Zao-bashi, Road bridge in Nagaoka, Japan

Zao-bashi is a modern steel and concrete structure that spans approximately 800 meters across the Shinano River. It connects the eastern and western sections of Nagaoka and carries two major national routes that serve local and regional traffic.

Ferries crossed the Shinano River here until a motorized service began around 1921. The prefectural assembly approved a bridge in 1928, piers were finished in 1929, and a truss span opened in 1936 with wooden ramps. Floods repeatedly damaged the wooden parts, replaced in concrete in 1952 and 1957. The first bridge, 815 m long, was completed in 1958; the current 808 m bridge opened in 1994.

The bridge is named after Zao village, a former shogunate territory next to Nagaoka that was home to Zao-do Castle, a rare flatland castle predating Nagaoka Castle. Before the bridge, the Zao-Makiyama crossing was served by ferry; motorized ferries ran from around 1921 and became free once the route was taken over as a prefectural road.

The bridge is accessible to both pedestrians and vehicles, accommodating different types of traffic. Crossing during daylight hours is advisable when visibility is best and traffic patterns are more predictable.

The current bridge was built while the old Zao Bridge remained in use, so it curves at both ends to meet the existing roads. Downstream stands the Hokuriku Expressway's Shinanogawa Bridge; upstream is the Nagaoka Bridge of National Route 8's bypass.