Crash risk factors for interstate large trucks in North Carolina
Teoh, Eric R.; Carter, Daniel L.; Smith, Sarah; McCartt, Anne T.
Insurance Institute for Highway Safety
Provide an updated examination of risk factors for large truck involvements in crashes resulting in injury or death.
A matched case-control study was conducted in North Carolina of large trucks operated by interstate carriers. Cases were defined as trucks involved in crashes resulting in fatal or non-fatal injury, and one control truck was matched on the basis of location, weekday, time of day, and truck type. The matched-pair odds ratio provided an estimate of the effect of various driver, vehicle, or carrier factors.
Out-of-service (OOS) brake violations tripled the risk of crashing; any OOS vehicle defect increased crash risk by 362 percent. Higher historical crash rates (fatal, injury, or all crashes) of the carrier were associated with increased risk of crashing. Operating on a short-haul exemption increased crash risk by 383 percent. Antilock braking systems reduced crash risk by 65 percent. All of these results were statistically significant at the 95 percent confidence level. Other safety technologies also showed estimated benefits, although not statistically significant.
With the exception of the finding that short-haul exemption is associated with increased crash risk, results largely bolster what is currently known about large truck crash risk and reinforce current enforcement practices. Results also suggest vehicle safety technologies can be important in lowering crash risk. This means that as safety technology continues to penetrate the fleet, whether from voluntary usage or government mandates, reductions in large truck crashes may be achieved.
Results imply that increased enforcement and use of crash avoidance technologies can improve the large truck crash problem.
Crash avoidance potential of four large truck technologies
Jermakian, Jessica S.
Accident Analysis and Prevention
The objective of this paper was to estimate the maximum potential large truck crash reductions in the United States associated with each of four crash avoidance technologies: side view assist, forward collision warning/mitigation, lane departure warning/prevention, and vehicle stability control. Estimates accounted for limitations of current systems.
Crash records were extracted from the 2004–08 files of the National Automotive Sampling System General Estimates System (NASS GES) and the Fatality Analysis Reporting System (FARS). Crash descriptors such as location of damage on the vehicle, road characteristics, time of day, and precrash maneuvers were reviewed to determine whether the information or action provided by each technology potentially could have prevented the crash.
Of the four technologies, side view assist had the greatest potential for preventing large truck crashes of any severity; the technology is potentially applicable to 39,000 crashes in the United States each year, including 2000 serious and moderate injury crashes and 79 fatal crashes. Vehicle stability control is another promising technology, with the potential to prevent or mitigate up to 31,000 crashes per year including more serious crashes — up to 7000 moderate-to-serious injury crashes and 439 fatal crashes per year. Vehicle stability control could prevent or mitigate up to 20 and 11 percent of moderate-to-serious injury and fatal large truck crashes, respectively. Forward collision warning has the potential to prevent as many as 31,000 crashes per year, including 3000 serious and moderate injury crashes and 115 fatal crashes. Finally, 10,000 large truck crashes annually were relevant to lane departure warning/prevention systems. Of these, 1000 involved serious and moderate injuries and 247 involved fatal injuries.
There is great potential effectiveness for truck-based crash avoidance systems. However, it is yet to be determined how drivers will interact with the systems. Actual effectiveness of crash avoidance systems will not be known until sufficient real-world experience has been gained.
Occupant deaths in large truck crashes in the United States: 25 years of experience
Lyman, Stephen; Braver, Elisa R.
