USDOT Agency Opens Discussion of Side Underride Guards

The National Highway Traffic Safety Administration (NHTSA) has published an Advance Notice of Proposed Rulemaking (ANPRM) on whether side underride guards should be required on new trailers and semitrailers. These side underride guards are not the typical lightweight airflow deflectors (side skirts) seen on semitrailers in the U.S. as a fuel efficiency measure. In the Infrastructure Bill, Congress mandated that NHTSA research the possible regulatory requirement on trailer manufacturers.

In crashes when the side of the truck impacts the passenger compartment, the motorist fatalities and injuries can be particularly gruesome. NHTSA examined side underride guards from the sole U.S. manufacturer that can withstand a 40 mph impact from a passenger car into the side of a trailer without “passenger compartment intrusion” resulting.

Comments are due by June 20, 2023. Read the proposal here:

NHTSA concluded from its examination of fatal accident reports that the presence of side underride guards would prevent an average of 17.2 fatalities and 69 serious injuries each year, with safety benefits ranging from $129 million to $166 million. On the other hand, the cost of equipping new trailers and semitrailers with side underride guards, including a “lifetime fuel cost” in recognition of the added weight, would run between $970 million to $1.2 billion annually. As NHTSA states, “…the lifetime costs of equipping new trailers and semitrailers with side underride guards is six to eight times the corresponding estimated safety benefits.”

An ANPRM is used by a regulatory agency to test out a proposal or solicit ideas before it drafts its Notice of Proposed Rulemaking, which is the actual rulemaking proposal. Here, NHTSA has a great number of unknowns to consider, such as:

  • Would the cost of side underride guards change if the sole U.S. manufacturer faced competition?
  • What are the costs, not considered in NHTSA analysis, of any necessary strengthening of trailer beams, frame rails and floors to accommodate side underride guards?
  • Are there practical issues in trucking operations with side underride guards, such as scraping road surfaces at rail crossings or difficulties in intermodal operations and at ports and freight docks?

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