Truck Underride Guards: Improved Data Collection, Inspections, and Research Needed

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.

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.

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.

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.

An “underride” crash occurs when a passenger vehicle slides under the  body of a tractor-trailer or “single-unit truck,” such as a delivery or dump  truck. Due to the height difference between the vehicles, the car’s safety  features are bypassed because the point of impact is not the front bumper  of the car. Without these safety features to absorb the force of the  collision, the passenger compartment can be crushed when it contacts  the truck, potentially resulting in death or severe head and neck injuries  for the occupants. To help prevent or mitigate these crashes, federal  regulations require that the rear end of the trailer have a guard meeting  specific crashworthiness standards. With these guards in place, the front  of the car will impact the guard instead of sliding under the trailer and the  car’s safety features will engage to offer some protection to the car’s  occupants. Rear guards of specific dimensions are also required for  single-unit trucks, but these guards are not required to be able to  withstand the force of a crash. There are no federal requirements for side  or front underride guards on any type of large truck in the United States.

However, legislation aimed at, among other things, requiring the use of  side and front underride guards on all large trucks was introduced in the  House of Representatives and the Senate in December 2017. New  legislation regarding underride crashes was introduced in March 2019.

You asked us to review data on truck underride crashes and information  related to rear, side, and front underride guards in the United States. This  report examines: (1) the data the Department of Transportation (DOT)  reports on truck underride crashes and (2) the development and use of  truck underride guard technologies in the United States.

To address both objectives, we conducted a literature review to identify  studies regarding truck safety, in general, and underride guards, in  particular; we reviewed these studies and other documentation collected  from interviewees, as described below. We also interviewed a variety of  stakeholders familiar with topics related to underride crashes and guards,  including: officials from DOT’s National Highway Traffic Safety  Administration (NHTSA), as well as NHTSA’s data validation and training  contractor; the Federal Motor Carrier Safety Administration (FMCSA); the  National Transportation Safety Board (NTSB) and representatives from  the Insurance Institute for Highway Safety (IIHS). We interviewed seven  trailer manufacturers, nine trucking industry organizations, four  organizations representing tractor-trailer fleets, nine traffic safety groups,  and four organizations involved in transportation research. Additionally,  we interviewed officials of five state DOTs, five state police departments,  as well as two local police departments. In selecting the states and  localities, we considered various factors—such as reported underride  crash fatalities and highway vehicle miles traveled—to identify states that  were similar in highway traffic trends and large truck-related fatality rates,  but that collected underride crash data differently. The results of these  interviews are not generalizable to all states and localities; however, they  offer examples of the types of experiences state DOTs and state and  local police have with underride crashes and inspections. We also  interviewed officials from transportation agencies in Canada and the  European Union.

For the first objective, we also analyzed DOT data on underride crashes  and fatalities from 2008 through 2017—the 10 most recent years for  which these data were available—and reviewed crash report forms from  all 50 states and the District of Columbia. We compared NHTSA’s data  collection efforts to federal internal control standards related to use of  quality information. For the second objective, we reviewed NHTSA’s and  FMCSA’s regulations requiring rear guards, FMCSA’s regulations on  commercial vehicle inspections, DOT’s documentation on underride  guard technologies, and DOT’s data on commercial vehicle inspections.  To assess the reliability of DOT’s data on underride crashes and fatalities  and commercial vehicle inspections, we reviewed relevant documentation  and spoke with agency officials about the data’s quality control  procedures. We determined that the data were sufficiently reliable for the  purposes of this report, specifically to provide a high-level overview of  underride crashes and fatalities, as well as commercial vehicle  inspections within recent years. However, we did identify potential  underreporting of underride crashes and fatalities, as discussed in this  report. We compared DOT’s efforts to pertinent agency regulations on  commercial vehicle inspections, federal internal control standards related  to use of quality information, and a statement of federal principles on  regulatory planning and review. See appendix I for a detailed description  of our objectives, scope, and methodology, including a list of  interviewees.

We conducted this performance audit from January 2018 to March 2019  in accordance with generally accepted government auditing standards.  Those standards require that we plan and perform the audit to obtain  sufficient, appropriate evidence to provide a reasonable basis for our  findings and conclusions based on our audit objectives. We believe that  the evidence obtained provides a reasonable basis for our findings and  conclusions based on our audit objectives.

An underride crash can occur during a collision between a passenger  vehicle and a large truck—a tractor-trailer or a single-unit truck, such as a  delivery or dump truck—if the height difference between the vehicles is  sufficient to allow the smaller vehicle to slide under the body of the truck.  The front and rear of passenger vehicles are designed to crumple in a  crash and absorb the main force of an impact, while sensors detect the  impact and activate safety features within the passenger compartment,  such as air bags and seatbelt pretensioners. However, the point of  impact in an underride crash could be the hood of the passenger vehicle  or—more severely—the windshield. Such impacts can result in  “passenger compartment intrusion” by the large truck into the passenger  area of the smaller vehicle. This intrusion can kill passengers or leave  them with severe head and neck injuries. Underride guards on large  trucks essentially lower the profile of the truck’s body to be more  compatible with that of a passenger vehicle. An underride guard designed  to withstand the force of a crash can prevent the car from sliding under  the truck and provide an effective point of impact that will activate the  car’s safety features to protect the car’s occupants. Figure 1 shows  images from a video depicting the difference in underride crashes with  and without passenger compartment intrusion on the rear of a tractor- trailer.

Rear and side underride guards limit a passenger vehicle’s ability to go  under those areas of a trailer in a crash (see fig. 2). Front guards— currently used on tractors in some other countries, such as European  Union countries—can reduce the likelihood that a truck would ride over a  passenger vehicle in a crash, a situation sometimes referred to as  “override”. In addition to saving lives and reducing serious injuries,  improving traffic safety—including reducing underride crashes—may  provide other benefits to society. Specifically, NHTSA has reported that  preventing such crashes may result in savings in police and crash  investigation resources and reduced property damage, among other  things. Federal requirements, in regulations issued by NHTSA and  FMCSA, exist for the installation of rear guards on most large trucks, but  there are no federal requirements for side or front guards.

