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| National Route 46 | |
|---|---|
| Name | National Route 46 |
| Country | Japan |
| Type | National |
| Route | 46 |
| Length km | 121.9 |
| Established | 1963 |
| Direction a | West |
| Terminus a | Akita |
| Direction b | East |
| Terminus b | Morioka |
| Previous type | Route |
| Previous route | 45 |
| Next type | Route |
| Next route | 47 |
National Route 46 is a national highway that links Akita City on the Sea of Japan coast with Morioka in Iwate Prefecture on the Pacific side of northern Honshu. The corridor traverses the Ou Mountains, connects urban centers such as Noshiro, Odate, and Kazuno, and provides a cross-island arterial route with strategic links to Route 7, Route 4, and the Tohoku Expressway. It serves freight, passenger, and regional transit, and intersects major railways including the Ōu Main Line and the Hanawa Line.
The route begins in western Akita near the junction with Route 7 and proceeds northeast through Daisen, skirting the foothills of the Mount Chokai volcanic complex before entering the central highlands. It climbs into the Ou Mountains via the Kosaka Pass corridor, descending toward the basins containing Odate and Kazuno. East of Kazuno the highway parallels the Kitakami River headwaters and meets the Tazawako region, passing within driving distance of Lake Tazawa and Moritake. Approaching Morioka, the alignment follows valleys carved by tributaries of the Kitakami River, intersects Route 4 near Shiwa, and terminates in urban Morioka close to the Akita Shinkin Bank headquarters and the Iwate Prefectural Office precincts. The corridor’s geology includes andesitic bedrock, pyroclastic deposits, and alluvial plains, which shape gradients and necessitate numerous retaining structures and tunnels such as the Horinai Tunnel.
Pre-modern tracks along portions of the present corridor were used during the Edo period as feudal domain routes connecting the Satake clan domains in the Akita Domain with Morioka Domain lands held by the Nanbu clan. During the Meiji Restoration era modernization, sections were upgraded to link emerging administrative centers and resource extraction sites, including mines operated by Kosaka Mining Company and timber concessions supplying Mitsui. Postwar reconstruction and the 1963 designation formalized the route under national highway numbering, integrating improvements promoted by the MLIT and regional offices in Akita Prefecture and Iwate Prefecture. Significant episodes include the 1972 realignment to bypass narrow mountain bottlenecks, the 1990 tunnel projects addressing winter closures after heavy snows linked to atmospheric patterns associated with the Aleutian Low, and emergency repairs following the 1993 Hokkaido earthquake peripheral disruptions. Local councils including Akita City Council and Morioka City Council have periodically lobbied for capacity and safety upgrades.
Key interchanges and junctions along the route include the western terminus junction with Route 7 in Akita, the interchange with Route 105 near Odate, the connection to Route 103 serving Towada-Hachimantai National Park approaches, the intersection with Route 341 in the Kazuno area, the link to Route 4 east of Morioka, and feeder access to the Tohoku Expressway via prefectural roads that serve Kitakami and Hanamaki. Several at-grade intersections occur in towns such as Yokote and Semboku, while grade-separated interchanges concentrate near urban termini and industrial zones like the Akita Port freight areas.
Traffic composition includes freight trucks carrying timber, mineral concentrates from legacy mines, agricultural produce from Akita Prefecture rice paddies, and manufactured goods destined for Sendai and Tokyo. Commuter flows increase near Morioka and Akita metropolitan areas, with seasonal tourism surges tied to Lake Tazawa, the Akita Kanto Festival, and winter ski areas accessed via feeder roads to Appi Kogen. Average daily traffic varies widely: lower-volume mountain segments often record under 5,000 vehicles per day, while approaches to major urban nodes surpass 20,000. Safety statistics compiled by the NPA highlight winter snowfall-related incidents and curve-related collisions in narrow passes; mitigation measures include avalanche sheds and weather monitoring coordinated with the Japan Meteorological Agency.
Recent projects financed through national and prefectural budgets have included shoulder widening, pavement overlays using high-toughness asphalt, seismic retrofits for bridges engineered under Seismic Isolation Technology guidelines, and expansion of snow-mitigation infrastructure. MLIT and prefectural planning bodies proposed phased tunneling and bypass schemes to reduce travel time and improve resilience against heavy snowfall; proposals reference technologies used on the Kanetsu Tunnel and project delivery models piloted on the Meishin Expressway. Future plans emphasize intelligent transportation systems (ITS) integration for dynamic traffic management, cooperative measures with the Tohoku Shinkansen corridor to coordinate freight-dominant time windows, and environmental mitigation to protect headwater streams designated under prefectural conservation statutes.
The route plays a central role linking the cultural landscapes of northern Akita and southern Iwate, enabling access to festivals such as the Akita Kanto and heritage sites including the Shirakami-Sanchi fringe areas. Economically, it supports forestry clusters in Kazuno and Odate, facilitates shipments from industrial firms including regional branches of Toshiba and Hitachi suppliers, and underpins tourism economies drawing visitors to Nyuto Onsen and Morioka’s wanko soba cultural scene. The corridor has influenced settlement patterns, bolstered inter-prefectural trade with markets in Sendai and Akita Port, and remains a focus for policy instruments balancing regional revitalization initiatives promoted by the Cabinet Office (Japan) and local revitalization bureaus.
Category:Roads in Akita PrefectureCategory:Roads in Iwate Prefecture