Analyzing the FMCSA's Refusal to Amend Regulations on Side Underride Guards

The Federal Motor Carrier Safety Administration (FMCSA) plays a pivotal role in establishing regulations that govern the safety of commercial vehicles on U.S. roads. Among the many safety measures proposed, side underride guards have emerged as a critical focus of advocacy efforts aimed at preventing catastrophic injuries and fatalities in side-impact collisions involving large trucks. Despite extensive research and mounting evidence that underscores the potential effectiveness of these guards in mitigating harm, the FMCSA has notably refrained from amending existing regulations to mandate their installation.

This refusal raises significant questions about the agency's decision-making process, the influence of industry lobbying, and the broader implications for road safety. In this article, we will delve into the reasons behind the FMCSA's stance, examining the regulatory framework, stakeholder perspectives, and the ongoing debate surrounding the efficacy of side underride guards. By analyzing the agency's reluctance to adopt these crucial safety measures, we aim to shed light on the complexities of regulatory policies in the realm of commercial vehicle safety and the urgent need for improved protections for vulnerable road users.

FMCSA Rejects Call to Revise Underride Guard Study

The Federal Motor Carrier Safety Administration (FMCSA) has declined a request to amend a federally funded study that the Insurance Institute for Highway Safety (IIHS) claims downplays the benefits of side underride guards on truck trailers. The dispute centers on the FMCSA’s exclusion of a cost-benefit analysis in its review of the technology—an omission that IIHS argues compromises the integrity of its advocacy efforts and the effectiveness of its safety awards.

In its formal correction request submitted in December, IIHS asserted that leaving out this key analysis undermines its credibility as an independent, data-driven authority in highway safety. The organization has long championed stronger underride protections, establishing the "Toughguard" award to incentivize manufacturers to exceed minimum federal standards for rear underride guards. IIHS now indicates that it is considering a similar award for side underride guards, based on its internal crash test data and evaluations of real-world accident outcomes.

The omission of the cost-benefit analysis, IIHS contends, damages its efforts to promote life-saving technologies. The organization fears that this could mislead stakeholders into thinking side guards are unjustified or unnecessary—potentially deterring manufacturers from further development of these protective features.

FMCSA Maintains Its Position on Data Standards

Despite these concerns, FMCSA stood firm in its response. In a letter released on Thursday, the agency said IIHS failed to meet the federal standards required to warrant a correction under the Information Quality Act. According to FMCSA, the burden lies with IIHS to prove that the original review lacked accuracy or objectivity. After reviewing the request, the agency concluded that no such failure occurred, and therefore no changes are needed.

FMCSA's defense rests on both methodological and practical concerns with the omitted cost-benefit study, which originated from the Volpe National Transportation Systems Center under the U.S. Department of Transportation. The agency highlighted what it sees as fundamental flaws in the report’s assumptions, data sources, and conclusions.

According to FMCSA, the Volpe study overestimated the number of potential crash scenarios in which side guards could offer protection. It also assumed higher-than-warranted effectiveness rates for the guards, even in situations where they wouldn't realistically apply—such as frontal collisions with pedestrians or cyclists. Additionally, the analysis failed to sufficiently account for the cost of implementation, including installation, ongoing maintenance, and increased fuel use from the added weight.

Setback for Side Guard Advocates

This ruling represents the second major setback in recent weeks for groups pushing for greater use of side underride guards. In March, the National Highway Traffic Safety Administration (NHTSA) rejected a related petition from the Institute for Safer Trucking, which called for an investigation into the recall of truck trailers lacking side guards. NHTSA concluded that the issues raised were better addressed through an ongoing rulemaking process related to underride protections, rather than through a formal investigation or recall process.

The FMCSA further justified its decision by pointing out that the Volpe report included data from crashes in which the victims were struck at points of the vehicle where lateral protection devices (LPDs) would have no practical effect—such as the front end of a commercial truck. These inclusions, the agency argued, skewed the data by inflating the number of crashes that could potentially be prevented by LPDs.

Because of this flawed methodology, FMCSA maintained that the report significantly overstated the benefits while minimizing the true costs of side underride guard implementation. For that reason, the agency concluded that the exclusion of the Volpe data from its review was both justified and necessary.

Conclusion: Ongoing Debate Reflects Broader Safety Concerns

The FMCSA’s decision not to revise its study underscores the ongoing tension between federal regulators and road safety advocacy organizations. While FMCSA argues it must rely on rigorous, standardized data to inform policy, groups like IIHS contend that dismissing certain analyses sets back critical safety advancements.

As the debate continues, it’s clear that side underride guard regulations remain a contested issue, with implications for public safety, industry costs, and policy transparency. Whether future rulemakings by NHTSA or FMCSA will address these concerns more fully remains to be seen—but the recent rejections suggest that advocates for side underride protection will need to continue building their case with even more robust and narrowly focused evidence.

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