and Fife, 1985). The study was based on a probability sampling of emergency department visits during 1977 to 42 hospitals in a 5-county region. Crash reports were identified for 55 percent of the emergency department patients treated for injuries received in a motor vehicle crash, and for 74 percent of the crash victims who were subsequently hospitalized. Separate information for pedestrians and bicyclists was not reported.
A number of emergency department studies have been carried out focusing on events causing injury to bicyclists. Generally, the studies have shown that a large percentage of bicyclist injuries treated in hospital emergency departments do not involve a motor vehicle. Actual percentages vary, depending on the particular setting of the study, but range from 13 percent in Minneapolis (Davis et al., 1980) to 50 percent in Boulder (Watts et al., 1986).
Analyzing special survey data collected by participating hospital emergency departments in North Carolina (10 hospitals in 1985 and 15 in 1986), Stutts et al. (1990) found that only 18 percent of the bicyclists were injured in collisions with motor vehicles. More than half (53 percent) of the injury events occurred in roadway locations, 17 percent in driveways, 6 percent on sidewalks, and 24 percent in other non-roadway locations such as parking lots, yards, or on private unpaved roads. While 60 percent of the bicycle injury cases involving a motor vehicle were linked to the North Carolina crash file, only 10 percent of all reported cases were linked.
One of the most comprehensive studies of injuries to bicyclists was carried out under the direction of the U.S. Consumer Product Safety Commission using 1991 National Electronic Injury Surveillance System (NEISS) data supplemented by followup telephone interviews with the injured bicyclists (Rodgers, 1995; Rodgers, 1993). The study also included analysis of bicycle-related deaths reported in FARS and a national random-digit dial telephone survey for gathering information on bicyclist exposure to crashes and injuries. NEISS is a representative sampling of U.S. hospital emergency departments. Only 10 percent of the bicycle injury cases reported through NEISS involved a collision or near collision with a moving motor vehicle. Just over half (53 percent) of the reported injuries occurred on a public roadway (mostly neighborhood streets), 5 percent on unpaved roads, 12 percent on sidewalks or playgrounds, 5 percent on trails, and less than 1 percent on bicycle paths. The remaining 25 percent were unaccounted for.
Baker et al. (1993) also examined NEISS data and reported the following locations for bicycle-related injuries reported by the system in 1987, 1989, and 1990: 34 percent on roadways, 28 percent at home (includes sidewalks and driveways), 6 percent at other public locations (schools, sport or recreational sites, etc.), and 32 percent unknown. Overall, 12 percent of the cases in this 3-year file were reported to involve a motor vehicle.
The Rodgers (1993; 1995) and Baker et al. (1993) studies also made comparisons between bicycle-related deaths reported by the National Center for Health Statistics (NCHS) based on death certificate data and the FARS data based on State police crash reports. Generally, these comparisons revealed that FARS contains 8-10 percent fewer bicycle-related deaths than does the NCHS database. This was attributed to the fact that approximately 10-14 percent of bicycle-related fatalities do not involve a motor vehicle and/or do not occur on public roadways. These findings are supported by earlier analyses carried out by the Centers for Disease Control and Prevention, showing that 90 percent of bicyclist fatalities involve motor vehicles and 86 percent occur on public roadways (Sacks et al., 1991) .
Pedestrian studies utilizing emergency department and other sources of data besides police crash reports have focused primarily on motor vehicle events involving young children. One of the earliest such studies examined fatally injured pedestrians ages 5 and under in Washington State. A review of coroner and other medical records showed that 58 percent of the reported fatalities resulted from non-traffic (i.e., non-roadway) events, with backing accidents in driveways being the single largest contributor (Brison et al., 1988). Agran et al. (1990) reported that 25 percent of injuries serious enough to require hospitalization in pedestrians under age 15 occurred in non-traffic events, while Walker (1993) reported that 20 percent of injuries to pedestrians under age 16 were due to non-traffic events. In general, the proportion of non-traffic events declined with increasing age in each of these studies. Using police reports on non-traffic injuries provided by the State of Indiana, Walker (1993) also developed a taxonomy of non-traffic pedestrian-motor vehicle crash types that included driveways, parking lots, alleys, and private streets.
In a national analysis of childhood injury deaths using NCHS mortality tapes, 16 percent of all fatalities for children ages 0-14 were found to result from pedestrian-motor vehicle collisions. Of these, 15 percent were non-traffic events occurring in parking lots, driveways, and other off-road locations (Waller et al., 1989).
One of the few studies to examine pedestrian accidents or falls not involving a motor vehicle was carried out by Eck and Simpson (1996). Noting the lack of available information to guide traffic engineers in developing effective countermeasures for such events, the authors explored the feasibility of using emergency department and emergency medical services records to supplement police accident report data. Although their approach did not prove practical for routine use, it did point out the importance of surface condition to pedestrian safety. Slippery surfaces from ice or snow and surface holes or openings were identified as being especially problematical for pedestrians (Eck and Simpson, 1996).
The literature review has included a broad range of studies carried out in the United States, Australia, New Zealand, The Netherlands, Denmark, and Germany. Although the varying methodologies, data sources, reporting requirements, and traffic environments make it difficult to draw consensus from the studies, the following summary statements are offered: