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There are 8.22 million single-unit trucks1 registered in the United States, which travel more than 110.7 billion miles each year. Although single-unit trucks comprise three percent of registered motor vehicles and four percent of miles traveled, they are involved in nine percent of fatalities among passenger vehicle occupants in multivehicle crashes. Crashes involving single-unit trucks and passenger vehicles pose a hazard to passenger vehicle occupants due to differences in weight, bumper height, and vehicle stiffness.2 The National Transportation Safety Board (NTSB) undertook this study because of concerns about the safety record of single-unit trucks and an interest in identifying countermeasures to address the risks posed by these vehicles. Single-unit trucks are excluded from some safety rules applicable to tractor-trailers. Single-unit trucks do not have to meet the requirements for improved rear underride guards (mandatory in 1998 for new trailers) and conspicuity treatments to enhance visibility (mandatory in 1993 for new trailers; in 1997 for new truck-tractors; and in 2001 for trailers manufactured before 1993). Further, in 2012, the National Highway Traffic Safety Administration (NHTSA) proposed mandating electronic stability control for tractor-trailers and motorcoaches but not for single-unit trucks. Many studies of truck safety have examined fatalities as the sole outcome of interest. Tractor-trailers result in a larger proportion of fatal injuries from large truck crashes, which is one reason why some truck safety regulations have been limited to tractor-trailers and trailers. However, this study shows that there are substantial societal impacts resulting from non-fatal injuries arising from single-unit truck crashes. Emergency department visits, inpatient hospitalizations,3 and hospital costs4 that result from the crashes provide measures of the adverse effect of non-fatal injuries on the public. This study also shows that federal and state databases frequently misclassify single-unit trucks and thus undercount the total number of fatalities resulting from single-unit truck crashes by approximately 20 percent. The primary focus of this study was on the risks of single-unit truck crashes, and these risks were compared with those of tractor-trailer crashes. This study used a variety of data sources. Crash Outcome Data Evaluation System (CODES) data, which links hospital discharge records with police accident reports, were obtained from five participating states (Delaware, Maryland, Minnesota, Nebraska, and Utah) and served as the primary source of data for injury severity and hospitalizations in relation to truck and accident characteristics. Additional databases used include Trucks in Fatal Accidents (TIFA) and the Fatality Analysis Reporting System (FARS) (fatal crashes); the National Automotive Sampling System (NASS)/General Estimates System (GES) (national estimates of non-fatal injuries); and the Large Truck Crash Causation Study (LTCCS) (truck crash investigations with details not available from the other sources). To improve the quality and accuracy of CODES data, the NTSB developed and used a program to decode truck vehicle identification numbers (VIN); this program was used in conjunction with VIN-derived gross vehicle weight ratings (GVWR) supplied by NHTSA. Additionally, the CODES staff used statistical procedures to impute missing values for critical variables in the data sent to the NTSB and thereby maximize the data available for analysis. This approach avoids the bias introduced by omitting records with missing values. This comprehensive approach resulted in a detailed characterization of single-unit truck crash types and the associated fatalities and injuries.
TO THE NATIONAL HIGHWAY TRAFFIC SAFETY ADMINISTRATION: Develop performance standards for side underride protection systems for single-unit trucks with gross vehicle weight ratings over 10,000 pounds.
Original recommendation transmittal letter:
Open - Unacceptable Response
Washington, DC, United States
Addressee(s) and Addressee Status:
NHTSA (Open - Unacceptable Response)
Safety Recommendation History
We are disappointed that you have not updated us regarding your progress toward developing performance standards and requirements for either single-unit truck visibility enhancement or side underride protection systems. Please send us an update outlining your planned actions and a timeline for addressing this recommendation. Pending our receipt of that information, Safety Recommendations H 13-11 through -14 remain classified OPEN--UNACCEPTABLE RESPONSE.
We are disappointed by the lack of progress that you have made toward requiring a side underride protection system, and are concerned that you consider this issue a secondary priority. Prototype side underride systems are currently available in both the United States and Europe. Federal performance standards and a requirement for these systems would ensure a consistent approach toward their further development and application. Accordingly, pending your completion of the recommended actions, Safety Recommendations H-13-13 and -14 are classified OPEN—UNACCEPTABLE RESPONSE.
-From David J. Friedman, Deputy Administrator: Last year, NHTSA completed a two-year research program with the University of Michigan Transportation Research Institute (UMTRI) to collect and analyze crash data on rear underride in fatal truck crashes. The study was expanded to analyze the incidence of side underride crashes through a clinical review of cases in the Large Truck Crash Causation Survey (LTCCS). The UMTRI evaluation recorded light vehicle side underride of a cargo body or trailer in 52 of the 411 cases. However, the degree of override/underride was not specified in the analysis. Hence, the agency decided that a more detailed analysis was warranted and is in the process of examining these cases further. Upon completion, we will make a determination as to the need to regulate side underride guards, or whether further research is warranted. Factoring into this decision will be information about cost and weight. A recent SAE International paper, 2014-01-0565, estimated the weight of side underride guards for single unit trucks to be (653 pounds) and trailers (853 pounds). We note that the agency's efforts in this area are a secondary priority to upgrading Federal motor vehicle safety standards for rear impact guards. See 79 FR 39362.
According to Title 49 United States Code Section 1135, “the Secretary [of Transportation] shall give to the [NTSB] a formal written response to each recommendation not later than 90 days after receiving the recommendation.” Nearly a year has passed since we issued Safety Recommendations H-13-11 through -18, and we have not yet received your response regarding actions to address them. Accordingly, Safety Recommendations H-13-11 through -18, which have been classified “Open?Await Response” since their issuance, are now classified OPEN—UNACCEPTABLE RESPONSE.
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