In 2000, 5,211 persons were killed and about 140,000 were injured in crashes involving large trucks. The purpose of this study is to explain the unsafe driver actions and conditions that are more likely in fatal crashes between cars and large trucks than in fatal crashes between cars and to identify strategies for educating motorists in safe driving practices that will help them avoid such crashes.

The study analyzed two-vehicle crashes in the 1995–98 Fatality Analysis Reporting System (FARS) database to compare car-car crashes with car-truck crashes. A limitation of the study is that it did not address nonfatal crashes, single-vehicle crashes, or crashes involving more than two vehicles; this is important to keep in mind because fatal and injury crashes are not similar in their causes or in the numbers of people they affect.

The research was conducted in three stages. The first stage sought to identify driving maneuvers or actions of cars and large trucks that have a higher chance of resulting in fatal car-truck collisions than fatal collisions with a similar vehicle. The second stage involved discerning patterns associated with these driving actions through a detailed examination of actual crash reports. The third stage involved exploring ways that the risks associated with the identified driving actions can be effectively communicated to motorists, paying special attention to the fit between study findings and potential instructional approaches.

The first stage of research involved an analysis of 94 driver-related factors. Using probability analysis techniques, the authors determined the likelihood of involvement for each factor based on the probability that the crash did or did not involve a truck. Information about the pre-crash actions of drivers was sought in national crash databases such as FARS, a national database of all vehicle crashes in the United States that result in at least one fatality. These data are based on such sources as police observations of the post-crash scene and the un-sworn testimony of surviving people and other witnesses. It was recognized that these sources have limitations. For instance, the physical evidence on which the police base their opinions may be conflicting or ambiguous, and people involved in a crash may be unable to remember information about the events before the crash.

Because of these uncertainties, it is not possible to directly assess pre-crash driver actions or to identify causal relationships between unsafe driving actions and crashes by simply tabulating crash data. It would be possible, however, to use an indirect data-analysis approach that would address the inherent uncertainty. Accordingly, the authors chose an analytical method that allowed them to estimate conditional probabilities.

The data file for analysis was created from FARS data for 1995–98 and consisted of all fatal crashes involving passenger vehicles (cars, station wagons, minivans, sport utility vehicles, and pickup trucks) and trucks (straight trucks and tractor-trailers) of more than 10,000 pounds gross vehicle weight. The analysis was limited to two-vehicle crashes, which accounted for about 86% of all multi-vehicle crashes involving only passenger vehicles and 82% of multi-vehicle crashes involving passenger vehicles and trucks. In this report, crashes between passenger vehicles, regardless of type, are referred to as “car-car crashes” and crashes between passenger vehicles and large trucks are referred to as “car-truck crashes.” The analysis file contained data on 35,244 fatal car-car crashes and 10,732 fatal car-truck crashes.

The results of the data analysis indicate that most driver factors are equally likely to be recorded for fatal car-truck crashes as for fatal car-car crashes. Moreover, drivers who get involved in fatal crashes probably drive in the same manner around trucks as they do around other cars. Indeed, in cases for which driver factors were recorded, five of the equally likely factors: failing to keep in lane, failing to yield right-of way, driving too fast for conditions or in excess of posted speed limit, failing to obey traffic control devices and laws, and inattentive comprised about 65% of reported unsafe car driver acts in both car-truck and car-car crashes. Four factors (out of 94) were found to be more likely to occur in fatal car-truck crashes than in fatal car-car crashes:

However, these four factors were recorded for only about 5% of the car-truck crashes.

The second stage of the research involved closely examining a random sample of 529 crashes for the top four factors differentiating fatal car-car and fatal car-truck crashes. Hard-copy materials—including original police accident reports, crash diagrams, and other crash-related information from the 1995–98 Trucks in Fatal Accidents records maintained by the Center for National Truck Statistics—were reviewed. The results of this analysis corroborate earlier studies of car-truck crashes showing that there are many more unsafe actions by car drivers than truck drivers. Also as expected, the crashes were much more dangerous for car drivers than truck drivers; car drivers accounted for nearly 98% of driver fatalities.

The results of the analysis also indicate that more than half of the fatal car-truck crashes in which a driver fell asleep were head-on crashes, and more than one-quarter of these occurred between 3 and 6 a.m. The results point to the use of alcohol or drugs and speeding as unsafe behaviors

among younger drivers for both cars and trucks involved in fatal car-truck crashes. Finally, the results are consistent with previous research; for instance:

The third stage of the research explored instructional strategies that could be used to teach motorists about the risks associated with the four unsafe driving actions and conditions identified in the first stage of the research. Effective educational efforts could include:

• Teaching motorists how to operate around large trucks, focusing on instruction on the four unsafe factors
• Creating an interactive World Wide Web site that educates drivers about the dangers associated with driving near trucks and allows them to test their knowledge
• Personal computer–based driving simulations, demonstrations, or computer games showing interactions between cars and large trucks

DISCUSSION OF FINDINGS

It is important to note again that, because of data limitations, this study looked only at fatal crashes. Nevertheless, the findings from this study are consistent with the findings from a study of unsafe driving acts of car drivers in the vicinity of trucks that was not limited to fatal crashes. It also needs to be noted that three of the four driver factors that were found in this study to be more likely to be associated with fatal car-truck crashes than with fatal car-car crashes were among those considered by safety experts to be dangerous and frequent near trucks.