Accident Analysis and Prevention
There is public concern about the magnitude of the problem of large truck crashes in the US. Fatalities in large truck crashes have not declined much; however, more large trucks are driving more miles than ever before while fatalities per mile driven have dropped substantially. This study examined how the public health burden of large truck crashes versus the risk per unit of travel has changed over 25 years. The present study focused on the US vehicle occupants in fatal crashes involving a large truck during 1975-1999. Occupant fatalities per 100000 population, per 10000 licensed drivers, per 10000 registered trucks and per 100 million vehicle-miles of travel (VMT) were calculated to determine trends in occupant deaths in large truck crashes. In 1999, large truck crashes resulted in 3916 occupant deaths in passenger vehicles and 747 in large trucks. Passenger vehicle occupant deaths in large truck crashes per 100000 population have increased somewhat since 1975 (1.28 in 1975 and 1.44 in 1999). There have been appreciable declines in occupant deaths per truck VMT since 1975, but the percentage reduction has been greater for occupants of large trucks (67%) than for passenger vehicle occupants (43%). However, truck drivers are at elevated risk of dying relative to their numbers in the workforce. Overall large truck involvements in fatal crashes per truck VMT decreased more than passenger vehicle involvements per passenger VMT (PVMT; 68% versus 33% decreases for single-vehicle crashes and 43% versus 23% for multiple-vehicle crashes). Large truck involvement in fatal crashes has dropped substantially when measured per unit of travel, but the public health burden of large truck crashes, as measured by deaths per 100000 population, has not improved over time because of the large increase in truck mileage. Research is needed on measures to better protect both occupants of large trucks and passenger vehicle occupants colliding with them.
Toll road crashes of commercial and passenger motor vehicles
Braver, Elisa R.; Solomon, Mark G.; Preusser, David F.
Accident Analysis and Prevention
Revenue-collection data from toll roads allow for accurate estimates of miles driven by vehicle type and, when combined with crash data, valid estimates of crash involvements per mile driven. Data on vehicle-miles traveled and collisions were obtained from toll road authorities in Florida. Kansas, and New York. In addition, state crash files and published vehicle-miles of travel were obtained for toll roads in Illinois. Indiana, Ohio, and Pennsylvania. Large commercial motor vehicles were significantly underinvolved in single-vehicle crashes on all state toll roads. In five states, commercial motor vehicles were significantly overinvolved in multiple-vehicle crashes relative to passenger vehicles; the exceptions were Kansas, where they had significantly lower multiple-vehicle involvement rates, and Indiana. where there were no significant differences in multiple-vehicle involvements by vehicle type. The risk of commercial motor vehicle involvement in multiple-vehicle crashes resulting in deaths or serious injuries was double that of passenger vehicles in the two states (Ohio and Pennsylvania) that identified serious injuries. Whether crash rates, on toll roads of commercial motor vehicles are higher or lower than those of passenger vehicles appears to depend on the type of crash, specific toll road. and traffic density.
Tractor-trailer crashes in Indiana: a case-control study of the role of truck configuration
Braver, Elisa R.; Zador, Paul L.; Thum, Denise; Mitter, Eric L.; Baum, Herbert M.; Vilardo, Frank J.
Accident Analysis and Prevention
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.
Major types of fatal crashes between large trucks and cars
Braver, Elisa R.; Preusser, David F.; Williams, Allan F.; Weinstein, Helen B.
Proceedings of 40th Annual Conference of the Association for the Advancement of Automotive Medicine
More than 3,700 passenger vehicle occupants died in crashes involving large trucks in 1994. To better understand how and why these crashes occur, crash type analysis was applied to a 50% systematic sample of the 3,178 fatal large truck-passenger vehicle crashes in 1993 from the Fatal Accident Reporting System. Odds ratios (OR) and their 95% confidence intervals were estimated to identify associated roadway, environmental, vehicular, and driver factors. The two most common crash types, "oncoming" (head-on) and "ran traffic control" (vehicle required to stop or yield fails to do so), accounted for 61% of all crashes; these crash types typically occur on undivided roads (ORs = 7.1 and 1.4, respectively). Slippery road conditions (OR = 2.4), hills (OR = 1.6), and curves (OR = 5.3) were significant risk factors for "oncoming" crashes. The next three most common crash types were "stop/stopping" (stopped or slowing vehicle is struck from behind), "run down" (vehicle strikes another moving in same direction at unimpeded speed), and "lane change" (vehicle moves into an already occupied lane); these crashes were significantly more likely to occur on divided roads (ORs on undivided roads = 0.27, 0.09, and 0.02, respectively). Reduced light conditions were a significant risk factor for "stop/stopping" (OR = 2.0) and "run down" (OR = 4.8) crashes. Countermeasures to reduce the risk of truck-car crashes include modifying the structure of trucks to make them less likely to inflict injuries in collisions with other vehicles, making trucks more conspicuous, improving truck brakes, and improving enforcement of existing highway safety laws.
