Cost-benefit analysis of side underride guards for new semitrailers in the United States
DOI:
https://doi.org/10.59490/pss.2.2026.8512Keywords:
Aerodynamic side skirt, Cost-benefit analysis, Federal safety standard, Regulatory analysis, Semitrailer, Side underride guardAbstract
In the United States, the severe consequences of side underride crashes are well documented, yet no federal regulation requires side underride guards on semitrailers. Side underride guards can prevent vehicle underride and protect cyclists and pedestrians. This paper develops a decision support framework using a cost-benefit analysis to evaluate a potential federal requirement for side underride guards on new semitrailers. Annually, side underride crashes result in an estimated 300 fatalities and 400 serious injuries, costing society $7.4 billion. To estimate how side guards could reduce these losses, the analysis models paired full-fleet reductions of 50/50, 100/100, and 150/150 (fatalities and serious injuries), then scales impacts to one annual production cohort of 221,000 new semitrailers. Present value is calculated over the 13.2-year service life at a 2 percent discount rate using costs of $1,500, $2,500, and $4,500 per semitrailer, and includes fuel economy adjustments from weight and, where applicable, integration with aerodynamic skirts. Present value net benefits range from $0.137 billion to $2.8 billion. Scenarios that included fuel-saving skirts yielded additional savings of approximately 500 gallons per semitrailer annually (5.2 metric tons of CO2), adding $4.9 billion in fuel and $3.3 billion in CO2 benefits. Monte Carlo simulations for the $2,500 guard plus skirt configuration estimated mean present value net benefits of $0.58 billion ($0.39 to $0.77 billion) for the 50/50 case, $1.71 billion ($1.35 to $2.11 billion) for the 100/100 case, and $2.84 billion ($2.30 to $3.45 billion) for the 150/150 case. Modeled net benefits were positive in all iterations. Results indicate that a federal requirement for side underride guards on new semitrailers would produce positive economic and safety effects and meet conditions identified by NHTSA and industry for side underride guard rulemaking. The analysis can be applied in other jurisdictions using local crash, cost, and fleet data.
One sentence summary: This cost-benefit analysis evaluates a potential federal requirement for side
underride guards on new U.S. semitrailers, estimates positive safety and economic benefits, and
presents a framework that can be applied in other jurisdictions.
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