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.”  As part of this mission, NHTSA  requires that rear guards be installed on most trailers. Federal regulations  requiring rear guards of specific dimensions date back to 1952, but the  most current regulations—which set force and energy absorption  standards, in addition to dimensional requirements—became effective in  1998. These crashworthy rear guards must be designed and tested to  protect occupants in a crash of up to 30 miles per hour.

In December 2015, NHTSA published a notice of proposed rulemaking  (NPRM) that proposed to align U.S. regulations with stronger Canadian  rear guard standards. The Canadian standard includes a stronger  energy absorption requirement: 20,000 joules—a measurement of  energy—as compared to 5,650 joules in the U.S. NHTSA has not taken  action on this NPRM since it was proposed in December 2015. Single- unit trucks that are more than 30 inches above the ground are required to  meet the dimensional specifications for rear guards set in 1952 but are  not required to meet any force or energy absorption standards. NHTSA  introduced an advance notice of proposed rulemaking (ANPRM) in July  2015 that considered requiring rear guards with strength and energy  absorption criteria for all newly built single-unit trucks. However, NHTSA  has since withdrawn the ANPRM, stating that—based on the comments  received as well as analysis of the petitions—the changes being  considered were not justified.

Although there are no federal requirements for crashworthy side  underride guards, some crashworthy side guards are being developed.  For example, one aftermarket manufacturer has developed a side  underride guard that was crash-tested by IIHS and successfully  prevented underride crashes in tests at 35 and 40 miles per hour. Similar  looking technologies—including aerodynamic side skirts and  pedestrian/cyclist side guards—are installed on some trailers and single- unit trucks, but they are not meant to mitigate underride crashes (see fig.  3).

FMCSA’s primary mission is “to reduce crashes, injuries, and fatalities  involving large trucks and buses,” and it does this, in part, through  developing safety regulations. These regulations include requirements for  rear guards for trailers consistent with Federal Motor Vehicle Safety  Standards and for single-unit trucks that are more than 30 inches above  the ground, as well as for multiple types of commercial vehicle  inspections that are performed by, for example, motor carriers and drivers  to ensure that commercial vehicles are safely operating. Table 1  describes the types of commercial vehicle inspections.

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 NHTSA’s Fatality Analysis Reporting  System (FARS). FARS is a census of all fatal traffic crashes in the U.S.  When a fatal crash occurs, a state or local police officer typically  completes a crash report form unique to each state. These forms can  include a variety of data fields, such as the time of the crash, weather  conditions, and the number of killed or injured persons. In the case of an  underride crash, officers may indicate an underride crash occurred in a  specific field for recording this crash type or in a narrative field. FARS  analysts—state employees who are trained by NHTSA’s data validation  and training contractor to code state crash data for input into FARS—in  each state receive and analyze the data in the crash report forms in order  to compile a record of the fatal crash. FARS analysts rely on the  information within the crash report form in order to enter accurate data.

To encourage greater uniformity of crash data, NHTSA, FMCSA, and  other agencies and associations cooperatively developed the Model  Minimum Uniform Crash Criteria (MMUCC) in 1998. The MMUCC  guideline, currently in the fifth edition, identifies a minimum set of motor  vehicle crash data elements and their definitions that states should  consider collecting, but are not required to collect. 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. According to NHTSA  officials, the next updated version of the MMUCC is expected to be  issued in 2022.

Underride Crash Fatalities Reported by NHTSA Data Are Relatively Low but Are Likely Undercounted

Although Reported Underride Crash Fatalities Represent a Small Percentage of Total Traffic Fatalities, Underride Crashes Present a Greater Risk of Fatalities or Serious Injuries

From 2008 through 2017, the annual number of fatalities resulting from  underride crashes involving one or more trucks reported in FARS ranged  between 189 and 253, resulting in an annual average of approximately  219 fatalities (see table 2). Comparatively, the FARS data show an  annual average of about 34,700 total traffic fatalities and approximately  4,000 fatalities involving large trucks over the same period. Therefore,  reported underride crash fatalities on average accounted for less than 1  percent of total traffic fatalities and 5.5 percent of all fatalities related to  large truck crashes during this time frame.

Although reported underride crash fatalities make up a small proportion of  total traffic fatalities, NHTSA officials told us that severe underride  crashes—involving passenger compartment intrusion—are more likely to  result in a fatality or serious injury than crashes in which the passenger  vehicle’s safety features engage and are able to protect the occupants.  Officials from four state DOTs we spoke to also stated that while  underride crashes are not common, the consequences—fatalities or  serious injuries, including head or neck injuries—are more likely to be  severe. An official from one state DOT noted that their agency did not  consider underride crashes to be a high priority issue. However, upon  further review of the state’s underride crash data, this official stated that  while underride crashes may occur infrequently, they present a higher risk  of fatality than the official had previously realized. An official in another  state told us they do not regularly review underride crash data but, upon  analysis of the data, found that underride crashes constituted a larger  percentage than they anticipated—16 percent—of all fatal large truck  crashes in the state in 2017.

NHTSA’s FARS data show that most of the reported underride crash  fatalities occurred when the crash impact was located at the rear or sides  of a trailer. From 2008 through 2017, approximately 45 percent (825 of  1836) of reported fatalities in underride crashes with a recorded point of  impact on the large truck occurred when the initial impact of the crash  was the rear of the trailer. About 32 percent (590 of 1836) of reported  underride crash fatalities were in crashes where the side of the trailer was  the point of initial impact. Approximately 21 percent (392 of 1836) of  reported underride crash fatalities were in crashes with the initial impact  at the front of the tractor. These 392 fatalities from crashes involving the  front of a tractor could be crashes in which the tractor impacted the rear  of a passenger vehicle but might also have occurred in a head-on  collision between the car and the tractor. The point of impact for underride  crash fatalities with passenger compartment intrusion—the most severe  form of underride—had similar distributions, with most reported fatalities  occurring when the initial point of impact was the rear or side of the  trailer.

State and local police officials we interviewed said that the underride  crash fatality cases they are familiar with occurred in high speed  scenarios, often exceeding 55 miles per hour. For example, officials  representing a state police department described scenarios in which  passenger vehicles traveling at high speeds rear-ended tractor-trailers  stopped on the highway’s shoulder or slowed for highway construction;  similar scenarios occurred when tractor trailers failed to slow for stopped  traffic and crashed into the rear of passenger vehicles. However, on  average, 62 percent of fatalities from underride crashes with passenger  compartment intrusion reported in 2008 through 2017 did not include a  reported speed. For example, for these fatalities in 2017, 72 percent had  speed coded in FARS as missing or not reported. A state and a local  police official told us that determining the speed of an underride crash can  be challenging due to the often severely damaged condition of the  passenger vehicle following an underride crash. Officials representing  state police said that they are better able to document whether or not  speeding was a factor in an underride crash, rather than an exact speed.