A study of fatal crashes involving pedestrians and trucks in four cities
Retting, Richard A.
Journal of Safety Research
Crashes between pedestrians and large trucks, which were fatal to the pedestrians and occurred during 1986–90 in four cities, were studied using Fatal Accident Reporting System (FARS) data. Comparisons were made with similar fatal crashes between pedestrians and vehicles other than large trucks. Data for truck crashes were supplemented with narratives and diagrams from police reports to develop a crash typology. Pedestrian fatalities in crashes with trucks were more likely than those involving other vehicles to occur at intersections, at traffic signals, during daylight hours, and to involve older pedestrians. Fifty-one percent of pedestrians killed in collisions with trucks were over the age of 60, compared with 37% killed in collisions with other vehicles. Obstruction of truck driver visibility, caused by the design of truck cabs, appears to be a major contributing factor in crashes at intersections. The data suggest that greater emphasis should be placed on separating pedestrians and trucks at intersections and on designing truck cabs to improve driver visibility.
A review of fatal injuries to pedestrians induced by urban truck crashes
Retting, Richard A.
Proceedings of the 37th Annual Conference of the Association for the Advancement of Automotive Medicine
Crashes between pedestrians and trucks, which were fatal to the pedestrians and occurred during 1986-90, were studied. Police reports were used to develop a crash typology. Comparisons were made with crashes between pedestrians and other vehicles. Pedestrian fatalities in crashes with trucks were more likely to occur at intersections, at traffic signals, during daylight, and to involve older pedestrians. Most fatal injuries were to the head and chest regions. Obstruction of driver visibility, caused by truck design, appears to be a factor in crashes at intersections. Emphasis should be placed on separating pedestrians and trucks and on designing trucks to improve visibility.
Discussion on "A comparison of accident rates for two truck configurations" by Jovanis, Chang, and Zalsnch
Hertz, Robin P.; Zador, Paul L.
Transportation Research Record 1249
Defective equipment and tractor-trailer crash involvement
Jones, Ian S.; Stein, Howard S.
Accident Analysis and Prevention
The role of defective equipment in large truck crashes on interstate highways in Washington State was investigated using a case-control study design. For each large truck involved in a crash, three trucks were randomly selected from the traffic stream at the same time and place as the crash, but one week later both crash and comparison trucks were inspected by Commercial Vehicle Enforcement officers of the Washington State Patrol. The effects of truck equipment condition, truck operating characteristics (carrier type, carrier operation, and truck load), and driver characteristics (driver age, hours of driving) on crash involvement were analyzed by comparing their relative frequency among crash-involved and comparison sample tractor-trailers. A logistic regression model was used to estimate the adjusted odds ratio for each factor. Overall, 77% of tractor-trailers in crashes and 66% of those not involved in crashes had defective equipment warranting a citation. Forty-one percent in crashes had defective equipment warranting taking the truck out of service, and 31% not in crashes had these defects. Brake defects were the most common type and were found in 56% of tractor-trailers in crashes; steering equipment defects were found in 21%. The relative risk of crash involvement for trucks with brake defects was about one and one-half times that for trucks without brake defects. For trucks with steering defects, the relative risk of crash involvement was at least twice that for trucks with steering defects, the relative risk of crash involvement was at least twice that for trucks without defects, and the risk increased substantially for trucks with out-of-service steering defects.
