This realistic mega construction short shows the full engineering process, from early quarry road alignment and foundation work to rising bridge piers, elevated connector spans, retaining walls, full spiral descent, asphalt paving, and final road finishing. A spiral bridge, loop bridge, helix bridge, or pigtail bridge is a road bridge which loops over its own road, allowing the road to climb rapidly. This is useful in steep terrain, or where the approach road to a bridge would terminate too far from the bridge's end. Despite its name, the typical. Watch how a giant spiral bridge road is built step by step inside a massive open-pit quarry. more Watch how. The Future of Bridges Construction with Pacific Spiral StructureWith our cutting-edge spiral structure system, we provide developers and builders the tools they need to seize control and ensure future-proof construction practices. The reason for the design was simple – it had to be high enough for steam boats to pass under it while still exiting onto Main. The Lincoln Tunnel Helix, known commonly as The Helix or the Route 495 Helix, is an elevated spiral bridge freeway that carries New Jersey Route 495 to and from the Lincoln Tunnel in Weehawken, New Jersey.