IIHS representatives also acknowledged the difficulty in documenting the  speed involved in an underride crash, and further stated that this difficulty  brings into question the accuracy of the speed data that are recorded in  FARS for underride crashes.

Variability in the Data Collection Process Likely Leads to Underreporting

Stakeholders we interviewed told us that underride crash fatalities are  likely underreported in FARS due to several factors, such as variability  across states in defining underride crashes, inconsistencies in state crash  reporting forms and documentation methods, and limited information  provided to state and local police on how to consistently identify and  record underride crash data. These factors could contribute to police  officers incorrectly and inconsistently documenting underride crash data  on the crash report form. As a result, FARS analysts may not have  sufficient information to properly categorize the crash as an underride,  ultimately affecting the number of underride crash fatalities identified in  FARS. 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.

Other researchers and organizations have also commented on the quality  of NHTSA’s underride crash data. For example, IIHS representatives told  us that they compared underride crash cases in FARS and in NHTSA’s  and FMCSA’s Large Truck Crash Causation Study—a study of large truck  crashes from 2001 through 2003—and identified some cases that  involved underride crashes but that were not categorized as such in  FARS. Consequently, IIHS representatives stated that they have used  more general rear impact crash data as a proxy for underride crashes due  to their finding that underreporting of underride crashes occurs in FARS.  Additionally, the University of Michigan’s Transportation Research  Institute reported that it can be difficult or impossible to identify underride  in available computerized crash data files, such as FARS.

Variability in Underride Crash Definition

State and local police officers do not use a standard definition of an  underride crash when collecting data at the scene of a crash. NHTSA  officials told us that the agency’s definition for an underride crash—”a  vehicle sliding under another vehicle during a crash”—is found in the  FARS coding and validation manual, a document primarily used by FARS  analysts and researchers. The FARS coding and validation manual  further distinguishes underride crashes as those with and without  passenger compartment intrusion. The MMUCC, which includes  definitions of various crash-related elements, does not include a definition  of an underride crash. Among officials from the five state police  departments we interviewed, underride crash definitions varied, even  within states. For example, in one state, an official from one local police  department said that a passenger vehicle would need to have over 50  percent of its hood underneath the trailer to constitute an underride crash,  while other officials within the state police used a broader definition  consistent with NHTSA’s definition, i.e., a vehicle going underneath  another vehicle by any amount. A state police official and a local police  official we interviewed indicated that they would like a clearer definition of  the conditions that constitute an underride crash to help them better  identify these crashes. Further, representatives from NHTSA’s data  validation and training contractor told us 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. A standard definition of an underride crash, for  example in the MMUCC, would provide greater assurance that underride  crashes are accurately recorded.

Inconsistency in State Crash Reporting Forms and Documentation of Underride Crashes

While all states have a crash report form to gather data following a crash,  these state forms vary in whether and how underride crash-related  information is collected. Specifically, for the most recent crash report  forms we examined from the 50 states and the District of Columbia, as of  October 2018:

17 state forms have a specific field for “Underride.” Eleven of these  forms also have data fields for passenger compartment intrusion.

32 state forms have a point of impact or area damaged field for  “undercarriage.” The point of impact field is generally intended to be  used to indicate the locations of initial impact or area that was  damaged for all vehicles involved in the crash. Some state police and  transportation officials we spoke with noted that this field could be  used to indicate that an underride crash occurred, as the initial point  of impact on a large truck could be the undercarriage in such a crash.

Two states, California and Hawaii, do not have a data element related  to underride crashes or undercarriage on their state crash report  forms.

The presence of an underride field in state crash report forms may affect  the extent to which underride crash fatalities are captured in FARS. For  example, we observed that after a state revised its form to remove the  underride field, the number of reported underride crash fatalities  significantly decreased, potentially indicating that underride crashes were  being underreported after the change. Conversely, in another state, we  observed that the number of reported underride crash fatalities  significantly increased following the addition of an underride field to the  crash report form, potentially indicating that underride crashes were being  reported more accurately following the change.

States have their own discretion to develop crash report forms based on  several factors that may be particular to each state. For example, states  include or exclude certain data elements on their crash report forms  based on the traffic safety priorities within that state. Officials we  interviewed from two state police departments told us that they do not  have an underride field on their crash report forms because underride  crashes are not a traffic safety priority for them. In another state, state  DOT officials told us that they chose to include an underride field on the  crash report form to better align with the FARS data fields, including those  fields related to underride. States may include certain data elements on  their crash report form based on the recommended data elements in the  MMUCC. However, while the MMUCC was developed to encourage  greater uniformity of crash data, its guidelines are voluntary, and it does  not currently include references to underride or override crash data  elements. In its June 15, 2017, report, the Post-Accident Report Advisory  Committee—a group appointed by the FMCSA Administrator to provide  input on additional data elements to be included in police accident reports  involving commercial motor vehicles—suggested that MMUCC data  elements be updated to include a collection of information about whether  underride and override are involved in a crash. However, according to the  MMUCC’s standard development process and NHTSA officials, to adopt  new data elements, the entire MMUCC expert panel—which is comprised  of stakeholders representing NHTSA, FMCSA, the Governors Highway  Safety Association, states, data collectors, data managers, data users,  and safety stakeholders—must reach at least 70 percent agreement for  approval of new changes to the MMUCC. Under the MMUCC’s standard  development process, the MMUCC expert panel will consider  recommendations and proposed changes to the MMUCC guidelines,  including those proposed by NHTSA in the months preceding the next  MMUCC update in 2022.

In states that do not include a specific underride crash field in the state  crash report form, state and local police officers we interviewed told us  that officers responding to a crash may describe underride crashes in the  diagram or narrative fields of the form. However, these officers said that a  police officer may inappropriately document an underride crash as a rear  impact crash. Similarly, officers may categorize the crash as both an  underride and an override crash, which NHTSA’s FARS coding and  validation manual indicates would be incorrect. Selected state officials  told us that unless the officer documenting the crash specifically  describes an underride crash in the narrative field, FARS analysts at the  state level who review the crash report forms will not have the information  to know if a crash involved underride.

