Rectangular steel beams supported by posts provide higher containment for bridges with high traffic volumes. Which railing is this?

• A. Box beam guardrails
• B. Steel tube railings
• C. W-beam bridge railings
• D. Thrie beam railings

Answer: (A)

Rectangular box beam guardrails provide higher containment because the hollow rectangular cross-section offers greater stiffness and energy absorption during a crash. This shape resists bending and penetration more effectively than round tubes or the more open profiles of W-beam or thrie-beam systems, especially when supported by posts along a bridge. On bridges with high traffic volumes, you want a railing that can contain or redirect a vehicle without it overtopping or breaking through, and box beams are designed to deliver that performance. The other rail types are suitable for standard or moderate traffic but generally offer lower containment under high-speed or heavy-vehicle impacts.