overpasses

An overpass is a structure that allows one roadway, railway, or path to pass above another without intersection at grade. It is a type of bridge used to separate traffic streams and improve safety and efficiency at busy intersections, rail crossings, highways, or urban areas. Depending on context, “overpass” may be used interchangeably with “flyover” or “bridge,” though in some regions a distinct term is preferred.

An overpass typically comprises a deck carried by supports such as girders or slabs, with piers or abutments transferring loads to the ground. The deck is designed for the expected traffic, with expansion joints to accommodate movement, parapets or guardrails to prevent falls, and drainage to avoid water accumulation. In many designs, the structure is reinforced concrete or steel, though masonry arches and composite materials have been used historically. Pedestrian overpasses may include stairs, ramps, or elevators and are built to meet accessibility standards.

Construction and maintenance: Overpasses are built by casting decks in place or installing pre-cast segments, with foundations anchored in soil or rock. Regular inspections monitor structural integrity, corrosion, settlement, and drainage. Maintenance may involve resurfacing, replacement of joints, and barrier repair.

Environmental and safety considerations: Lighting, visibility, wind loads, and flood risk are considered; alignment and sight distance are planned to minimize collisions. Viaducts are long sequences of spans across valleys or urban areas and are related structures but serve a broader transport purpose.