The Hernani Viaduct, framed into the HSR Vitoria - San Sebastián - Frontera Francesa, has a total length of 1033.429 m.
The structure crosses the River Urumea, which width rounds the 30 m in present, in three places. For this reason, the first cross is materialized with 36 m of span, a length which is the span normally used for access bridges.
The second crossing, due to a fleet angle between the bridge and the river, needs 67 m of span for respect this area of Public Domain.
Finally, in the third crossing, the fleet angle and the increasing of the river's width result in a final bridge with 120 m of span. This circumstance and other conditionings lead us to a stayed bridge typology for the second and third crossing of the River Urumea.