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State Route 70 (SR 70) is a state highway in the U.S. state of California. Connecting Sacramento with U.S. Route 395 (US 395) near Beckwourth Pass (lowest in the Sierra Nevada) via the Feather River Canyon. Through the Feather River Canyon, from SR 149 to US 395, SR 70 is the Feather River Scenic Byway, a Forest Service Byway that parallels the ex-Western Pacific Railroad's Feather River Route. The Beckwourth Trail was the earliest predecessor of SR 70, which was a spur of the California Trail. This was followed by the railroad, mostly built on the route of the trail; a dirt road was needed for construction that was later converted into part of the present state highway. Construction on the highway began in 1928, which involved the boring of three tunnels. Previously, the road was signed as U.S. Route 40 Alternate, crossing the Sierra Nevada at a lower elevation than Donner Pass on US 40, now Interstate 80 (I-80). The road was renumbered SR 70 in the 1964 state highway renumbering. Today, portions of SR 70 have been upgraded to a four-lane expressway, and even a freeway in a few locations. ==Route description== State Route 70 begins at a partial interchange with SR 99 north of Sacramento, close to the Feather River Route rail line that parallels the entire highway, and heads north along a four-lane mix of expressway and freeway. Just north of the Bear River crossing / Yuba County line, in Plumas Lake, SR 70 becomes a freeway for the second time, which continues to just beyond the Yuba River in Marysville. Within that city, SR 70 makes two turns and overlaps SR 20 before heading north on a two-lane road. Another four-lane freeway begins south of SR 162 in Oroville, and ends at SR 149. SR 149 is a major connection northwest to SR 99, and became the straight-through movement when the construction to replace the intersection with an interchange was completed in November 2008. The State Scenic Highway portion of SR 70 begins at SR 149, which is where SR 70 turns northeast out of the Sacramento Valley and into the mountains. The short SR 191 spurs north to Paradise, while SR 70 crosses the West Branch Feather River on the double-decker West Branch Bridge, with the Feather River Route below. A short four-lane section runs over the bridge towards Jarbo Gap, where the present SR 70 merges with the old road (Dark Canyon Road) that was used before the Feather River was dammed to create Lake Oroville in the 1960s.〔Google Maps street maps and USGS topographic maps, accessed December 2007 via (ACME Mapper )〕 After crossing through Jarbo Gap, SR 70 drops down into the canyon of the North Fork Feather River, which it follows almost to Quincy, usually on the opposite side from the Feather River Route; this results in two places where both transportation lines cross the river and each other. The first of these is the Pulga Bridge, an arch bridge that crosses over a lower railroad truss bridge; soon after are the highway's three tunnels through rock formations in the canyon. After a fair distance through the canyon, and that formed by the East Branch North Fork Feather River, SR 70 reaches the junction with State Route 89 near Paxton; Routes 70 and 89 overlap southeast from that point, where the East Branch splits into Indian Creek and Spanish Creek.〔 The highway heads southeast, partly along the latter creek, past Keddie to Quincy in the American Valley. It leaves the valley via Greenhorn Creek, passing the Feather River Route's Williams Loop and then following the small Estray Creek to Lee Summit, which the rail line passes under in the Spring Garden Tunnel. This brings SR 70 into the valley of the Middle Fork Feather River, which takes it southeast to Blairsden, where the State Scenic Highway ends and State Route 89 splits to the south, and then east, through the Plumas National Forest, to Portola and Beckwourth. The large Sierra Valley begins at the latter community, and SR 70 heads almost directly across, passing the north end of SR 49 at Vinton and the south end of SR 284 at Chilcoot before crossing Beckwourth Pass, which the railroad takes the Chilcoot Tunnel under, and descending slightly to end at U.S. 395 at Hallelujah Junction.〔 The portion of SR 70 west of State Route 89 near Blairsden is also eligible for the State Scenic Highway System,〔(【引用サイトリンク】title=CA Codes (shc:260-284) )〕 but has not been designated as such by Caltrans. The entire route is part of the California Freeway and Expressway System,〔(【引用サイトリンク】title=CA Codes (shc:250-257) )〕 though it is mostly two lanes. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「California State Route 70」の詳細全文を読む スポンサード リンク
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