Police officers we interviewed in states that include “undercarriage” rather  than a specific underride crash field in the crash report form told us that  they may use the option as a proxy for an underride crash; however, this  field may be used inconsistently. For example, in one state, state police  officers said they would select “undercarriage” on the crash report form to  reflect an underride crash, whereas a local police officer in the same state  said that local officers would not use that field to identify an underride  crash occurred and, instead, would document the underride crash in the  narrative. NHTSA’s data validation and training contractor told us that it is  not a recommended practice for officers to select “undercarriage” as a  proxy for underride crashes, noting that this inconsistency could lead to  inaccuracies in the resulting FARS data. Including underride as a  recommended data field in the MMUCC would provide greater assurance  that underride crashes are accurately recorded.

State and local police officials we interviewed said that they receive  limited or no training on how to identify and record information for  underride crashes. Officials from all five state police departments we  spoke with said that they develop their own crash reporting training for  police. This training emphasizes overall crash reporting with a limited  focus, if any, on underride crashes. An official representing one state  police office said that the state police provide training on how to complete  crash reports and general traffic safety, whereas FARS analysts—often  within the state DOT—are concerned with the quality of data collection for  data analysis purposes, which is not a primary focus of law enforcement  training. State and local police officials we interviewed said they generally  have limited to no follow-up or continuous training on crash reporting  beyond initial police academy training. Local police we interviewed also  told us that while they develop and implement their own crash report  training, they may also receive training from the state police. Some state  police officers that we spoke with said that they conduct training for local  police departments when requested. One local police official we spoke  with said that officers have limited exposure to underride crashes in these  training sessions and that the average officer would likely not know how  to appropriately identify an underride crash. Officials we spoke with from  three state and two local police departments stated that additional  information to police departments on underride crashes could help  improve data collection and overall traffic safety.

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. According to NHTSA’s data validation and training  contractor, the contractor trains FARS analysts on identifying underride  crashes. Specifically, the contractor trains FARS analysts to review the  crash report forms for sufficient detail to meet the definition of an  underride crash and determine if a crash involved underride for entry in  FARS. NHTSA officials told us that it is the responsibility of state police  academies to train law enforcement officers to conduct on-site  investigations and complete crash report forms. NHTSA officials said that  they do not currently 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, for example through  DOT’s Enforcement and Justice Services Division. NHTSA officials  acknowledged that it would be feasible to also 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.

Underride Guards Are in Varying Stages of Development, and Gaps Exist in Inspection and Research

Underride guards for the rear, side, and front of tractor-trailers and single- unit trucks are in varying stages of development. NHTSA has issued an  NPRM proposing to strengthen rear guard requirements for trailers, and  estimates that about 95 percent of all newly manufactured trailers already  meet the stronger requirements. While FMCSA requires commercial  vehicles to be inspected to ensure they are safe, rear guards may not be  regularly inspected. Side underride guards are being developed, but  stakeholders identified challenges to their use, such as the stress on  trailer frames due to the additional weight. NHTSA has not performed  research on the overall effectiveness and cost of these guards, and  manufacturers we interviewed told us that they are hesitant to invest in  developing side underride guards without such research. In response to 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. NTSB has further recommended that NHTSA develop  standards for crashworthy underride guards for single-unit trucks—such  as dump trucks—but NHTSA recently concluded that these standards  would not be cost effective.

Most Newly Built Trailers Are Equipped with Rear Guards That Exceed NHTSA Requirements

All seven of the eight largest trailer manufacturers—which are responsible  for about 80 percent of the trailers on the road in the U.S.—we spoke with  told us that they have been building to the stronger Canadian rear guard  standard since those requirements became effective in 2007. Some  manufacturers said that since trucking company operations may span the  border between Canada and the U.S., it was easier to build to a single  standard rather than manufacture trailers that comply with either the  Canadian requirements or the U.S. requirements. NHTSA is considering  strengthening the U.S. requirements for rear guards to align with the  Canadian rear guard standards. As part of the 2015 NPRM on  strengthening the U.S. requirements to the level of the Canadian  standards, NHTSA estimated that 93 percent of all newly manufactured  trailers in the U.S. are already equipped with a rear guard that meets the  Canadian standard. In July 2018, NHTSA officials told us that figure had  increased to 95 percent of all newly manufactured trailers, with the  remaining 5 percent from smaller manufacturers who may not wish to  incur the additional cost or weight of a Canadian-style rear guard.  Trucking industry stakeholders told us that the average lifecycle of a  trailer varies: one said the lifespan is 10 to 15 years and another stated a  12-year lifespan.

NHTSA performed a cost-benefit analysis as part of the 2015 NPRM in  which it preliminarily estimated that requiring newly manufactured trailers  to include rear guards built to the new standard would be cost-beneficial.  Specifically, NHTSA’s analysis found that the cost of a rear guard that  meets the Canadian standard was approximately $500 per trailer, which  was $229 more than a guard that complies with the existing U.S.  requirement. NHTSA’s analysis also found that a Canadian-style rear  guard was heavier than its U.S. counterpart. The rear guard NHTSA  studied that complies with current U.S. regulations weighed 172 pounds,  whereas those meeting the Canadian standard weighed between 191 and  307 pounds. Regarding benefits, NHTSA estimated in 2015 that— accounting for the trailers that already meet the stronger standard— adopting the Canadian standard would prevent about one fatality and  three serious injuries per year. According to DOT, these estimates may  have since changed, as a higher percentage of trailers are now  manufactured to meet the Canadian standards. Comments on this NPRM  varied. Some comments were in support of the measure, citing the safety  benefits. Other comments noted that automated driver assistance  technology may offer better outcomes. Further, some comments called  for NHTSA to take additional steps to improve the safety capabilities of  rear guards, such as allowing fewer exemptions from compliance. NHTSA  has not taken action on this NPRM since it was proposed in December  2015. NHTSA officials we interviewed could not provide information on  when the NPRM would move forward.

