Interstate H-3

Interstate H-3 is a highway on Oahu that stretches across concrete viaducts and through two major tunnels cutting into the Koolau Mountains. The route connects the windward and leeward sides of the island, crossing steep terrain that would otherwise require a long detour.

Construction began in the 1980s but faced prolonged delays due to environmental concerns and legal challenges. The road finally opened in 1997 after years of dispute.

During construction, archaeologists discovered and preserved multiple ancient Hawaiian sites, providing insights into traditional settlements and practices.

The highway is passable in both directions and offers the fastest route between the two sides of the island. Drivers should exercise caution during rain, as the tunnels and viaducts can become slippery.

The two tunnels were bored directly through the mountain using advanced engineering techniques to work around extreme geological conditions. Few highway tunnels anywhere required such complex drilling and blasting methods.

Location: Honolulu County

Inception: December 12, 1997

GPS coordinates: 21.38499,-157.78590

Latest update: December 6, 2025 21:30