Truck Underride Guards: Improved Data Collection, Inspections, and Research Needed
Fast Facts
A truck underride crash occurs when a car slides under a large truck, like a tractor-trailer. The car's passenger compartment can be crushed, potentially killing or severely injuring occupants. Researchers told us that underride crashes likely happen more often than the Department of Transportation's data suggests.
DOT requires trailers to have a rear safety bar—known as an underride guard—to prevent underride crashes, but it doesn’t require them to be inspected. DOT also hasn’t researched challenges to using underride guards on the sides of trucks.
We made 4 recommendations, including that DOT improve data and research the use of side guards.
In a simulated truck underride crash, a sedan slides under the back of a tractor-trailer.
The passenger compartment of a silver test sedan is crushed beneath the back of a tractor-trailer in a simulated crash.
Highlights
What GAO Found
According to crash data collected by police and reported by the Department of Transportation's (DOT) National Highway Traffic Safety Administration (NHTSA), fatalities from “underride” crashes, such as those pictured below, represent a small percentage of all traffic fatalities.
Crash Tests of Rear Guards with (left) and without (right) Passenger Compartment Intrusion
From 2008 through 2017, an average of about 219 fatalities from underride crashes involving large trucks were reported annually, representing less than 1 percent of total traffic fatalities over that time frame. However, these fatalities are likely underreported due to variability in state and local data collection. For example, police officers responding to a crash do not use a standard definition of an underride crash and states' crash report forms vary, with some not including a field for collecting underride data. Further, police officers receive limited information on how to identify and record underride crashes. As a result, NHTSA may not have accurate data to support efforts to reduce traffic fatalities.
Underride guards are in varying stages of development, and gaps exist in inspection of rear guards in current use and in research efforts for side guards.
NHTSA has proposed strengthening rear guard requirements for trailers (the rear unit of a tractor-trailer) and estimates about 95 percent of all newly manufactured trailers already meet the stronger requirements. Although tractor-trailers are inspected, Federal Motor Carrier Safety Administration annual inspection regulations do not require the rear guard to be inspected, so damaged guards that could fail in a crash may be on the roadways.
Side underride guards are being developed, but stakeholders GAO interviewed identified challenges to their use, such as the stress on trailer frames due to the additional weight. NHTSA has not determined the effectiveness and cost of these guards, but manufacturers told GAO they are unlikely to move forward with development without such research.
Based on a 2009 crash investigation, the National Transportation Safety Board (NTSB) recommended that NHTSA require front guards on tractors. NHTSA officials stated that the agency plans to complete research to respond to this recommendation in 2019. However, stakeholders generally stated that the bumper and lower frame of tractors typically used in the U.S. may mitigate the need for front guards for underride purposes.
Regarding single-unit trucks, such as dump trucks, NTSB has recommended that NHTSA develop standards for underride guards for these trucks, but the agency has concluded these standards would not be cost-effective.
Why GAO Did This Study
Truck underride crashes are collisions in which a car slides under the body of a truck—such as a tractor-trailer or single-unit truck—due to the height difference between the vehicles. During these crashes, the trailer or truck may intrude into the passenger compartment, leading to severe injuries or fatalities. Current federal regulations require trailers to have rear guards that can withstand the force of a crash, whereas the rear guards required for single-unit trucks do not have to be designed to withstand a crash. There are no federal side or front underride guard requirements.
GAO was asked to review data on truck underride crashes and information on underride guards. This report examines (1) the data DOT reports on underride crashes and (2) the development and use of underride guard technologies in the U.S. GAO analyzed DOT's underride crash data for 2008 through 2017; reviewed NHTSA's proposed regulations and research on new guard technologies; and interviewed stakeholders, including DOT officials, industry and safety groups, and state officials selected based on reported underride crash fatalities and other factors.
Recommendations
GAO recommends that DOT take steps to provide a standardized definition of underride crashes and data fields, share information with police departments on identifying underride crashes, establish annual inspection requirements for rear guards, and conduct additional research on side underride guards. DOT concurred with GAO's recommendations.