The largest trailer manufacturers have also taken steps to further improve  the design of rear guards to prevent underride crashes in a range of  scenarios. Because IIHS found that the weakest points for rear guards  are generally the outer edges furthest from the center of the guard, it  created a procedure to test the ability of rear guards to withstand crashes  at different overlap points, starting at the center of the guard and moving  closer to the endpoints. Specifically, this procedure involves three crash  tests using full width, 50-percent, and 30-percent overlap of the front of  the car with the rear guard, as depicted in figure 4. According to IIHS, as  of September 2018, all of the top eight trailer manufacturers operating in  the U.S. have successfully passed these tests. Some of these  manufacturers provide the improved rear guards as a standard feature on  all new trailers, while others offer them as an option for purchase.

In addition to strengthening rear guards on trailers, advancements in  automatic braking systems in passenger vehicles may help reduce the  frequency of underride crashes. These systems, though not federally- required, have been available and installed in some passenger vehicles  and tractors and are designed to detect objects or other vehicles in front  of the vehicle and automatically apply the brakes to avoid or lessen the  severity of an impact. According to NHTSA, twenty automakers  representing more than 99 percent of the U.S. automobile market have  agreed to make automatic braking systems a standard feature on newly- built passenger vehicles starting in 2022. These braking systems may  help reduce the number of passenger vehicles striking the rear of tractor- trailers, potentially reducing the frequency of underride-related crashes,  fatalities, and injuries.

Rear Guards in Use on Roads May Not Be Regularly Inspected

FMCSA regulations require commercial vehicles operating in interstate  commerce to be inspected to ensure they are safe. However, the rules do  not specifically include an inspection of the rear guard. After a rear guard  has been installed on a new trailer, stakeholders told us that the guard  may be damaged during normal use (see fig. 5), for example by backing  into loading docks. However, only certain roadside inspections—which  are performed at random or if an officer suspects a problem—specifically  require the rear guard to be inspected. Specifically, of the eight types of  roadside inspections, representatives of the Commercial Vehicle Safety  Alliance (CVSA)—which helps develop roadside inspection standards— told us that four require the rear guard to be inspected.

Stakeholders we interviewed told us that a trailer could go its entire  lifecycle—estimated as typically 10 to 15 years—without ever being  selected for a roadside inspection. FMCSA data show that although rear  guard violations may be identified during roadside inspections, they  constitute a small percentage of all violations. For example, out of about  5.8 million violations identified during roadside inspections in 2017,  approximately 2,400, or 0.042 percent, were rear guard violations. In an  effort to learn more about rear guard violations, CVSA encouraged  commercial vehicle inspectors to specifically focus on rear guards during  their roadside inspections performed from August 27 through 31, 2018.  According to these data, for the more than 10,000 trailers inspected  during that 5-day time frame, about 900 violations (about 28 percent of all  violations identified) for rear guard dimensional or structural requirements  were identified, including almost 500 instances where the rear guard was  cracked or broken, or missing altogether. A CVSA representative stated  there was a greater percentage of violations identified because inspectors  were asked to specifically focus on the rear guard during this effort.

Inspectors performing annual inspections—which can include employees  of the motor carrier—rely on a checklist established in FMCSA  regulations, known as “Appendix G.” This appendix specifies what  equipment must be inspected, such as the brake system, lighting, and  wheels. Appendix G does not list the rear guard as an item to be  inspected. In August 2018, CVSA petitioned FMCSA to amend  Appendix G to include rear guards as an item to be inspected. According  to CVSA, in September 2018, FMCSA provided acknowledgment of its  intent to review CVSA’s petition.

FMCSA’s regulations, including those regarding commercial vehicle  inspections, help the agency achieve its safety mission of reducing  crashes, injuries, and fatalities. Further, Standards for Internal Control in  the Federal Government notes that management should use quality  information to achieve the entity’s objectives. Prior to receiving CVSA’s  petition to amend Appendix G, FMCSA officials told us that not including  rear guards in Appendix G does not affect commercial vehicle safety, as  FMCSA regulations require all parts and accessories specified within the  regulations—which includes the rear guard—to be in safe and proper  operating condition at all times. According to DOT, the agency does not  believe that motor carriers are ignoring the application of these  regulations to rear guards. However, without explicitly including the  inspection of the rear guard in Appendix G, 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.

Side Underride Guards Are Being Developed, but Limited Information Exists to Assess Overall Effectiveness and Cost

While not currently required in the U.S., crashworthy side underride  guards are being developed which could entail both costs and benefits to  society. For example, there is currently one IIHS-crash-tested aftermarket  manufacturer of side underride guards in North America, which has sold  about 100 sets of side underride guards. According to the manufacturer,  the cost of the guards starts at about $2,500 per trailer, though the price  could decrease in the future as the manufacturing process becomes more  efficient and greater quantities are built and sold. These side underride  guards have been crash-tested by IIHS and successfully prevented  underride crashes in tests at 35 and 40 miles per hour. As a result, the  benefits of such guards might include a reduction in the number of  fatalities in underride crashes. The manufacturer estimated that more  widespread use of side underride guards would occur over the next 3 to 5  years. However, the manufacturer also said that more information on how  side underride guards might affect everyday operations is needed before  more widespread adoption by the industry. Additionally, some trailer  manufacturers told us that they are in the process of developing side  underride guards, but none are currently available for purchase. For  example, a representative from one trailer manufacturer developing its  own side underride guards estimated that it would be feasible to have  these guards designed, tested, and available for sale within the next 2  years. However, the representative said that the manufacturer is hesitant  to invest additional resources because of uncertainty about potential  future regulatory requirements. Specifically, the manufacturer does not  want to invest additional resources to develop a side underride guard that  might later have to be redesigned to meet federal requirements, if such  requirements were to be established and to differ from the manufacturer’s  design specifications.

Representatives from several trailer manufacturers, trucking industry  organizations, and police departments we spoke with cited challenges  with the use of side underride guards that would need to be addressed  prior to widespread adoption by the industry. Officials from Canada and  the European Union—which also do not require the use of side underride  guards that can withstand the force of a vehicle crash—noted similar  challenges.