Crash involvement of large trucks by configuration: a case-control study
Stein, Howard S.; Jones, Ian S.
American Journal of Public Health
For a two-year period, large truck crashes on the interstate system in Washington State were investigated using a case-control method. For each large truck involved in a crash, three trucks were randomly selected for inspection from the traffic stream at the same time and place as the crash but one week later. The effects of truck and driver characteristics on crashes were assessed by comparing their relative frequency among the crash-involved and comparison sample trucks. Double trailer trucks were consistently overinvolved in crashes by a factor of two to three in both single and multiple vehicle crashes. Single unit trucks pulling trailers also were overinvolved. Doubles also had a higher frequency of jackknifing compared to tractor-trailers. The substantial overinvolvement of doubles in crashes was found regardless of driver age, hours of driving, cargo weight, or type of fleet. Younger drivers, long hours of driving, and operating empty trucks were also associated with higher crash involvement.
Comparison of passenger vehicle and truck crash rates on toll roads
Preusser, David F.; Stein, Howard S.
The mileage based crash rates of tractor-trailer trucks compared to passenger vehicles have been widely debated. Valid comparisons have been difficult because the two vehicle types accumulate much of their mileage on different types of roads and traffic environments. To address this issue, crash rates were calculated for passenger vehicles and tractor-trailers operating on the same roads where mileage estimates for the two vehicle types could be obtained. Toll roads that routinely collect vehicle mileage data by type of vehicle used for this study were the ticket-controlled portions of the New York State Thruway, New Jersey Turnpike, Kansas Turnpike, and Florida Turnpike. The results show that the per mile crash involvement rate for tractor-trailers is greater than the rate for passenger vehicles on each of the four turnpikes. Tractor-trailers also had a higher multiple vehicle crash involvement rate and a higher fatal crash involvement rate.
The benefits of energy absorbing structures to reduce the agressivity of heavy trucks in collisions
Jones, Ian S.
Proceedings of the 11th International Technical Conference on Experimental Safety Vehicles
Because of the large weight differences that now exist between heavy trucks and cars, car occupants are at risk of serious injury when they collide with large trucks. However, although there is little that can be done to reduce this disparity in weight, it is possible to modify trucks so that the effects of the impact between a heavy truck and a car could be lessened. This paper estimates the effects of modifying the fronts of heavy trucks to incorporate crushable structures with stiffness characteristics similar to the fronts of cars. Equations of motion are developed that show that equipping trucks with crushable zones would increase the deceleration distance available to car occupants in car-truck collisions by 40 percent and reduce the average deceleration to restrained occupants by a factor of 1.4. A method is provided that transposes this reduction in acceleration to a reduction in fatality risk using Fatal Accident Reporting System data for 1977-1985. An example is given that shows a crushable zone could reduce the likelihood of fatal injury to car occupants by as much as 33 percent.
The dangerous giants of the American highway
Business and Society Review
Influence of truck size and weight on highway crashes
Jones, Ian S.; Stein, Howard S.; Zador, Paul L.
Research Note 105
May 1984 (revised) March 1983
Large trucks account for six percent of the nation's highway crashes and 12 percent of all fatal crashes. On a per mile basis, trucks are less frequently involved in crashes than cars, but trucks are involved in twice as many fatal crashes. The proportion of fatal crashes involving trucks has remained constant since 1977, while the relative risk of death for car occupants in crashes with large trucks has steadily increased from 23:1 to 31:1. Combination trucks - tractor semitrailers or tractor semitrailers plus trailers - have almost twice the crash rate of straight trucks, and a fatal crash involvement rate three times that of cars. Twin trailer configurations - tractor semitrailers plus trailers - have higher crash involvement rates than tractor semitrailers. However, the exposure of different truck types varies in terms of miles traveled, kinds of highways used, and times of day operated, and the influence of these variations on crash rates has not been adequately quantified. Until detailed exposure data are collected, comparisons of truck crash experience by configuration will be limited.
