Viaduc de Martrou, Road bridge in Rochefort, France.

The Viaduc de Martrou is a road bridge that crosses the Charente River between Rochefort and Échillais. It allows vehicle traffic to flow continuously in both directions across the waterway.

Built between 1989 and 1991 for the SEMDAS under the direction of SETEC TPI, the viaduct was erected by a Bouygues/Quillery (Eiffage) consortium using three pairs of mobile formwork carriages. For a time three bridges stood in line over the Charente here; the 1967 lift bridge was demolished in 1991 once the viaduct opened. Tolls for vehicles not registered in Charente-Maritime ended on 1 January 2004.

The bridge carries the road linking Rochefort, to the north, with Échillais and the routes to Royan and Île d'Oléron, to the south; on the Rochefort side it also leads toward La Rochelle and Île de Ré. Until 1 January 2004 it was tolled for vehicles not registered in Charente-Maritime; once the toll was lifted, traffic more than doubled in two years, and queues between the viaduct and the exit of the road from La Rochelle are now almost daily.

The bridge carries traffic between Rochefort and Échillais and has been free for all vehicles since 1 January 2004. It is the route toward Royan and Île d'Oléron on the Échillais side, and toward La Rochelle and Île de Ré on the Rochefort side. Since it became free, traffic has more than doubled, and queues between the viaduct and the exit of the road from La Rochelle are almost daily.

The two piers standing in the Charente rest on eight piles each, 2 m in diameter and driven at a 15° angle from a floating platform to 33.5 m below the river. Their 11 m diameter, 2 m thick footings were set using prefabricated concrete shells, so they never touch the riverbed.