Weight: According to the aftermarket side underride guard  manufacturer, the side underride guards currently available for sale  weigh between 575 to 800 pounds in total. Representatives from two  trucking industry organizations we spoke with stated that the  additional weight from side underride guards may require carriers to  put more trailers on the roads to ship goods in order to stay under  federal maximum weight restrictions (generally 80,000 pounds).  Federal regulations allow for certain exemptions in the federal weight  limits, such as for auxiliary batteries. Some stakeholders also stated  that the additional weight from side underride guards would increase  fuel costs (assuming all else remains the same) and could put stress  on the trailer’s frame, reducing its lifespan and potentially increasing  maintenance costs.

Road clearance: Some stakeholders we interviewed—including two  trucking industry organizations, a tractor-trailer fleet operator, and a  trailer manufacturer—stated that side underride guards limit a trailer’s  clearance from the ground, which could limit the geographic locations  that could be serviced by a trailer or—if the guards drag along the  ground—result in damage to the guards or even the trailer. Conditions  involving limited clearance could include traveling over raised railroad  crossings or navigating sloped loading docks. While aerodynamic side  skirts may also drag along the ground in similar conditions, they are  more flexible than side underride guards and less likely to damage the  trailer.

Effects on under-trailer equipment and access: Installation of a side  underride guard may limit access to or displace equipment currently  underneath a trailer, including spare tires, fuel tanks, and  aerodynamic side skirts. Additionally, the rear axles of some trailers  can be adjusted to evenly distribute the weight of the trailer’s cargo.  For example, trailer manufacturers told us that when the axle is  moved to the furthest rear position of the trailer, a fixed-length side  underride guard could leave a gap large enough for a car to still have  an underride crash. Further, some police officers we interviewed told  us that it could be challenging to perform roadside inspections of  trailers equipped with side underride guards because the guards  could limit access to the underside of the trailer.

Representatives from three trucking industry organizations we spoke with  indicated that crash avoidance technologies may be more effective than  underride guards at minimizing underride crashes, including side  underride crashes. However, while these technologies have the potential  to mitigate crashes, it is unlikely that they will be available on a more  widespread scale in a time frame soon enough to render underride  guards unnecessary. While automatic braking systems for passenger  vehicles are to become a standard feature on newly built vehicles starting  in 2022, IIHS representatives told us that these systems are less effective  at detecting and mitigating side crashes than rear or frontal crashes.  Specifically, the representatives stated that automatic braking systems  would not be effective in situations where the passenger vehicle impacts  the side of a trailer at an oblique angle rather than at a perpendicular  angle. According to stakeholders we interviewed, it will take a  considerable amount of time for the passenger fleet to adopt automated  vehicle technologies, with some stating that there will be a mix of  automated and non-automated technologies on the nation’s highways for  decades—longer than the 3 to 5 years estimated by the side underride  guard manufacturer for more widespread use of these guards.

NHTSA recently issued a study on the safety performance of certain  materials used for side underride guards. However, NHTSA has not  performed research on the overall effectiveness and costs associated  with or the design of side underride guards. 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. Additional  research on the effectiveness and cost associated with side underride  guards could better position NHTSA to determine whether these guards  should be required and, if so, appropriate standards for their  implementation. Such research may also help provide information to  address the challenges stakeholders cited with side underride guards.

Stakeholders Generally Agreed That North American Tractor Designs May Mitigate the Need for Front Guards for Underride or Override Purposes

In general, there are two types of tractors used in tractor-trailer  combinations: conventional tractors, wherein the tractor is lower to the  ground and the engine is in front of the cab where the driver sits, and  “cab-over” tractors, which are designed so the driver sits atop the engine  (see fig. 6). Conventional tractors are generally used in North America,  whereas cab-over tractors are used more frequently in the European  Union.

Since 2000, the European Union has required tractors to include front  guards to improve the protection of passengers in cars involved in head- on collisions with tractors. These guards are designed to lower the front  profile of a cab-over tractor to be more compatible with that of a  passenger vehicle to reduce the potential for underride or override, and to  help absorb the force of a collision.

Some conceptual designs for front guards on conventional tractors have  been proposed by researchers in the U.S., but there are no designs  available for purchase or installation as there are for side underride  guards. Some research organizations have developed computer models  of front guards, but these guards have not been produced for U.S. tractor  configurations. Representatives from three trucking associations we  spoke with stated that their members were not researching, producing, or  installing front guards. A government official from Canada—where the  conventional tractor design is also commonly used—said that they did not  know of any tractor manufacturers or truck fleets that use front guards.  Representatives from a tractor manufacturer that operates in both the  U.S. and the European Union told us that front guard designs currently  used in the European Union would not be compatible with conventional  tractors used in the U.S., stating that these guards would need to be  installed in the same space that the bumper, frame, and some  equipment—including crash avoidance technologies—already occupy.

The design of conventional tractors may mitigate the need for front  guards for underride or override purposes, as the lower bumpers and  frame make the height of conventional tractors more compatible with  passenger cars. A 2013 NHTSA study found that tractors with lower  bumper heights were less likely to be involved in an override crash than  those with higher bumper heights. Government officials from the  European Union told us that they did not see the need for conventional  tractors to have front guards, since the lower bumpers essentially function  as guards in frontal crashes. Officials from a state DOT, a state police  department, and a local police department all stated that they do not see  the need for front guards because the tractor is already so low to the  ground.

Further, state and local officials we spoke with noted that the front  underride crashes they have seen often occurred at higher speeds, such as when a truck fails to stop for congested traffic or in a head-on collision  at higher speeds. In these cases, the speed combined with the much  greater weight of the truck could cause the truck to override the car (in the  first scenario) or the car to underride the tractor (in a head-on collision).  According to these officials, the force of the crash at those speeds— regardless of whether there was underride or override—would very likely  be unsurvivable.

Additionally, automatic braking systems in tractors and passenger  vehicles may further mitigate the need for front guards for underride or  override purposes. These technologies—which, according to a tractor  manufacturer we interviewed, have been available and installed in some  tractors—can potentially stop a tractor from, for example, overriding a  passenger vehicle by automatically applying brakes in situations where a  potential rear-end collision is detected. Representatives from a tractor  manufacturer told us that about 70 to 80 percent of all newly  manufactured tractors it produced are equipped with these braking  systems and estimated that more than 50 percent of newly built tractors  sold by all manufacturers in the U.S. include these systems. Additionally,  front guard researchers we spoke with told us that some front underride  guard systems would be optimally effective when paired with automated  technologies, such as automatic braking systems.