Recommendations for Executive Action
| Agency Affected | Recommendation | Status |
|---|---|---|
| Department of Transportation | The Administrator of the National Highway Traffic Safety Administration should recommend to the expert panel of the Model Minimum Uniform Crash Criteria to update the Criteria to provide a standardized definition of underride crashes and to include underride as a recommended data field. (Recommendation 1) |
Truck underride crashes are collisions in which a car slides under the body of a truck--such as a tractor-trailer or single-unit truck--due to the height difference between the vehicles. During these crashes, the trailer or truck may intrude into the passenger compartment, leading to severe injuries or fatalities. For fatal crashes, including fatal underride crashes, data are collected by law enforcement officials at the location of the crash, aggregated at the state level, and then transferred to the National Highway Traffic Safety Administration's (NHTSA) Fatality Analysis Reporting System (FARS). FARS is a census of all fatal traffic crashes in the U.S. In March 2019, GAO reported that from 2008 through 2017, an average of about 219 fatalities from underride crashes involving large trucks were reported annually, representing less than 1 percent of total traffic fatalities over that time frame. However, these fatalities were likely underreported due to variability in state and local data collection. GAO reported that state and local police officers do not use a standard definition of an underride crash when collecting data at the scene of a crash. Further, not all states include an underride field in state crash report forms that are completed following a crash. To encourage greater uniformity of crash data, NHTSA and other agencies and associations cooperatively developed the Model Minimum Uniform Crash Criteria (MMUCC) in 1998. However, the MMUCC, which includes definitions of various crash-related elements, does not include a definition of an underride crash, nor does it recommend underride as a data field. The MMUCC is updated about every 4 to 5 years. Prior to publication of each edition, an expert panel from the relevant agencies and associations convenes to review all proposed changes suggested by traffic safety stakeholders to determine what will be included in the MMUCC. GAO reported that representatives from NHTSA's data validation and training contractor stated that when they have identified anomalous patterns in underride crash data in FARS, the main reason for these anomalies has been varying definitions of this crash type, as reporting officers have many interpretations of what constitutes an underride crash. Standards for Internal Control in the Federal Government notes that management should use quality information to achieve the entity's objectives. Underreporting of underride crashes would affect the quality of NHTSA's data, thereby affecting the agency's ability to accurately identify the magnitude of underride-related crashes and limiting its ability to make informed decisions on rulemaking or other efforts that would help the agency meet its mission to improve traffic safety. As a result, GAO recommended that the Administrator of NHTSA should recommend to the expert panel of the MMUCC to update the Criteria to provide a standardized definition of underride crashes and to include underride as a recommended data field. On February 2, 2023, NHTSA published a notice in the Federal Register stating that it was revising the MMUCC and requesting comments on the draft MMUCC to inform appropriate improvements and identify stakeholder concerns. The draft MMUCC includes a definition of underride and includes underride as a recommended data field to be collected. According to Department of Transportation officials, NHTSA recommended to the expert panel of the MMUCC that this information be included in the updated MMUCC. As of May 2023, NHTSA anticipates that the newest version of the MMUCC will be published in early 2024. Including an underride field in the MMUCC would provide greater assurance that state and local police officers are accurately reporting data on underride crashes. Such reporting would, in turn, enable NHTSA to better identify and support measures-such as rulemakings and research efforts-to help address underreporting of underride crashes and fatalities.
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| Department of Transportation | The Administrator of the National Highway Traffic Safety Administration should provide information to state and local police departments on how to identify and record underride crashes. (Recommendation 2) |
Truck underride crashes are collisions in which a car slides under the body of a truck-such as a tractor-trailer or single-unit truck-due to the height difference between the vehicles. During these crashes, the trailer or truck may intrude into the passenger compartment, leading to severe injuries or fatalities. For fatal crashes, including fatal underride crashes, data are collected by law enforcement officials at the location of the crash, aggregated at the state level, and then transferred to the NHTSA Fatality Analysis Reporting System (FARS). FARS is a census of all fatal traffic crashes in the U.S. In March 2019, GAO reported that from 2008 through 2017, an average of about 219 fatalities from underride crashes involving large trucks were reported annually, representing less than 1 percent of total traffic fatalities over that time frame. However, these fatalities were likely underreported due to variability in state and local data collection. State and local police officials GAO interviewed said that they receive limited or no training on how to identify and record information for underride crashes. Some officials said that they develop their own crash reporting training for police, which emphasizes overall crash reporting with a limited focus, if any, on underride crashes. NHTSA provides training to FARS analysts on reviewing crash report forms and appropriately inputting data in FARS, but does not provide information on crash data collection to state and local police who initially collect the data. NHTSA officials said that they do not provide underride identification information directly to state and local police who initially collect the crash data. However, NHTSA does provide information to state and local police on other topics, such as improving traffic safety and driver behavior. At the time of GAO's report, NHTSA officials acknowledged that it would be feasible to provide information on identifying and recording underride crashes . Standards for Internal Control in the Federal Government notes that management communicates quality information externally through reporting lines so that external parties can help the entity achieve its objectives and address related risks . By providing information to state and local police departments-such as materials or instruction on the definition of an underride crash and how to appropriately document these crashes-NHTSA could improve the quality and completeness of underride crash data that police collect. As a result, GAO recommended that the Administrator of NHTSA should provide information to state and local police departments on how to identify and record underride crashes. On August 2, 2022, NHTSA-along with the Federal Motor Carrier Safety Administration-published an informational pamphlet to educate state and local police officers on how to identify and record underride crashes. Among other things, the pamphlet defines underride crashes and provides information to law enforcement on recording underride crashes. According to DOT, the informational pamphlet was posted on NHTSA's website on August 2, 2022 and will be further distributed to the law enforcement community through established partnerships, publications and a national law enforcement liaison network. This action will help provide greater assurance that state and local police officers are accurate reporting data on underride crashes. Such reporting can, in turn, enable NHTSA to better identify and support measures-such as rulemakings and research efforts-to help address underride crashes.
