The first overpass

The earliest known overpass was a railroad flyover built in 1843 by the London and Croydon Railway at Norwood Junction in London.

The first overpass in the modern sense was constructed to carry railway traffic over another railway line, specifically to allow atmospheric railway vehicles to cross the Brighton Main Line safely without interfering with other trains . This structure is considered the world's first railroad flyover and marked a significant advancement in traffic management and railway engineering. For road traffic, London also saw one of the earliest road overpasses with the Holborn Viaduct, built between 1863 and 1869. This overpass was designed to allow horse-drawn carriages to cross the River Fleet valley without descending into the valley, improving traffic flow in central London. The viaduct is a notable Victorian engineering achievement, featuring multiple levels, ornate ironwork, and pedestrian access . Earlier historical examples of overpasses existed in ancient Rome, where bridges were used to carry aqueducts over roads and valleys, but these were primarily for water transport rather than traffic separation . Pre-industrial traffic rarely required grade separation, as horse-drawn vehicles and pedestrians could share the same level without significant congestion . In summary, the first functional overpass for traffic separation was the 1843 railway flyover at Norwood Junction, while the first major road overpass in London was the Holborn Viaduct, completed in 1869. These early structures laid the foundation for modern overpass and flyover design, influencing both railway and road infrastructure worldwide.