While stakeholders generally agreed that North American tractor designs  may mitigate the need for front guards for underride or override purposes,  NTSB has called for greater use of front guards. Specifically, in 2010,  NTSB recommended that NHTSA, among other things, develop  performance standards for front guards and, after doing so, require all  newly manufactured trucks weighing more than 10,000 pounds to install  these front guards. NTSB issued these recommendations based on its  investigation of a June 2009 multi-car crash on an Oklahoma interstate, in  which the driver of a tractor trailer failed to slow down for traffic stopped  on the roadway. NTSB reported that the tractor-trailer’s high impact  speed and structural incompatibility with the passenger vehicles  contributed to the severity of the crash. As of December 2018, NHTSA  had not implemented NTSB’s recommendations. NHTSA reported to  NTSB in 2014 that it was in the process of conducting further examination  of crash data, but that efforts in developing standards for front guards are  a secondary priority to upgrading rear guard standards. NTSB stated that  NHTSA’s response was disappointing and that it continues to believe that  NHTSA actions are needed to implement this recommendation.  Additionally, NTSB recommended in 2015 that NHTSA develop  performance standards and protocols for assessing forward collision  avoidance systems in commercial vehicles, which could also help to stop  a tractor from overriding a passenger vehicle. According to NTSB,  although NHTSA has performed some research on this technology, NTSB  has deemed NHTSA’s responses as unacceptable. NHTSA officials told  us that the agency anticipates completing relevant research and testing in  2019 that would give the agency the information it needs to make  appropriate decisions on next steps related to these NTSB  recommendations.

The Wide Variety of Single-Unit Truck Configurations Creates Challenges for Implementing Crashworthy Underride Guards

FMCSA regulations require rear guards for certain single-unit trucks, such  as delivery or dump trucks, that are more than 30 inches above the  ground. However, according to representatives of the trucking industry we  interviewed as well as NTSB, the wide variety of single-unit trucks makes  it challenging to develop a one-size-fits-all requirement for underride  guards. Single-unit trucks can vary widely with respect to weight,  dimensions, and purpose and can include large pick-up trucks, fire trucks,  and dump trucks. The FMCSA regulations exempt certain single-unit  trucks—such as those already low to the ground—from the requirement  to have a rear guard if the vehicle is constructed and maintained such  that the body or other parts of the vehicle provide rear end protection  comparable to rear guards required for other single-unit trucks.

A trucking industry representative we spoke with said that his association  was not aware of any manufacturers currently designing or planning to  design crashworthy rear, side, or front underride guards for single-unit  trucks due to the variability of single-unit truck design. Some U.S. cities,  such as Boston, require pedestrian/cyclist side guards be installed on  municipally owned single-unit trucks, but these guards are not designed  to mitigate a passenger vehicle underride crash.

Research shows that crashes involving single-unit trucks occur less often  and are less likely to cause serious injuries and fatalities than those  involving tractor-trailers. For example, a 2013 NTSB study of crash data  from 2005 through 2009 found that single-unit truck crashes occurred less  often, resulted in fewer fatalities, and were less likely to cause serious  injuries than tractor-trailer crashes. NHTSA has also acknowledged that  single-unit trucks represent the majority of the registered heavy vehicle  fleet, but account for a lower percentage—27 percent—of rear end  fatalities.

To help address fatalities associated with underride crash fatalities  involving single-unit trucks, as part of its 2013 study, NTSB  recommended that NHTSA develop standards for crashworthy rear, side,  and front guards for single-unit trucks, as well as devote efforts to crash  avoidance technologies and include more variables in FARS to improve  data collection. NTSB also noted that, because of the variability in vehicle  design and cargo body styles, safety countermeasures for single-unit  trucks would need to be adapted for different truck types to address  technical challenges to their implementation.

NHTSA published an ANPRM in 2015 that considered requiring rear  guards with strength and energy absorption criteria for all newly built  single-unit trucks. However, NHTSA subsequently found that the costs of  this requirement outweighed the benefits. Comments on this ANPRM  varied. For example, the American Trucking Associations stated that it  believed NHTSA underestimated the costs associated with installing  crashworthy rear guards for single-unit trucks. In contrast, IIHS, in its  comments on the ANPRM, questioned NHTSA’s assumptions and stated  that the agency was undervaluing the benefits and overestimating the  costs. Specifically, IIHS noted that NHTSA overestimated the additional  weight of the rear guards, thereby overestimating the cost by about 35 to  40 percent. IIHS also stated that due to concerns with the underlying  data, NHTSA underestimated the number of crashes into the rear of  single-unit trucks with passenger compartment intrusion. NHTSA officials  told us that they disagreed with IIHS’s assessment and stated that the  data NHTSA used in the ANPRM were valid and appropriate. The  ANPRM also considered requiring single-unit trucks to install red and  white retroreflective tape meant to increase the visibility of these trucks,  especially in the dark. NHTSA found that this requirement would be cost- effective at preventing or mitigating crashes involving single-unit trucks.  However, NHTSA has since withdrawn the ANPRM, stating that—based  on the comments received as well as analysis of the petitions—the  changes being considered were not justified.

The likely underreporting of underride crashes and fatalities due to  variability in the data collection process limits NHTSA’s ability to  accurately determine the frequency of such crashes. An underride field in  MMUCC and additional information from NHTSA on how to identify and  record these crashes 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 this issue. While the stronger rear guards being voluntarily  implemented by the largest trailer manufacturers show promise in  mitigating the potentially devastating effects of rear underride crashes,  rear guards will only be effective if they are properly maintained and  replaced when damaged. The lack of specific requirements that rear  guards be inspected annually for defects or damage potentially affects the  safety of the traveling public and FMCSA’s ability to achieve its safety  mission. Finally, designs of crashworthy side underride guards show  promise at mitigating underride crashes, but manufacturers may be  reluctant to move forward with further development of these types of  guards without information from NHTSA on the effectiveness, cost, and  implementation standards for these devices. With additional research on  resolving the challenges associated with side underride guards, these  guards may be closer to being a feasible solution than automated driver  assistance technologies designed to prevent or mitigate side impacts that  could lead to an underride crash.

We are making the following four recommendations to DOT:  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)

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)

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)

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)

We provided a draft of this report to DOT for comment. In its written  comments, reproduced in appendix II, DOT stated that it concurred with  our recommendations. DOT also provided technical comments, which we  incorporated as appropriate.