Fatally injured truck drivers
Karlson, Trudy A.; Baker, Susan P.; Morton, Bert F.
Proceedings of the 21st Annual Conference of the American Association for Automotive Medicine
Autopsy findings on 68 fatally injured truck drivers were reviewed to ascertain severe injuries sustained upon impact with the occupant compartments. Injures of the head, neck, chest, and abdomen in drivers of vans, pickups, and heavy trucks are discussed with some suggestions as to possible mechanisms. Findings suggest that particular attention is needed to prevent steering assembly injuries of the chest and abdomen in drivers of heavy trucks and pickups, injuries of the cervical spinal column in drivers of pickups, and head injuries of the drivers of vans. It is urged that existing knowledge of crash dynamics and occupant protection be applied to the prevention of injuries to truck occupants.
Reducing deaths and injuries in crashes involving heavy trucks: ten strategies
Baker, Susan P.
Insurance Institute for Highway Safety
Alcohol in fatal tractor trailer crashes
Baker, Susan P.
Proceedings of the 19th Annual Conference of the American Association for Automotive Medicine
A series of 150 fatal crashes involving tractor trailers was studied retrospectively. Twenty-five tractor trailer drivers and 63 drivers of other vehicles died and were tested for alcohol. About one-third in each group had blood alcohol concentrations of 0.10% by weight or more. Of 17 tractor trailer drivers apparently responsible for crashes, 8 had illegal alcohol concentrations (0.10% or more). Only 2% of the surviving drivers were charged with driving while intoxicated or impaired. Recommendations include implementation of the federal standard calling for quantitative tests for alcohol, where practicable, on all drivers (including surviving drivers) in crashes fatal to other persons.
Fatal tractor trailer crashes: considerations in setting relevant standards
Baker, Susan P.; Wong, Jackson C.; Masemore, William C.
Proceedings of the Fourth International Congress on Automotive Safety
A series of 150 fatal crashes involving tractor-trailers was examined retrospectively. There were 19 single vehicle and 131 multi-vehicle crashes. Tractor-trailers were more likely to be the following vehicle in rear-end collisions, except for those that occured on an upgrade. Vehicle failures were noted for 15 tractor-trailers, compared with two of the vehicles they collided with. There were no deaths to tractor-trailer occupants following collision with a car unelss in addtion to striking the car there was another major impact. Underride occurred in 9% of the collisions with cars. Of 41 fatally injured occupants of tractor-trailers, at least 8 were ejected and 8 trapped in the tractors (other than by fires) for prolonged periods. Post-crash fired occurred in 8% of the crashes. The paper discusses the need for adequate braking, improved ability to maintain speed, and weight limits that do not negate loss reduction benefits achieved uner other regulations. Other recommendations include improved protection against side- and rear-underride by cars and better crash protection for occupants of truck tractors. To discourage present tendencies to sacrifice the safety of truck occupants in the interest of greater payloads, limits for length and weight should be xclusive of the tractor.
The role of alcohol in collisions involving trucks and the fatally injured
Waller, Julian A.
Archives of Environmental Health
The role of alcohol was studied in collisions in which drivers of large trucks and pickup trucks were involved either as fatally injured or surviving drivers. Drivers of large trucks almost always were the survivors, usually were not at fault, and probably had not been drinking in any of their crashes. The fatally injured drivers or pedestrians who initiated the crashes commonly had high blood alcohol concentrations. In contrast, drivers of pickup trucks more often were fatally injured in these crashes, frequently were responsible for their crashes, and usually had high blood concentrations. A comparison of blood alcohol concentrations and police assessments of drinking showed that an assessment that a person had not been drinking was correct in only 48% of cases in which the person or his vehicle was responsible for the crash, but in all cases reviewed where he was not responsible.