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| Department of Transportation | The Administrator of the Federal Motor Carrier Safety Administration should revise Appendix G of the agency's regulations to require that rear guards are inspected during commercial vehicle annual inspections. (Recommendation 3) |
Truck underride crashes are collisions in which a car slides under the body of a truck-such as a tractor-trailer or single-unit truck-due to the height difference between the vehicles. During these crashes, the trailer or truck may intrude into the passenger compartment, leading to severe injuries or fatalities. Federal regulations require trailers to have rear guards that can withstand the force of a crash. Federal Motor Carrier Safety Administration (FMCSA) regulations require commercial motor vehicles operating in interstate commerce to be inspected to ensure they are safe. However, in March 2019, GAO reported that FMCSA's rules do not specifically include an inspection of the rear guard. Only certain roadside inspections-which are performed at random or if an officer suspects a problem-specifically require the rear guard to be inspected. Stakeholders GAO interviewed indicated that a trailer could go its entire lifecycle-estimated as typically 10 to 15 years-without ever being selected for a roadside inspection. Further, inspectors performing annual inspections rely on a checklist established in FMCSA regulations that specifies what equipment must be inspected, such as the brake system, lighting, and wheels. This list does not include the rear guard as an item to be inspected, so there is no assurance that rear guards in operation will be inspected at least annually to ensure they perform as designed to prevent or mitigate an underride crash. This omission potentially affects FMCSA's safety mission to help ensure the safe operation of tractor-trailers on the nation's highways. Therefore, GAO recommended that the Administrator of FMCSA should revise the agency's regulations to require that rear guards are inspected during commercial vehicle annual inspections. Effective December 9, 2021, FMCSA amended the Federal Motor Carrier Safety Regulations to include rear impact guards on the list of items that must be examined as part of the required annual inspection for each commercial motor vehicle. This action will help ensure that rear guards on trailers perform as designed to protect car occupants from injury or death in the event of a rear underride crash.
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| Department of Transportation | The Administrator of the National Highway Traffic Safety Administration should conduct additional research on side underride guards to better understand the overall effectiveness and cost associated with these guards and, if warranted, develop standards for their implementation. (Recommendation 4) |
Truck underride crashes are collisions in which a car slides under the body of a truck-such as a tractor-trailer or single-unit truck-due to the height difference between the vehicles. During these crashes, the trailer or truck may intrude into the passenger compartment, leading to severe injuries or fatalities. In March 2019, GAO reported that side underride guards for trailers were being developed, but stakeholders GAO interviewed identified challenges to their use, such as the stress on trailer frames due to the additional weight. GAO also reported that while NHTSA had issued a study on the safety performance of certain materials used for side underride guards, it had not performed research on the overall effectiveness and costs associated with or the design of side underride guards. Further, representatives of trailer manufacturers stated that they were unlikely to move forward with developing side underride guards without such research. NHTSA's mission is to "save lives, prevent injuries and reduce economic costs due to road traffic crashes, through education, research, safety standards and enforcement activity." Additionally, a statement of federal principles on regulatory planning and review indicates that in deciding whether and how to regulate, agencies should assess all costs and benefits of available alternatives, including the alternative of not regulating, and that the agency should base its decisions on the best reasonably obtainable scientific, technical, economic, and other information. As a result, GAO recommended that the Administrator of NHTSA should conduct additional research on side underride guards to better understand the overall effectiveness and cost associated with these guards and, if warranted, develop standards for their implementation. In April 2023, NHTSA published a report titled "Side Impact Guards for Combination Truck-Trailers: Cost-Benefit Analysis." The report presents NHTSA's research on the effectiveness (e.g., mitigating fatalities and serious injuries) and costs (e.g., installation costs, fuel consumption) associated with equipping trucks with side underride guards. On April 21, 2023, NHTSA published an advance notice of proposed rulemaking (ANPRM) on side underride guards. The ANPRM seeks public comments on designs of side underride guards to reduce deaths and serious injuries resulting from underride crashes into the sides of trailers. By performing research aimed to better understand the benefits, challenges, and costs associated with side underride guards and seeking additional information on their design, NHTSA will be better positioned to determine whether these guards should be required and, if so, develop appropriate standards to implement such a requirement.
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