As agreed with your offices, unless you publicly announce the contents of  this report earlier, we plan no further distribution until 30 days from the  report date. At that time, we will send copies to the appropriate  congressional committees, the Secretary of Transportation, and other  interested parties. In addition, the report will be available at no charge on  the GAO website at http://www.gao.gov.

If you or your staff have any questions about this report, please contact  me at (202) 512-2834 or flemings@gao.gov. Contact points for our  Offices of Congressional Relations and Public Affairs may be found on  the last page of this report. GAO staff who made key contributions to this  report are listed in appendix III.

Appendix I: Objectives, Scope, and Methodology

Our work for this report focused on truck underride crashes, and the U.S.  Department of Transportation’s (DOT) efforts related to this issue. In  particular, 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.

For both objectives, we conducted a literature review to identify studies  regarding truck safety, in general, and underride guards, in particular,  published from 1970 through 2018. We conducted a search for relevant  peer-reviewed articles, government reports, trade and industry articles,  and think tank publications. Key terms included various combinations of  “underride,” “crash,” “collision,” and “guard.” We included those studies  that were methodologically sound and covered underride crash data,  guard technologies, and benefits and costs relevant to our scope.  Additionally, we interviewed and analyzed the perspectives of  government officials from DOT, the National Highway Traffic Safety  Administration (NHTSA), the Federal Motor Carrier Safety Administration  (FMCSA), and the National Transportation Safety Board. We interviewed  officials from foreign transportation agencies—Canada and the European  Union—that were selected based on our review of literature identified  above and recommendations from preliminary interviewees. We also  interviewed a variety of relevant non-governmental organizations to gain  their perspectives on topics related to underride crashes and guards.  These organizations represent a variety of key players in their respective  fields on underride crash-related topics. We grouped these entities into  the following categories: (1) trailer manufacturers, (2) trucking industry  organizations, (3) tractor-trailer fleets and related organizations, (4) traffic  safety organizations, and (5) research organizations. We interviewed  seven of the top eight trailer manufacturers in the United States, as  identified by the Insurance Institute for Highway Safety. We requested an  interview with Stoughton Trailers, but they declined to participate. The  organizations we contacted as part of this work are listed at the end of  this section. We also interviewed NHTSA officials and conducted semi- structured interviews with officials in five selected states, including  officials in five state departments of transportation and five state and two  local police departments to understand and identify limitations, if any, in  how underride crash-related data are collected and analyzed. The results  of these interviews are not generalizable to all states and localities;  however, they offer examples of the types of experiences state DOTs and  police have with underride crashes and inspections. We selected states  based on several factors to identify states that were similar in highway  traffic trends and large truck-related fatality rates, but collected underride  crash data differently. Selection factors included highway vehicle miles  traveled per state, total underride crash fatalities by state in 2016 as  reported by NHTSA, and the presence of an underride crash data field on  each state’s crash report form. Based on these factors, we selected and  conducted interviews with state DOT and state police officials in  California, Illinois, Indiana, Pennsylvania, and Tennessee. We also  corresponded with officials from the Ohio DOT for clarification questions.  We interviewed local police departments in Chicago, Illinois and Terre  Haute, Indiana.

To identify the data DOT reports on truck underride crashes, we analyzed  existing DOT data on underride crashes and fatalities from 2008 through  2017, the 10 most recent years for which these data are available. We  reviewed DOT documentation for policies and procedures on data  collection and data reliability assessments for underride crash-related  data. NHTSA fatality data came from the Fatality Analysis Reporting  System (FARS). FARS is a census of all fatal traffic crashes in the United  States that provides uniformly coded, national data on police-reported  fatalities. We analyzed these data to determine the reported number of  fatalities involving underride crashes. To assess the reliability of the  FARS data, we reviewed relevant documentation and spoke with agency  officials about the data’s quality control procedures. We determined that  the data were sufficiently reliable for the purposes of this report,  specifically to provide a high-level overview of underride crash fatalities  within recent years. However, we did identify potential underreporting of  underride crashes and fatalities, as discussed in this report. We also  reviewed NHTSA’s annual Traffic Safety Facts reports—which use FARS  data—to determine the annual number of traffic and large truck crash  fatalities from 2008 to 2017, the 10 most recent years for which these  data are available. We reviewed state crash report forms from all 50  states and the District of Columbia to understand the variability of  underride crash-related data elements and how such variability could  affect DOT’s data collection and analysis efforts. We compared NHTSA’s  data collection efforts to federal internal control standards related to use  of quality information.

To describe the development and use of truck underride guard  technologies in the United States, we reviewed research and  documentation on underride guards. Primarily, we reviewed documents  relating to underride guards from NHTSA and FMCSA, as well as  information from traffic safety groups, trucking industry organizations,  research organizations, and selected foreign transportation agencies. We  reviewed NHTSA’s regulations requiring rear guards, FMCSA’s  regulations requiring commercial vehicle inspections, DOT’s  documentation on underride guard technologies, and DOT data on  commercial vehicle inspections. To assess the reliability of DOT’s  commercial vehicle inspection data, we reviewed relevant documentation  and spoke with agency officials about the data’s quality control  procedures. We determined that the data were sufficiently reliable for the  purposes of this report, specifically to provide a high-level overview of  commercial vehicle inspections within recent years. We compared DOT’s  efforts to pertinent agency regulations on commercial vehicle inspections,  federal internal control standards related to use of quality information, and  a statement of federal principles on regulatory planning and review. We  spoke with relevant non-governmental organizations to obtain their  perspectives on the perceived benefits and costs of rear, side, and front  underride guards, and the potential factors that may influence the benefits  and costs.

Appendix II: Comments from the Department of Transportation

Appendix III: GAO Contact and Staff Acknowledgments

Susan Fleming, (202) 512-2834 or flemings@gao.gov.

In addition to the contact named above, Sara Vermillion (Assistant  Director); Daniel Paepke (Analyst in Charge); Carl Barden; Jessica Du;  Mary Edgerton; Timothy Guinane; David Hooper; Gina Hoover; Madhav  Panwar; Joshua Parr; Malika Rice; Oliver Richard; Matthew Rosenberg;  Pamela Snedden; and Michelle Weathers made key contributions to this  report.

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.