A key finding of this study is that most of the 94 unsafe driver acts were about as likely in fatal car-truck crashes as in fatal car-car crashes. Therefore general safe driving practices are also relevant around large trucks. However, programs to educate drivers in safe practices need to emphasize that driving mistakes around trucks can have much more severe consequences.

This study’s examination of Fatality Analysis Reporting System records for two-vehicle fatal crashes from 1995 to 1998 showed that driver factors related to unsafe driver actions were much more likely to be recorded for car drivers than for truck drivers. Most of these driver factors were as likely to be recorded for car-car crashes as for car-truck crashes. In crashes for which factors were recorded, five driver factors (failing to keep in lane, driving too fast for conditions or in excess of posted speed limit, failing to yield right-of-way, failing to obey traffic control devices or laws, and inattentive) comprised about 65% of reported unsafe car driver acts in both car-truck and car-car crashes. However, using Bayesian analysis, four driver factors were found to be more likely in car-truck crashes than in car-car crashes:

These four driver factors were recorded in approximately 5% of the car-truck crashes. This finding indicates that although many driver actions and conditions are equally risky whether performed near cars or trucks, particular actions and conditions are riskier in car-truck than in car-car encounters. Given the unequal distribution of deaths for car and truck occupants, there is a potential for survivor bias in this study. In both the first and second stages of research, the vast majority of fatalities were car occupants; only a small percentage were truck occupants. Therefore, truck drivers and occupants had more influence on the police reports than car drivers and occupants. Fortunately, in many cases other witnesses and additional evidence (e.g., skid marks, impact sites) were also available to the crash investigators who were writing the reports.

It is important to note that this study looked only at fatal crashes. The uncertainty associated with trying to identify drivers’ actions in the national crash data set that contained nonfatal crashes was too large to make inclusion of nonfatal crashes feasible in this study. It is possible that the patterns of driver actions in nonfatal car-truck crashes are different than those for fatal car-truck crashes; a study by Blower (1998) tentatively concluded that this may be the case. Nevertheless, our findings from this study are consistent with the findings from a study of unsafe driving acts of car drivers in the vicinity of trucks that was not limited to fatal crashes (Stuster 1999). Stuster’s study included rating by truck drivers, crash investigators, and safety experts of the danger and frequency of various driving maneuvers performed by car drivers in the vicinity of trucks. His research found several unsafe driving acts performed in the vicinity of trucks to be among the most dangerous and frequent ones:

“Following too closely” and “changing lanes abruptly in front of a truck” match two of the driver factors found in our study, and the detailed review of the car-truck crashes conducted in the second stage of our research showed that many of the crashes in which the driver factor was recorded as “drowsy, sleepy, asleep, or fatigued” resulted in the vehicle driving left of center. It is interesting to note that three of the four driver factors found in our study to more likely be associated with fatal car-truck crashes than with fatal car-car crashes were also among those considered by safety experts to be dangerous and frequent in the vicinity of trucks.

Programs to promote safe driving near large trucks could educate drivers about the risks of driving near large trucks by starting with the top five unsafe driver actions. Educational materials might include standard brochures and brief films. However, it could be argued on the basis of research and experience that brochures and films generally produce little behavioral change. More effective would be an interactive World Wide Web site that educates drivers about the dangers of driving near trucks and allows them to test their knowledge.

Perhaps the best technology to enable car drivers to change their behavior when they drive near trucks (although impractical in many situations) would be to enable them to get closed-track or on-the-road driving experience with a large truck to see what it is like. Personal computer–based driving simulations, demonstrations, or computer games based on real-world scenarios in which car drivers must accomplish particular maneuvers near trucks and at the same time react to various maneuvers from trucks appear to present a reasonable balance between potential for dissemination and behavior change. However, before such programs can be developed it is important to understand the conditions that will encourage drivers to use them.

A key finding from the first stage of this study is that the profile of causes and characteristics for fatal car-truck crashes are very similar to those for fatal car-car crashes. This finding is further supported by our second-stage review of original police accident reports, crash diagrams, and witness statements for a sample of more than 500 fatal car-truck crashes with at least one of the four driver factors that showed age and gender effects consistent with broader crash risks. These included alcohol and speeding among younger car drivers and problems with negotiating intersections (e.g., failure to yield the right of way) among older car drivers. This finding implies that effective programs to promote safe driving in general can also be used to promote safe driving near trucks. However, these programs need to emphasize that though the same safe-driving techniques generally apply to driving around both cars and trucks, making some mistakes around trucks can have much more severe consequences.