The frog is a component of special trackwork where one rail crosses another. Openings called flangeways in standard frogs let wheel flanges pass through. When a wheel passes through the flangeway at the frog point, contact between the wheel tread and frog wing rail creates high-impact forces, noise, and vibration. Low-impact frog designs can reduce these effects, but little public data exist on their effectiveness, longevity, or maintainability.
TCRP Research Report 260: Low-Impact Frog Design Primer and Research Roadmap serves as a guide for transit agencies in selecting appropriate frog designs for noise and vibration mitigation and in maintaining effective noise and vibration performance through proper maintenance practices. It also offers a research roadmap for the rail transit community to focus its efforts to foster, support, monitor, disseminate, and implement research on frog system design.
National Academies of Sciences, Engineering, and Medicine. 2026. Low-Impact Frog Design: Primer and Research Roadmap. Washington, DC: The National Academies Press.
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